William Blair Funds N-CSRS Certified semi-annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act File Number 811-5344

William Blair Funds

(Exact name of registrant as specified in charter)

150 North Riverside Plaza, Chicago, IL	60606
(Address of principal executive offices)	(Zip Code)

Stephanie G. Braming, Principal Executive Officer
William Blair Funds
150 North Riverside Plaza, Chicago, IL 60606
(Name and address of agent for service)

Registrant’s telephone number, including area code: 312-236-1600

Date of fiscal year end: December 31

Date of reporting period: June 30, 2019

Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A Registrant is not required to respond to the collection of information contained in Form N-CSR unless the form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimates and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 100 F Street, NE, Washington, DC 20549. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. (ss) 3507.

Item 1. June 30, 2019 Semiannual Reports transmitted to shareholders.

		June 30, 2019
William Blair Funds Semiannual Report
	IMPORTANT NOTE: Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the William Blair Funds’ (the “Funds”) annual and semi-annual shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the shareholder reports from the Funds or from your financial intermediary, such as a broker-dealer or bank. Instead, shareholder reports will be available on the Funds’ website (https://www.williamblairfunds.com/investor_services/prospectus_reports_forms.fs), and you will be notified by mail each time a report is posted and provided with a website link to access the report. If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from the Funds electronically by notifying your financial intermediary or, if you are a direct investor, by calling 1-800-635-2886. You may elect to receive all future shareholder reports in paper free of charge. You can inform your financial intermediary that you wish to continue receiving paper copies of your shareholder reports, or if you are a direct investor, by calling 1-800-635-2886. Your election to receive reports in paper will apply to all Funds you hold directly or through your financial intermediary, as applicable.

Table of Contents
U.S. Growth Market Review and Outlook	6
U.S. Value Market Review and Outlook	7
Growth Fund
An Overview from the Portfolio Manager	8
Portfolio of Investments	10
Large Cap Growth Fund
An Overview from the Portfolio Managers	11
Portfolio of Investments	13
Mid Cap Growth Fund
An Overview from the Portfolio Managers	14
Portfolio of Investments	16
Small-Mid Cap Growth Fund
An Overview from the Portfolio Managers	17
Portfolio of Investments	19
Small-Mid Cap Value Fund
An Overview from the Portfolio Managers	20
Portfolio of Investments	22
Small Cap Growth Fund
An Overview from the Portfolio Managers	24
Portfolio of Investments	26
Small Cap Value Fund
An Overview from the Portfolio Managers	28
Portfolio of Investments	30
Global Markets Review and Outlook	32
Global Leaders Fund
An Overview from the Portfolio Managers	34
Portfolio of Investments	36
International Leaders Fund
An Overview from the Portfolio Managers	38
Portfolio of Investments	40
International Developed Plus Fund (In Liquidation)
An Overview from the Portfolio Managers	42
Portfolio of Investments	44
Institutional International Developed Plus Fund (In Liquidation)
An Overview from the Portfolio Managers	46
Portfolio of Investments	48
International Growth Fund
An Overview from the Portfolio Managers	50
Portfolio of Investments	52
Institutional International Growth Fund
An Overview from the Portfolio Managers	56
Portfolio of Investments	58
International Small Cap Growth Fund
An Overview from the Portfolio Managers	62
Portfolio of Investments	64

June 30, 2019 William Blair Funds 1

Emerging Markets Leaders Fund
An Overview from the Portfolio Managers	67
Portfolio of Investments	69
Emerging Markets Growth Fund
An Overview from the Portfolio Managers	71
Portfolio of Investments	73
Emerging Markets Small Cap Growth Fund
An Overview from the Portfolio Managers	77
Portfolio of Investments	79
Fixed Income Market Review and Outlook	83
Bond Fund
An Overview from the Portfolio Managers	85
Portfolio of Investments	87
Income Fund
An Overview from the Portfolio Manager	90
Portfolio of Investments	92
Low Duration Fund
An Overview from the Portfolio Managers	95
Portfolio of Investments	97
Macro Allocation Fund
An Overview from the Portfolio Managers	100
Portfolio of Investments	103
Financial Statements	107
Notes to Financial Statements	125
Financial Highlights	149
Renewal of the Management Agreement	188
Trustees and Officers	193
Fund Expenses	199

The views expressed in the commentary for each Fund reflect those of the portfolio management team only through the end of the period of the report as stated on the cover. The portfolio management team’s views are subject to change at any time based on market and other conditions and should not be construed as a recommendation. Statements involving predictions, assessments, analyses, or outlook for individual securities, industries, market sectors, and/or markets involve risks and uncertainties, and there is no guarantee they will come to pass.

This report is submitted for the general information of the shareholders of William Blair Funds. It is not authorized for distribution to prospective Fund investors unless accompanied or preceded by the Fund’s prospectus. Please carefully consider a Fund’s investment objectives, risks, charges, and expenses before investing. This and other information is contained in the Fund’s prospectus, which you may obtain by calling 1-800-742-7272. Read it carefully before you invest or send money.

2 Semiannual Report June 30, 2019

Performance as of June 30, 2019—Class N Shares (Unaudited)

						10 yr		Overall
	Year					(or since	Inception	Morningstar
	to Date	1 yr		3 yr	5 yr	inception)	Date	Rating
Growth Fund
Class N	22.38	14.07		17.32	11.44	13.87	3/20/1946	***
Morningstar Large Growth	21.11	10.02		16.97	11.33	14.71		Among 1,235
Russell 3000®Growth Index	21.41	10.60		17.81	13.02	16.13		Large Growth Funds
S&P 500®Index	18.54	10.42		14.19	10.71	14.70
Large Cap Growth Fund
Class N	24.10	16.01		20.40	14.73	16.11	12/27/1999	****
Morningstar Large Growth	21.11	10.02		16.97	11.33	14.71		Among 1,235
Russell 1000®Growth Index	21.49	11.56		18.07	13.39	16.28		Large Growth Funds
Mid Cap Growth Fund
Class N	27.40	12.75		15.38	9.88	13.42	2/1/2006	***
Morningstar Mid-Cap Growth	24.97	9.88		15.59	9.78	14.53		Among 539
Russell Midcap®Growth Index	26.08	13.94		16.49	11.10	16.02		Mid-Cap Growth Funds
Small-Mid Cap Growth Fund
Class N	24.27	9.65		18.07	12.99	15.99	12/29/2003	****
Morningstar Mid-Cap Growth	24.97	9.88		15.59	9.78	14.53		Among 539
Russell 2500TMGrowth Index	23.92	6.13		16.14	9.98	15.67		Mid-Cap Growth Funds
Small-Mid Cap Value Fund
Class N	16.67	(2.03	)	7.18	5.04	10.42	12/15/2011	***
Morningstar Small Blend	15.74	(3.76	)	10.09	5.65	—		Among 633
Russell 2500TMValue Index	15.26	(1.92	)	8.98	5.55	11.93		Small Blend Funds
Small Cap Growth Fund
Class N	18.98	0.89		19.06	11.20	14.31	12/27/1999	****
Morningstar Small Growth	21.82	3.22		16.12	9.18	14.47		Among 583
Russell 2000®Growth Index	20.36	(0.49	)	14.69	8.63	14.41		Small Growth Funds
Small Cap Value Fund
Class N	16.22	(3.35	)	7.48	4.87	12.18	12/23/1996	**
Morningstar Small Blend	15.74	(3.76	)	10.09	5.65	12.70		Among 633
Russell 2000®Value Index	13.47	(6.24	)	9.81	5.39	12.40		Small Blend Funds
Global Leaders Fund
Class N	20.66	4.14		13.86	8.11	11.89	10/15/2007	****
Morningstar World Large Stock	16.46	4.89		11.07	5.96	10.24		Among 722
MSCI ACW IMI (net)	16.07	4.56		11.42	6.03	10.32		World Large Stock Funds
International Leaders Fund
Class N	20.58	4.18		11.77	6.72	9.14	8/16/2012	****
Morningstar Foreign Large Growth	18.29	2.25		9.63	4.09	—		Among 396
MSCI ACW Ex-U.S. IMI (net)	13.33	0.26		9.17	2.25	5.96		Foreign Large Growth Funds

June 30, 2019 William Blair Funds 3

Performance as of June 30, 2019—Class N Shares (Unaudited)—continued

						10 yr		Overall
	Year					(or since	Inception	Morningstar
	to Date	1 yr		3 yr	5 yr	inception)	Date	Rating
International Developed Plus Fund
Class N	21.02	3.51		8.15	3.14	7.17	5/24/2004	**
Morningstar Foreign Large Growth	18.29	2.25		9.63	4.09	8.20		Among 396
MSCI World Ex-U.S. Index (net)	14.64	1.29		9.01	2.04	6.75		Foreign Large Growth Funds
International Growth Fund
Class N	19.27	(0.43	)	8.44	2.84	8.04	10/1/1992	***
Morningstar Foreign Large Growth	18.29	2.25		9.63	4.09	8.20		Among 396
MSCI ACW Ex-U.S. IMI (net)	13.33	0.26		9.17	2.25	6.78		Foreign Large Growth Funds
International Small Cap Growth Fund
Class N	18.73	(6.34	)	5.68	2.31	9.15	11/1/2005	**
Morningstar Foreign Small/Mid Growth	17.12	(4.52	)	9.50	4.65	10.59		Among 122
MSCI ACW Ex-U.S. Small Cap Index (net)	11.60	(5.94	)	7.76	2.77	8.48		Foreign Small/Mid Growth Funds
Emerging Markets Leaders Fund
Class N	16.71	3.20		9.74	2.56	3.50	5/3/2010	***
Morningstar Diversified Emerging Markets	12.06	1.16		8.92	1.71	—		Among 712
MSCI Emerging Markets Index (net)	10.58	1.21		10.66	2.49	2.97		Diversified Emerging Markets Funds
Emerging Markets Growth Fund
Class N	15.80	(2.03	)	9.20	2.27	6.94	6/6/2005	****
Morningstar Diversified Emerging Markets	12.06	1.16		8.92	1.71	5.82		Among 712
MSCI Emerging Markets IMI (net)	10.14	0.47		10.01	2.25	5.83		Diversified Emerging Markets Funds
Emerging Markets Small Cap Growth Fund
Class N	8.88	(8.06	)	3.04	1.24	7.92	10/24/2011	**
Morningstar Diversified Emerging Markets	12.06	1.16		8.92	1.71	—		Among 712
MSCI Emerging Markets Small Cap Index (net)	6.70	(5.12	)	5.46	0.53	3.41		Diversified Emerging Markets Funds
Bond Fund
Class N	8.05	7.89		2.74	2.80	4.62	5/1/2007	***
Morningstar Intermediate Core-Plus Bond	6.40	7.35		2.95	2.84	4.82		Among 539
Bloomberg Barclays U.S. Aggregate Index	6.11	7.87		2.31	2.95	3.90		Intermediate Core-Plus Bond Funds
Income Fund
Class N	4.33	4.60		1.45	1.63	3.07	10/1/1990	***
Morningstar Short-Term Bond	3.20	4.19		1.97	1.60	2.48		Among 478
Bloomberg Barclays Intermediate Government/Credit Bond Index	4.97	6.93		1.99	2.39	3.24		Short-Term Bond Funds

4 Semiannual Report June 30, 2019

Performance as of June 30, 2019—Class N Shares (Unaudited)—continued

					10 yr		Overall
	Year				(or since	Inception	Morningstar
	to Date	1 yr	3 yr	5 yr	inception)	Date	Rating
Low Duration Fund
Class N	2.46	2.97	1.38	1.14	1.21	12/1/2009	**
Morningstar Ultrashort Bond	1.85	2.76	1.85	1.32	—		Among 151
Bank of America Merrill Lynch 1-Year U.S. Treasury Note Index	1.76	2.98	1.43	1.02	0.73		Ultrashort Bond Funds
Macro Allocation Fund
Class N	2.45	2.77	2.63	0.43	4.35	11/29/2011	**
Morningstar Multialternative	5.39	1.81	2.85	1.19	—		Among 265
Bank of America Merrill Lynch 3-Month U.S. Treasury Bill Index	1.24	2.31	1.38	0.87	0.60		Multialternative Funds

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted.Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or a loss when you sell shares.For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers, performance would be lower. Investing in smaller companies involves special risks, including higher volatility and lower liquidity. International and emerging markets investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. As interest rates rise, bond prices will typically fall and bond funds may become more volatile.Class N shares are available to the general public without a sales load.

Morningstar Ratings^TMare as of 6/30/2019 and are subject to change every month. The ratings are based on a risk-adjusted return measure that accounts for variation in a fund’s monthly performance, placing more emphasis on downward variations and rewarding consistent performance. The top 10% of funds in each Category receive 5 stars, the next 22.5% receive 4 stars, the middle 35% receive 3 stars, the next 22.5% receive 2 stars, and the bottom 10% receive 1 star. The Overall Morningstar Rating for a fund is derived from a weighted-average of the performance figures associated with its three-, five- and ten-year (if applicable) Morningstar Rating metrics. The 3/5/10 year Morningstar ratings were as follows: Growth Fund ***/***/** and Large Cap Growth Fund ****/*****/**** out of 1,235/1,100/812 large growth funds; Mid Cap Growth Fund ***/***/*** and Small-Mid Cap Growth Fund ****/****/**** out of 539/484/367 mid-cap growth funds; Small Cap Growth Fund ****/****/***, out of 583/515/393 small growth funds; Small-Mid Cap Value Fund **/***/NA and Small Cap Value Fund **/**/** out of 633/516/375 small blend funds; Global Leaders Fund ****/****/**** out of 722/594/350 world large stock funds; International Developed Plus Fund **/***/**, International Growth Fund **/**/***, and International Leaders Fund ****/****/NA out of 396/336/247 foreign large growth funds; International Small Cap Growth Fund */*/*** out of 122/99/59 foreign small/mid growth funds; Emerging Markets Leaders Fund ***/***/****, Emerging Markets Growth Fund ***/***/****, and Emerging Markets Small Cap Growth */***/NA out of 712/560/240 diversified emerging markets funds; Bond Fund ***/***/*** out of 539/453/332 intermediate core-plus bond funds; Income Fund **/***/**** out of 478/421/269 short-term bond funds; Low Duration Fund **/**/NA out of 151/128/NA ultrashort bond funds; and Macro Allocation Fund ***/**/NA out of 265/177/NA multialternative funds.

Please carefully consider a Fund’s investment objectives, risks, charges, and expenses before investing. This and other information is contained in the Fund’s prospectus, which you may obtain by calling 1-800-742-7272. Read it carefully before you invest or send money.

June 30, 2019 William Blair Funds 5

U.S. Growth Market Review and Outlook

Following a pronounced sell-off to end 2018, U.S. equities had a strong start to 2019. Spurring the first quarter recovery were comments from the Federal Open Market Committee (“FOMC”) indicating that it would be patient and flexible with future monetary policy decisions. A solid U.S. economic backdrop and healthy corporate earnings trends further supported the market.

Relative to the robust first quarter, positive performance was more moderate in the second quarter of 2019 and included significant swings on a monthly basis. U.S. corporations reported first quarter earnings that were broadly better than investors’ previously-lowered expectations, providing support for equities to move higher during the month of April. From there, macro considerations, most notably rising trade tensions and a perceived shift in U.S. Federal Reserve (the “Fed”) policy, seemed to drive the direction of the market. As trade threats dominated the news, rising investor angst around the possible impacts of protectionism on global economic growth and corporate earnings corresponded with a decline in equities. A subsequent recovery during the month of June was helped by the perception of a shift in Fed policy and its increased willingness to cut interest rates if economic conditions deteriorate.

While equities moved higher over the course of the second quarter, the 10 year Treasury yield declined and the 10 year to 3 month yield curve inverted, which some view as a leading indicator of a potential recession. Further supporting the notion of slowing economic growth, U.S. manufacturing activity weakened, while growth in housing prices slowed. However, strength in consumption and retail sales, bolstered by low unemployment and moderate wage growth, allowed investors to look through some of the more cautionary indicators, bringing U.S. equities back near all-time highs to close out the second quarter.

Despite strong equity market performance during the first half of 2019, many of the risks that contributed to the late 2018 selloff remain on the horizon. From a Fed policy perspective, it is not clear how much impact the interest rate increases implemented in 2017 and 2018 will have on the economy or how effective monetary policy will be in stimulating the economy from here, given that financial conditions are already quite supportive. Global interest rates have declined year-to-date with continued monetary stimulus from China and other central banks. In addition, the Fed faces the challenge of managing the economy against investor expectations, which call for several interest rate cuts over the next twelve months, and a trade policy that is in flux and could ultimately have varying effects on U.S. economic growth. In the meantime, tariff uncertainty can have a real economic impact by disrupting supply chains and causing corporations to delay investment activity. Ongoing trade negotiations, as well as political disruption leading into the 2020 U.S. presidential election, are likely to result in continued market volatility.

Balancing some of these uncertainties are data points that indicate a still healthy U.S. economy, now in its eleventh year of expansion. The labor market, in particular, remains robust with continued low unemployment and moderate wage growth. U.S. consumer confidence remains high and spending healthy, while corporate bond yields have declined, reducing interest expense for corporations. Corporate profit margins are strong, notwithstanding the fact that they broadly contracted during the second quarter of 2019 as many companies have not been able to fully offset wage growth and higher input costs with price increases. We feel relatively well positioned in this regard as our investment approach has always emphasized companies with strong value propositions that enable better than average pricing flexibility.

We believe our longstanding focus on identifying durable businesses, whose stocks present attractive risk/reward opportunities, will serve us well in an environment of uncertainty where business fundamentals are especially important.

6 Semiannual Report June 30, 2019

U.S. Value Market Review and Outlook

U.S. equities drifted higher during the second quarter of 2019, adding to the robust returns from earlier in the year. The dramatic bounce-back from a dismal finish to 2018 was largely the result of a dovish pivot by the Federal Reserve (“Fed”) and the Fed’s lack of commitment to future rate moves as it takes a more patient approach to future monetary policy decisions. Healthy corporate earnings and expectations for a trade deal between the U.S. and China helped boost investor confidence and fueled strong U.S. equity returns early in the year.

In contrast to the robust returns in the first quarter of 2019, positive market performance was more moderate during the second quarter. Although corporate earnings growth continued to be solid and contributed to positive market performance in April, relatively uninspiring economic data and increased geopolitical instability, mainly around trade, seemed to temper returns during the quarter. As the exchanges surrounding trade intensified and dominated the news, bond yields plummeted as concerns regarding the potential implications of protectionism on global economic growth and corporate earnings contributed to the market decline in May. Late in the quarter, the Fed signaled its willingness to lower short-term interest rates in an effort to sustain economic expansion, which was positively received by investors. Generally speaking, it appears that a more dovish Fed and its patience regarding future monetary policy decisions is helping to offset a more volatile trade situation overall.

Despite the strong rebound in U.S. equity performance through the second quarter, many of the risks that contributed to the dramatic market sell-off late in 2018 remain intact. The constantly evolving trade/tariff landscape seems to present a challenge for the Fed and complicates future monetary policy decisions as it is forced to make assumptions about harder-to-predict geopolitical risks and their impact on the economy. Continued trade policy uncertainty may result in supply chain disruption and delayed corporate investment activity, which could alter the trajectory of global growth. The Fed may be proactive and move more quickly than in previous cycles in an effort to spark growth and prolong the current economic expansion.

We remain cognizant that corporate debt levels continue to rise and could contribute to higher market volatility should these more highly levered companies feel pressure as a greater percentage of their cash flow is needed to service their rising debt levels. The main difference between this cycle and what transpired during the global financial crisis is that these higher debt levels are not on bank balance sheets, but rather have been privately financed. Should these lower quality/more highly levered companies have trouble accessing the capital markets or get squeezed as high yield spreads increase, this could be the impetus for sustained higher quality stock outperformance. We remain focused on companies with solid balance sheets and have gravitated towards companies with even stronger balance sheets given our concern about corporate debt levels and expectations for increased market volatility. As always, our focus remains on identifying quality companies at discount prices and corporate transformation opportunities. We continue to find opportunities across multiple sectors and believe the Fund is well-suited to withstand a variety of market scenarios and add value over the long-term.

June 30, 2019 William Blair Funds 7

	Growth Fund
	The Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGER
David C. Fording	The William Blair Growth Fund (Class N shares) posted a 22.38% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 3000®Growth Index (the “Index”), increased 21.41%. Outperformance for the year-to-date period was driven by stock selection and a tailwind for our investment style. From a stock selection perspective, Industrials and Health Care were standout sectors, in part due to our positions in CoStar Group, Inc. (Industrials), Copart, Inc. (Industrials) and Veeva Systems, Inc. (Health Care). Real estate information services company CoStar Group advanced on business trends that were consistent with our investment thesis, including strong growth in its commercial real estate business and continued market share gains in its apartment rental advertising business. Other top contributors were metal packaging provider Ball Corporation (Materials), as strong demand drove volume growth for aluminum cans, and Worldpay, Inc. (Information Technology). From a style perspective, our higher valuation exposure, driven by the Fund’s quality growth bias, was a tailwind as stocks with higher valuations generally outperformed during the period. Conversely, top detractors from performance year-to-date included Healthcare Services Group, Inc. (Industrials), UnitedHealth Group, Inc. (Health Care), Pure Storage, Inc. (Information Technology) and Weight Watchers International, Inc. (Consumer Discretionary). Healthcare Services Group provides outsourced housekeeping, facility maintenance and food services to nursing homes and other care facilities. The stock’s underperformance was most notable during the first quarter, as the company reported revenue that disappointed investors and was attributable to a contract change with one of its food service customers that would dampen revenue, but ultimately lift margins. In addition, the Communication Services sector was a detractor as our position in Alphabet, Inc. and not owning Facebook, Inc. contributed to lagging returns in the sector. We sold Facebook in late 2018 on concerns over slowing revenue growth, margin compression and stepped up regulatory scrutiny around privacy and use of personal data; the latter of which remains a fundamental threat to Facebook’s long term business model. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 6 for additional information.

8 Semiannual Report June 30, 2019

Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		22.38	%		14.07	%		17.32	%		11.44	%		13.87	%		—
Class I		22.59			14.43			17.66			11.77			14.23			—
Class R6		—			—			—			—			—			2.53	%
Russell 3000® Growth Index		21.41			10.60			17.81			13.02			16.13			0.81
S&P 500®Index		18.54			10.42			14.19			10.71			14.70			1.00

(a) Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 3000^® Growth Index consists of large, medium, and small capitalization companies with above average price-to-book ratios and forecasted growth rates. The index is weighted by market capitalization and large/medium/small companies make up approximately 80%/15%/5% of the index.

The S&P 500^® Index indicates broad larger capitalization equity market performance.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

 

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 9

Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Information Technology—30.1%
*	Adobe, Inc.		17,315	$	5,102
*	Arista Networks, Inc.		7,980		2,072
	Booz Allen Hamilton Holding Corporation		64,052		4,241
	Dolby Laboratories, Inc.		57,743		3,730
	Genpact, Ltd.†		89,815		3,421
*	Guidewire Software, Inc.		25,832		2,619
	Mastercard, Inc. Class “A”		45,773		12,108
*	MaxLinear, Inc.		86,201		2,021
	Microsoft Corporation		159,227		21,330
	National Instruments Corporation		58,571		2,459
*	Pure Storage, Inc.		162,374		2,479
*	Rogers Corporation		10,013		1,728
	Sabre Corporation		150,569		3,343
	Texas Instruments, Inc.		47,508		5,452
*	Verra Mobility Corporation		146,920		1,923
*	Worldpay, Inc. Class “A”		34,044		4,172
					78,200
	Consumer Discretionary—15.2%
	Advance Auto Parts, Inc.		18,432		2,841
*	Amazon.com, Inc.		9,185		17,393
*	Burlington Stores, Inc.		27,931		4,752
	Domino’s Pizza, Inc.		8,959		2,493
*	Grand Canyon Education, Inc.		28,985		3,392
*	GrubHub, Inc.		27,027		2,108
*	Laureate Education, Inc.		175,293		2,754
*	Ulta Salon Cosmetics & Fragrance, Inc.		11,249		3,902
					39,635
	Health Care—14.5%
*	Veeva Systems, Inc. Class “A”		17,918		2,905
	Abbott Laboratories		48,107		4,046
*	ABIOMED, Inc.		10,029		2,612
	Agilent Technologies, Inc.		34,104		2,547
*	Codexis, Inc.		72,198		1,331
*	Horizon Therapeutics plc†		96,598		2,324
*	Portola Pharmaceuticals, Inc.		72,527		1,968
	Stryker Corporation		19,800		4,070
	Teleflex, Inc.		7,798		2,582
	UnitedHealth Group, Inc.		36,212		8,836
	Zoetis, Inc.		39,750		4,511
					37,732
	Industrials—11.4%
	BWX Technologies, Inc.		116,151		6,051
*	Copart, Inc.		65,272		4,878
*	CoStar Group, Inc.		9,651		5,347
	Healthcare Services Group, Inc.		77,543		2,351
	Luxfer Holdings plc†		61,357		1,505
	Raytheon Co.		26,878		4,674
*	The Middleby Corporation		23,790		3,228
*	Trex Co., Inc.		20,779		1,490
					29,524

		Shares or
		Principal
	Issuer	Amount		Value
	Common Stocks—(continued)
	Communication Services—9.9%
	Activision Blizzard, Inc.		68,249	$	3,221
*	Alphabet, Inc. Class “A”		14,876		16,108
*	Cars.com, Inc.		51,495		1,016
*	Live Nation Entertainment, Inc.		47,354		3,137
*	Take-Two Interactive Software, Inc.		19,122		2,171
					25,653
	Consumer Staples—7.6%
	Costco Wholesale Corporation		21,306		5,630
*	Primo Water Corporation		135,512		1,667
	The Coca-Cola Co.		161,109		8,204
	The Estee Lauder Cos., Inc. Class “A”		22,986		4,209
					19,710
	Financials—5.3%
	East West Bancorp, Inc.		48,408		2,264
*	Encore Capital Group, Inc.		49,311		1,670
	Intercontinental Exchange, Inc.		84,168		7,233
	Virtu Financial, Inc.		123,894		2,699
					13,866
	Materials—4.6%
	Ball Corporation		98,773		6,913
	Linde plc†		24,618		4,943
					11,856
	Energy—0.8%
	Cameco Corporation†		190,907		2,049
	Total Common Stocks—99.4% (cost $168,795)				258,225
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $1,760, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$1,760		1,760
	Total Repurchase Agreement—0.7% (cost $1,760)				1,760
	Total Investments—100.1% (cost $170,555)				259,985
	Liabilities, plus cash and other assets—(0.1)%				(201	)
	Net assets—100.0%			$	259,784

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

10 Semiannual Report June 30, 2019

	Large Cap Growth Fund
	The Large Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
James S. Golan David P. Ricci	The William Blair Large Cap Growth Fund (Class N shares) posted a 24.10% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 1000®Growth Index (the “Index”), increased 21.49%. Outperformance for the year-to-date period was driven by stock selection and a tailwind for our investment style. From a stock selection perspective, Industrials and Health Care were standout sectors, in part due to our positions in Copart, Inc. (Industrials), Equifax, Inc. (Industrials) and Veeva Systems, Inc. (Health Care). Veeva Systems and Copart were easily the Fund’s top contributors during the period as generally strong business fundamentals persisted year-to-date. Shares of Copart, an online auction platform for salvage vehicles, outperformed as a growing buyer base drove higher average selling prices and as Copart raised buyer fees on select vehicles. Veeva Systems, a cloud-based software and data solutions provider primarily for the life sciences industry, outperformed after reporting record-high customer additions and strong subscription revenue growth. Other notable contributors to performance were PayPal Holdings, Inc. (Information Technology) and The Estee Lauder Cos., Inc. (Consumer Staples). From a style perspective, our higher valuation exposure, driven by the Fund’s quality growth bias, was a tailwind as stocks with higher valuations generally outperformed during the period. Conversely, top detractors from performance year-to-date included advanced medical technologies company, ABIOMED, Inc. (Health Care), UnitedHealth Group, Inc. (Health Care) and Red Hat, Inc. (Information Technology). ABIOMED underperformed as uncertainty related to FDA guidance around the appropriate patient population for its Impella heart pump caused shares to decline. Concern around a potential competitive entrant also pressured shares of ABIOMED during the first quarter. Communication Services was also a detractor as our positions in Alphabet, Inc. and Activision Blizzard, Inc., as well as not owning Facebook, Inc., contributed to lagging returns in the sector. We sold Facebook in late 2018 on concerns over slowing revenue growth, margin compression, governance issues and stepped up regulatory scrutiny around privacy and use of personal data; the latter of which remains a fundamental threat to Facebook’s long term business model. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 6 for additional information.

June 30, 2019 William Blair Funds 11

Large Cap Growth Fund

Performance Highlights (Unaudited)

 

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		24.10	%		16.01	%		20.40	%		14.73	%		16.11	%		—
Class I		24.25			16.32			20.73			15.02			16.39			—
Class R6		—			—			—			—			—			4.03	%
Russell 1000® Growth Index		21.49			11.56			18.07			13.39			16.28			0.81

(a)  Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 1000^®Growth Index consists of large capitalization companies with above average price-to-book ratios and forecasted growth rates.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

12 Semiannual Report June 30, 2019

Large Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Information Technology—30.9%
	Accenture plc†		45,790	$	8,461
*	Adobe, Inc.		23,900		7,042
*	Guidewire Software, Inc.		44,980		4,560
	Intuit, Inc.		26,230		6,855
	Mastercard, Inc.		30,810		8,150
	Microsoft Corporation		151,020		20,231
*	PayPal Holdings, Inc.		75,950		8,693
	Texas Instruments, Inc.		63,170		7,249
					71,241
	Health Care—17.2%
	Abbott Laboratories		69,920		5,880
*	ABIOMED, Inc.		15,010		3,910
	Stryker Corporation		28,260		5,810
	UnitedHealth Group, Inc.		42,190		10,295
*	Veeva Systems, Inc. Class “A”		36,830		5,970
	Zoetis, Inc.		68,360		7,758
					39,623
	Communication Services—12.4%
	Activision Blizzard, Inc.		112,880		5,328
*	Alphabet, Inc. Class “A”		9,410		10,189
*	Alphabet, Inc. Class “C”		4,096		4,428
*	Live Nation Entertainment, Inc.		75,340		4,991
*	Netflix, Inc.		10,040		3,688
					28,624
	Consumer Discretionary—11.9%
*	Amazon.com, Inc.		9,320		17,648
	McDonald’s Corporation		20,080		4,170
	Starbucks Corporation		67,360		5,647
					27,465
	Consumer Staples—9.5%
	Costco Wholesale Corporation		18,070		4,775
*	Monster Beverage Corporation		99,810		6,371
	The Coca-Cola Co.		100,190		5,102
	The Estee Lauder Cos., Inc. Class “A”		30,160		5,522
					21,770
	Industrials—9.4%
*	Copart, Inc.		86,330		6,452
	Equifax, Inc.		43,010		5,817
	Fortive Corporation		42,100		3,432
	Raytheon Co.		33,960		5,905
					21,606
	Financials—4.7%
	Aon plc†		24,530		4,734
	Intercontinental Exchange, Inc.		72,200		6,205
					10,939
	Materials—2.9%
	Linde plc†		32,730		6,573
	Total Common Stocks—98.9% (cost $156,334)				227,841

Issuer	Principal Amount			Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $2,803, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$2,803	$	2,803
Total Repurchase Agreement—1.2% (cost $2,803)				2,803
Total Investments—100.1% (cost $159,137)				230,644
Liabilities, plus cash and other assets—(0.1)%				(242	)
Net assets—100.0%			$	230,402

† = U.S. listed foreign security

* = Non-income producing security

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 13

	Mid Cap Growth Fund
	The Mid Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Daniel Crowe Robert C. Lanphier, IV	The William Blair Mid Cap Growth Fund (Class N shares) posted a 27.40% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell Midcap®Growth Index (the “Index”), increased 26.08%. With the Index up approximately 26% year-to-date, Fund outperformance over the period was driven by strong stock selection. The Fund generally lagged during the strongest periods of benchmark returns, but that was more than offset by outperformance during other periods and attributable to the generally strong fundamental performance of the companies held by the Fund. Stock selection in the Industrials sector was a standout contributor to performance, in part due to our positions in CoStar Group, Inc. and Copart, Inc. Real estate information services company CoStar Group outperformed on business trends that were consistent with our investment thesis, including strong growth in its commercial real estate business and continued market share gains in its apartment rental advertising business. Other top contributors were metal packaging provider, Ball Corporation (Materials), Worldpay, Inc. (Information Technology) and Wayfair, Inc. (Consumer Discretionary). Ball Corporation benefited as strong demand drove volume growth for aluminum cans. Conversely, top detractors from performance year-to-date included Lamb Weston Holdings, Inc. (Consumer Staples) and Pure Storage, Inc. (Information Technology). Flash-based storage solutions provider Pure Storage underperformed due to an increased focus on large enterprise accounts with lengthened sales cycles. Shares of potato processor Lamb Weston were weighed down as some investors became concerned that incremental industry capacity coming online over the next two years could pressure margins. Other notable laggards were Health Care holdings Centene Corporation and ABIOMED, Inc. In addition, stock selection in Financials, including our position in Cboe Global Markets, Inc., detracted from relative results. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 6 for additional information.

14 Semiannual Report June 30, 2019

Mid Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		27.40	%		12.75	%		15.38	%		9.88	%		13.42	%		—
Class I		27.43			13.05			15.67			10.15			13.71			—
Class R6		—			—			—			—			—			2.01	%
Russell Midcap® Growth Index		26.08			13.94			16.49			11.10			16.02			1.99

(a)  Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in medium capitalization companies involves special risks, including higher volatility and lower liquidity. Medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell Midcap^®Growth Index is an index that is constructed to provide a comprehensive and unbiased barometer of the mid-cap growth market.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 15

Mid Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Information Technology—27.1%
*	Advanced Micro Devices, Inc.		40,575	$	1,232
*	Arista Networks, Inc.		2,860		742
*	Autodesk, Inc.		9,900		1,613
	Booz Allen Hamilton Holding Corporation		19,084		1,264
	Dolby Laboratories, Inc.		19,885		1,285
*	EPAM Systems, Inc.		4,945		856
	Global Payments, Inc.		11,100		1,777
*	GoDaddy, Inc.		17,745		1,245
*	Guidewire Software, Inc.		6,863		696
	j2 Global, Inc.		7,265		646
	MAXIMUS, Inc.		11,705		849
	Microchip Technology, Inc.		15,980		1,385
*	Pure Storage, Inc.		58,910		900
	Sabre Corporation		63,008		1,399
*	WEX, Inc.		8,570		1,783
*	Worldpay, Inc. Class “A”		7,694		943
					18,615
	Industrials—18.4%
	BWX Technologies, Inc.		39,044		2,034
*	Copart, Inc.		28,200		2,108
*	CoStar Group, Inc.		3,709		2,055
	Equifax, Inc.		9,785		1,323
	Fortive Corporation		16,125		1,314
*	The Middleby Corporation		10,250		1,391
	Verisk Analytics, Inc.		3,500		513
	Waste Connections, Inc.†		11,585		1,107
	Xylem, Inc.		9,800		820
					12,665
	Consumer Discretionary—15.5%
	Advance Auto Parts, Inc.		8,470		1,305
	Aptiv plc†		7,965		644
*	Burlington Stores, Inc.		9,655		1,643
*	CarMax, Inc.		10,575		918
	Domino’s Pizza, Inc.		2,080		579
	Ross Stores, Inc.		11,410		1,131
	Service Corporation International		20,200		945
*	Ulta Salon Cosmetics & Fragrance, Inc.		4,235		1,469
	Vail Resorts, Inc.		6,035		1,347
*	Wayfair, Inc.		4,395		642
					10,623
	Health Care—14.6%
*	ABIOMED, Inc.		3,600		938
	Agilent Technologies, Inc.		15,410		1,151
*	Align Technology, Inc.		3,010		824
*	Centene Corporation		21,826		1,144
*	DexCom, Inc.		2,805		420
	Encompass Health Corporation		18,385		1,165
*	IDEXX Laboratories, Inc.		2,890		796
*	Mettler-Toledo International, Inc.		1,405		1,180
	Teleflex, Inc.		4,335		1,435
*	Veeva Systems, Inc. Class “A”		5,941		963
					10,016

	Issuer	Shares or Principal Amount		Value
	Common Stocks—(continued)
	Financials—7.9%
	Arthur J Gallagher & Co.		19,130	$	1,675
	Cboe Global Markets, Inc.		13,005		1,348
	East West Bancorp, Inc.		21,450		1,003
	Signature Bank		4,980		602
*	SVB Financial Group		3,625		814
					5,442
	Materials—7.1%
	Ball Corporation		33,950		2,376
	Celanese Corporation		6,920		746
	Vulcan Materials Co.		12,715		1,746
					4,868
	Communication Services—3.4%
*	Live Nation Entertainment, Inc.		15,910		1,054
*	Take-Two Interactive Software, Inc.		11,520		1,308
					2,362
	Consumer Staples—3.2%
	Conagra Brands, Inc.		32,000		849
	Lamb Weston Holdings, Inc.		20,835		1,320
					2,169
	Real Estate—1.4%
*	SBA Communications Corporation		4,260		958
	Energy—0.9%
*	Parsley Energy, Inc.		34,380		654
	Total Common Stocks—99.5% (cost $55,237)				68,372
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $925, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$925		925
	Total Repurchase Agreement—1.3% (cost $925)				925
	Total Investments—100.8% (cost $56,162)				69,297
	Liabilities, plus cash and other assets—(0.8)%				(550	)
	Net assets—100.0%			$	68,747

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

16 Semiannual Report June 30, 2019

	Small-Mid Cap Growth Fund
	The Small-Mid Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Daniel Crowe   Robert C. Lanphier, IV	The William Blair Small-Mid Cap Growth Fund (Class N shares) posted a 24.27% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 2500TMGrowth Index (the “Index”), increased 23.92%. The Fund outperformed for the year-to-date period as stock selection and a tailwind for our investment style contributed to excess returns. From a stock selection perspective, selection in the Industrials and Health Care sectors was positive, helped by positions in CoStar Group, Inc. (Industrials), Copart, Inc. (Industrials) and Catalent, Inc. (Health Care). Real estate information services company CoStar Group advanced on business trends that were consistent with our investment thesis, including strong growth in its commercial real estate business and continued share gains in its apartment rental advertising business. Outperformance from Information Technology holdings Euronet Worldwide, Inc. and Rogers Corporation also added to relative returns. Shares of Euronet Worldwide, an electronic payment and transaction processing solutions company, advanced as all three business segments performed well and the company disclosed details about a new cloud-based payments platform which could add to growth over the long term. From a style perspective, our typical larger market cap bias provided a tailwind as the larger cap stocks within our small-mid cap universe outperformed the smaller cap stocks. This year-to-date style dynamic was strongest during the second quarter. Top detractors from performance during the period included Inogen, Inc. (Health Care), Healthcare Services Group, Inc. (Industrials), Pure Storage, Inc. (Information Technology) and Lamb Weston Holdings, Inc. (Consumer Staples). Shares of Inogen, a manufacturer of portable oxygen concentrators, underperformed on a decline in sales growth that resulted from the combination of lower sales productivity and a large customer that was restructuring. In addition, our Consumer Discretionary holdings lagged those of the benchmark. Notable among them was Adtalem Global Education, Inc., which underperformed due to lowered earnings expectations for its Brazil programs and escalating rhetoric around free education ahead of the forthcoming U.S. presidential primaries. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 6 for additional information.

June 30, 2019 William Blair Funds 17

Small-Mid Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		24.27	%		9.65	%		18.07	%		12.99	%		15.99	%		—
Class I		24.46			9.91			18.37			13.29			16.28			—
Class R6		—			—			—			—			—			2.91	%
Russell 2500TM Growth Index		23.92			6.13			16.14			9.98			15.67			1.81

(a)  Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 2500^TMGrowth Index measures the performance of those Russell 2500 companies with above average price-to-book ratios and forecasted growth rates.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

18 Semiannual Report June 30, 2019

Small-Mid Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Industrials—22.5%
	BWX Technologies, Inc.		1,558,221	$	81,183
*	Copart, Inc.		1,150,220		85,967
*	CoStar Group, Inc.		77,938		43,182
*	Genesee & Wyoming, Inc.		350,736		35,074
	Healthcare Services Group, Inc.		934,721		28,341
	HEICO Corporation		428,457		44,290
	Ritchie Bros Auctioneers, Inc.†		806,250		26,784
*	SiteOne Landscape Supply, Inc.		323,681		22,431
*	Teledyne Technologies, Inc.		208,751		57,171
	The Brink’s Co.		345,000		28,007
*	The Middleby Corporation		346,137		46,971
	The Toro Co.		178,063		11,912
	TransUnion		850,076		62,489
*	Trex Co., Inc.		908,763		65,158
					638,960
	Information Technology—22.1%
*	Aspen Technology, Inc.		430,563		53,510
*	Avalara, Inc.		474,308		34,245
	Booz Allen Hamilton Holding Corporation		799,236		52,917
*	Euronet Worldwide, Inc.		545,604		91,793
*	GoDaddy, Inc.		554,737		38,915
*	Guidewire Software, Inc.		274,787		27,858
	j2 Global, Inc.		312,415		27,771
*	MaxLinear, Inc.		581,160		13,622
	National Instruments Corporation		590,876		24,811
*	Nice, Ltd.-ADR		323,640		44,339
*	Novanta, Inc.†		242,277		22,847
*	Pure Storage, Inc.		2,801,019		42,772
*	Qualys, Inc.		309,122		26,918
*	Rogers Corporation		286,419		49,430
	Sabre Corporation		1,621,125		35,989
*	WEX, Inc.		193,803		40,330
					628,067
	Health Care—21.4%
*	ABIOMED, Inc.		157,000		40,897
*	Amedisys, Inc.		238,400		28,944
*	Cambrex Corporation		589,830		27,610
*	Catalent, Inc.		563,959		30,572
*	DexCom, Inc.		116,498		17,456
	Encompass Health Corporation		828,504		52,494
*	Exact Sciences Corporation		271,368		32,032
*	Glaukos Corporation		593,968		44,785
*	Halozyme Therapeutics, Inc.		865,956		14,877
*	Horizon Therapeutics plc†		1,574,146		37,874
*	Inspire Medical Systems, Inc.		257,454		15,615
*	Insulet Corporation		638,567		76,232
*	Ligand Pharmaceuticals, Inc.		208,886		23,844
*	Penumbra, Inc.		259,356		41,497
*	Portola Pharmaceuticals, Inc.		1,117,940		30,330
*	STERIS plc†		275,844		41,068
	Teleflex, Inc.		155,548		51,510
					607,637

	Issuer	Shares or Principal Amount		Value
	Common Stocks—(continued)
	Consumer Discretionary—10.3%
*	Adtalem Global Education, Inc.		1,063,747	$	47,922
*	Burlington Stores, Inc.		419,546		71,386
	Domino’s Pizza, Inc.		138,204		38,459
*	Grand Canyon Education, Inc.		565,020		66,119
	Vail Resorts, Inc.		192,788		43,026
*	Wayfair, Inc.		182,675		26,671
					293,583
	Financials—8.3%
	BrightSphere Investment Group plc†		1,012,271		11,550
	Cboe Global Markets, Inc.		592,080		61,357
	East West Bancorp, Inc.		885,718		41,425
*	Encore Capital Group, Inc.		689,276		23,346
	FirstCash, Inc.		455,138		45,523
	Signature Bank		207,400		25,062
	Virtu Financial, Inc.		1,260,564		27,455
					235,718
	Materials—3.9%
*	Axalta Coating Systems, Ltd.†		794,580		23,655
*	Crown Holdings, Inc.		390,536		23,862
	Martin Marietta Materials, Inc.		274,280		63,114
					110,631
	Communication Services—3.3%
	Cable One, Inc.		29,958		35,080
*	Live Nation Entertainment, Inc.		877,916		58,162
					93,242
	Consumer Staples—3.1%
*	BJ’s Wholesale Club Holdings, Inc.		1,335,347		35,253
	Lamb Weston Holdings, Inc.		809,146		51,268
					86,521
	Real Estate—2.4%
	Colliers International Group, Inc.†		224,479		16,077
	FirstService Corporation†		338,448		32,464
	Jones Lang LaSalle, Inc.		134,588		18,935
					67,476
	Energy—0.6%
*	Parsley Energy, Inc.		863,444		16,414
	Total Common Stocks—97.9% (cost $2,306,990)				2,778,249
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $58,029, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$58,026		58,026
	Total Repurchase Agreement—2.0% (cost $58,026)				58,026
	Total Investments—99.9% (cost $2,365,016)				2,836,275
	Cash and other assets, less liabilities—0.1%				3,086
	Net assets—100.0%			$	2,839,361

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 19

	Small-Mid Cap Value Fund
	The Small-Mid Cap Value Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Chad M. Kilmer Mark T. Leslie David S. Mitchell	The William Blair Small-Mid Cap Value Fund (Class N shares) posted a 16.67% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 2500TMValue Index (the “Index”), increased 15.26%. The Fund’s outperformance relative to the Index was due to the combination of stock selection and style tailwinds given the strategy’s higher growth profile and lack of exposure to deeper value stocks. At the sector level, the most significant contributor to the Fund’s relative performance was Industrials due to strong stock selection within Road & Rail, Machinery, and Building Products. Within Information Technology, the best performing sector of the market during the period, the Fund’s relative performance was primarily the result of strong stock selection within Software. Strong stock selection within Banks and Diversified Financial Services contributed to the relative returns within Financials. Consumer Discretionary was the most significant detractor from the Fund’s relative returns due to stock selection within Diversified Consumer Services and Hotels, Restaurants & Leisure. The relative underperformance within Energy was the result of stock selection within Oil & Gas Exploration & Production. The Fund’s relative performance within Consumer Staples, the worst performing sector of the market during the period, was driven by stock selection within Packaged Food & Meats. Looking specifically at stock selection, the Fund’s largest contributors to relative performance were Gardner Denver Holdings, Inc. (Industrials), Booz Allen Hamilton Holding Corporation (Information Technology), and TopBuild Corporation (Consumer Discretionary). Offsetting these contributors were our investments in Whiting Petroleum Corporation (Energy), Lamb Weston Holdings, Inc. (Consumer Staples), and Range Resources Corporation (Energy). Please refer to the U.S. Value Market Review and Outlook relating to the Fund on page 7 for additional information.

20 Semiannual Report June 30, 2019

Small-Mid Cap Value Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		16.67	%		(2.03	)%		7.18	%		5.04	%		10.42	%
Class I(a)		16.79			(1.73	)		7.45			5.32			10.72
Russell 2500TMValue Index(a)		15.26			(1.92	)		8.98			5.55			11.93
Class R6(b)		—			—			—			—			(1.28	)
Russell 2500TMValue Index(b)		—			—			—			—			(0.73	)

(a)	Since inception is for the period from December 15, 2011 (Commencement of Operations) to June 30, 2019.
(b)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 2500^TMValue Index consists of small to mid-capitalization companies with below average price-to-book ratios and forecasted growth rates.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 21

Small-Mid Cap Value Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Financials—22.4%
	American Financial Group, Inc.		185	$	19
	CNO Financial Group, Inc.		865		14
	E*TRADE Financial Corporation		308		14
	East West Bancorp, Inc.		394		18
	First American Financial Corporation		275		15
	FNB Corporation		1,594		19
	Hancock Whitney Corporation		416		17
	Hanover Insurance Group, Inc.		174		22
	Home BancShares, Inc.		993		19
	Iberiabank Corporation		283		22
	National Bank Holdings Corporation		499		18
	PacWest Bancorp		756		29
	Radian Group, Inc.		948		22
	Selective Insurance Group, Inc.		326		24
	Sterling Bancorp		1,060		23
*	SVB Financial Group		80		18
	Umpqua Holdings Corporation		815		14
	Voya Financial, Inc.		496		27
*	Western Alliance Bancorp		390		17
	WSFS Financial Corporation		416		17
					388
	Real Estate—14.6%
	Acadia Realty Trust		769		21
	American Assets Trust, Inc.		379		18
	American Campus Communities, Inc.		603		28
	Americold Realty Trust		709		23
	Camden Property Trust		247		26
	Douglas Emmett, Inc.		588		23
	EPR Properties		300		22
	Equity LifeStyle Properties, Inc.		179		22
	Healthcare Realty Trust, Inc.		884		28
	Pebblebrook Hotel Trust		652		18
	Terreno Realty Corporation		484		24
					253
	Industrials—13.3%
	Acuity Brands, Inc.		170		24
	AGCO Corporation		287		22
	Brady Corporation		461		23
	Curtiss-Wright Corporation		204		26
	Fortune Brands Home & Security, Inc.		455		26
*	Gardner Denver Holdings, Inc.		645		22
	Jacobs Engineering Group, Inc.		300		25
	Kansas City Southern		177		22
	Simpson Manufacturing Co., Inc.		262		17
	Watsco, Inc.		143		23
					230
	Consumer Discretionary—10.4%
*	Adtalem Global Education, Inc.		490		22
	Carter’s, Inc.		238		23
*	Cavco Industries, Inc.		115		18
	Dana, Inc.		951		19

	Issuer	Shares		Value
	Common Stocks—(continued)
	Consumer Discretionary—(continued)
	Dick’s Sporting Goods, Inc.		543	$	19
	Foot Locker, Inc.		525		22
*	Grand Canyon Education, Inc.		179		21
*	TopBuild Corporation		221		18
	Wolverine World Wide, Inc.		640		18
					180
	Information Technology—10.1%
	Avnet, Inc.		545		25
	Belden, Inc.		321		19
	Booz Allen Hamilton Holding Corporation		450		30
*	Ciena Corporation		337		14
	j2 Global, Inc.		320		28
*	LiveRamp Holdings, Inc.		397		19
	MAXIMUS, Inc.		374		27
*	SolarWinds Corporation		740		14
					176
	Materials—6.3%
	Carpenter Technology Corporation		441		21
	FMC Corporation		222		18
	Minerals Technologies, Inc.		276		15
	PolyOne Corporation		598		19
	Sensient Technologies Corporation		246		18
	Steel Dynamics, Inc.		579		18
					109
	Utilities—5.7%
	Alliant Energy Corporation		453		22
	Atmos Energy Corporation		243		26
	Black Hills Corporation		177		14
	IDACORP, Inc.		194		20
	ONE Gas, Inc.		202		18
					100
	Energy—5.1%
	Murphy Oil Corporation		660		16
	Patterson-UTI Energy, Inc.		1,896		22
	Range Resources Corporation		1,486		11
	Targa Resources Corporation		564		22
*	WPX Energy, Inc.		1,592		18
					89
	Health Care—5.1%
	CONMED Corporation		171		15
	Encompass Health Corporation		347		22
*	Hologic, Inc.		520		25
	PerkinElmer, Inc.		275		26
					88
	Consumer Staples—3.1%
	Ingredion, Inc.		164		13
	J&J Snack Foods Corporation		109		18
	Lamb Weston Holdings, Inc.		363		23
					54

See accompanying Notes to Financial Statements.

22 Semiannual Report June 30, 2019

Small-Mid Cap Value Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Shares		Value
Common Stocks—(continued)
Communication Services—2.9%
Cinemark Holdings, Inc.		531	$	19
Meredith Corporation		230		13
The Interpublic Group of Cos., Inc.		815		18
				50
Total Common Stocks—99.0% (cost $1,514)				1,717
Total Investments—99.0% (cost $1,514)				1,717
Cash and other assets, less liabilities—1.0%				17
Net assets—100.0%			$	1,734

* = Non-income producing security

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 23

	Small Cap Growth Fund
	The Small Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Michael P. Balkin Ward D. Sexton	The William Blair Small Cap Growth Fund (Class N shares) posted an 18.98% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 2000®Growth Index (the “Index”), increased 20.36%. For the year-to-date period, relative underperformance versus the Index was attributable to both stock specific and style dynamics. From a style perspective, and given the Fund’s sensitivity to the valuation of the stocks held, our typical underweight to the most expensive stocks in the benchmark, including within the Biotechnology sector, was a headwind as these groups generally outperformed. From a stock specific perspective, top detractors from the Fund’s relative returns were At Home Group, Inc. (Consumer Discretionary) and Healthcare Services Group, Inc. (Industrials). Shares of home furnishings retailer At Home Group declined on lower-than-expected same store sales growth and a reduced growth outlook. Healthcare Services Group provides outsourced housekeeping, facility maintenance and food services to nursing homes and other care facilities. The stock’s underperformance was most notable during the first quarter, as the company reported revenue that disappointed investors and was primarily attributable to a contract change with one of its food service customers that would dampen revenue, but ultimately lift margins. Other notable underperformers included Inogen, Inc. (Health Care), 2U, Inc. (Information Technology) and Virtu Financial, Inc. (Financials). Conversely, top contributors to performance for the period were Boot Barn Holdings, Inc. (Consumer Discretionary) and Euronet Worldwide, Inc. (Information Technology). Western and work wear retailer Boot Barn outperformed as strong execution against internal initiatives, including the company’s opportunity in private label sales, drove shares higher. Shares of Euronet Worldwide, an electronic payment and transaction processing solutions company, advanced as all three business segments performed well and the company disclosed details about a new cloud-based payments platform which could add to growth over the long term. Other standout performers were Catalent, Inc. (Health Care), Armstrong World Industries, Inc. (Industrials) and OneSpaWorld Holdings, Ltd. (Consumer Discretionary). Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 6 for additional information.

24 Semiannual Report June 30, 2019

Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date		1 Year			3 Year		5 Year		10 Year		Since Inception(a)
Class N		18.98		0.89			19.06		11.20		14.31		—
Class I		19.12		1.14			19.36		11.48		14.61		—
Class R6		—		—			—		—		—		(0.13	)%
Russell 2000® Growth Index		20.36		(0.49	)		14.69		8.63		14.41		0.77

(a) Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller companies involves special risks, including higher volatility and lower liquidity. Smaller capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 2000^®Growth Index is an unmanaged composite of the smallest 2000 stocks of the Russell 3000^®Growth Index.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 25

Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Industrials—24.5%
	Albany International Corporation		116,685	$	9,674
	Argan, Inc.		211,130		8,563
	Armstrong World Industries, Inc.		89,753		8,724
*	Blue Bird Corporation		562,140		11,069
	BWX Technologies, Inc.		267,589		13,941
*	Casella Waste Systems, Inc.		277,170		10,984
	Douglas Dynamics, Inc.		237,817		9,463
	ESCO Technologies, Inc.		89,306		7,378
*	Genesee & Wyoming, Inc.		87,937		8,794
	Healthcare Services Group, Inc.		270,767		8,210
	John Bean Technologies Corporation		80,760		9,782
	Luxfer Holdings plc†		473,515		11,611
*	Mercury Systems, Inc.		143,236		10,077
	Ritchie Bros Auctioneers, Inc.†		286,755		9,526
*	SiteOne Landscape Supply, Inc.		82,468		5,715
	The Brink’s Co.		179,990		14,612
*	Trex Co., Inc.		140,980		10,108
*	Willdan Group, Inc.		138,894		5,174
					173,405
	Health Care—21.5%
*	Amedisys, Inc.		68,780		8,350
*	AxoGen, Inc.		266,270		5,272
*	Cambrex Corporation		223,583		10,466
*	CareDx, Inc.		145,530		5,238
*	Catalent, Inc.		171,438		9,294
*	Codexis, Inc.		353,481		6,515
*	CryoLife, Inc.		291,032		8,710
	Encompass Health Corporation		130,917		8,295
*	Glaukos Corporation		143,543		10,823
*	Halozyme Therapeutics, Inc.		221,050		3,798
*	Hanger, Inc.		463,560		8,877
*	Horizon Therapeutics plc†		453,672		10,915
*	Inspire Medical Systems, Inc.		126,270		7,658
*	LHC Group, Inc.		77,335		9,248
*	Ligand Pharmaceuticals, Inc.		77,179		8,810
*	Penumbra, Inc.		6,423		1,028
*	PolarityTE, Inc.		276,805		1,578
*	Portola Pharmaceuticals, Inc.		357,580		9,701
	Simulations Plus, Inc.		264,780		7,562
*	Veracyte, Inc.		368,880		10,517
					152,655
	Information Technology—18.8%
*	2U, Inc.		190,645		7,176
*	Agilysys, Inc.		643,860		13,824
*	Avalara, Inc.		91,808		6,629
*	Euronet Worldwide, Inc.		76,600		12,887
	j2 Global, Inc.		143,992		12,799
	Littelfuse, Inc.		38,323		6,780
*	LivePerson, Inc.		275,117		7,714
*	MaxLinear, Inc.		422,739		9,909
*	Nice, Ltd.-ADR		56,123		7,689
*	Pure Storage, Inc.		506,746		7,738
*	Qualys, Inc.		80,410		7,002
*	Rogers Corporation		50,574		8,728

	Issuer	Shares		Value
	Common Stocks—(continued)
	Information Technology—(continued)
*	Varonis Systems, Inc.		142,660	$	8,836
*	Verra Mobility Corporation		503,590		6,592
*	WNS Holdings, Ltd.-ADR		153,982		9,116
					133,419
	Consumer Discretionary—12.0%
*	Adtalem Global Education, Inc.		178,963		8,062
*	Aspen Group, Inc.§		724,410		2,753
*	Boot Barn Holdings, Inc.		304,385		10,848
	Dine Brands Global, Inc.		71,170		6,795
*	Etsy, Inc.		64,402		3,952
*	Gentherm, Inc.		150,563		6,298
*	Grand Canyon Education, Inc.		100,943		11,812
*	Hilton Grand Vacations, Inc.		89,804		2,858
*	Laureate Education, Inc.		768,823		12,078
	Lithia Motors, Inc.		73,859		8,773
*	OneSpaWorld Holdings, Ltd.†		705,930		10,942
					85,171
	Financials—6.3%
*	Encore Capital Group, Inc.		297,738		10,084
	FirstCash, Inc.		113,438		11,346
	Glacier Bancorp, Inc.		161,165		6,535
	Home BancShares, Inc.		385,644		7,428
	Virtu Financial, Inc.		420,576		9,160
					44,553
	Communication Services—4.8%
	Cable One, Inc.		11,630		13,619
*	Cars.com, Inc.		238,508		4,703
*	ORBCOMM, Inc.		967,525		7,015
*	QuinStreet, Inc.		538,660		8,538
					33,875
	Consumer Staples—4.1%
*	BJ’s Wholesale Club Holdings, Inc.		275,350		7,269
	Calavo Growers, Inc.		83,151		8,044
*	Darling Ingredients, Inc.		342,880		6,820
*	Primo Water Corporation		568,403		6,991
					29,124
	Real Estate—3.4%
	Colliers International Group, Inc.†		103,274		7,396
	CoreSite Realty Corporation		63,984		7,369
	FirstService Corporation†		94,617		9,076
					23,841
	Energy—1.7%
*	Callon Petroleum Co.		432,183		2,848
	Cameco Corporation†		601,220		6,451
	Centennial Resource Development, Inc.		342,190		2,597
					11,896
	Materials—0.9%
	Orion Engineered Carbons S.A.†		287,092		6,147
	Total Common Stocks—98.0% (cost $578,636)				694,086

See accompanying Notes to Financial Statements.

26 Semiannual Report June 30, 2019

Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Principal
Issuer	Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $11,412, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$11,412	$	11,412
Total Repurchase Agreement—1.6% (cost $11,412)				11,412
Total Investments—99.6% (cost $590,048)				705,498
Cash and other assets, less liabilities—0.4%				2,534
Net assets—100.0%			$	708,032

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

§ = Deemed illiquid pursuant to a Liquidity Risk Management Program approved by the Board of Trustees. This holding represents 0.39% of the Fund’s net assets at June 30, 2019.

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 27

	Small Cap Value Fund
	The Small Cap Value Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Chad M. Kilmer Mark T. Leslie David S. Mitchell	The William Blair Small Cap Value Fund (Class N shares) posted a 16.22% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the Russell 2000®Value Index (the “Index”), increased 13.47%. The Fund’s outperformance relative to the Index was due to the combination of stock selection and style tailwinds primarily due to the strategy’s larger market cap bias and lack of exposure to deeper value stocks. At the sector level, the most significant contributor to relative performance was Information Technology, the best performing sector of the market during the period, due to strong stock selection that was broad-based across most industries. Stock selection within Software, Communication Equipment, IT Services, and Electronic Equipment, Instruments & Components were the most significant contributors to relative performance within the sector. Within Consumer Discretionary, stock selection within Household Durables and Auto Components contributed to the relative outperformance within the sector. The Fund’s relative outperformance within Health Care was due to strong stock selection within Health Care Equipment & Supplies and the lack of exposure to Pharmaceutical and Biotechnology stocks. Real Estate was the most significant detractor from relative performance during the period due to stock selection within Office, Hotel & Resort, and Health Care Real Estate Investment Trusts (“REITs”). Cash was a notable detractor during the period given the strong benchmark return during the first half of the year. Looking specifically at stock selection, the Fund’s largest contributors to relative performance were TopBuild Corporation (Consumer Discretionary), Gardner Denver Holdings, Inc. (Industrials), and Booz Allen Hamilton Holding Corporation (Information Technology). Offsetting these contributors were our investments in Weight Watchers International, Inc. (Consumer Discretionary), Wolverine World Wide, Inc. (Consumer Discretionary), and Range Resources Corporation (Energy). Please refer to the U.S. Value Market Review and Outlook relating to the Fund on page 7 for additional information.

28 Semiannual Report June 30, 2019

Small Cap Value Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		16.22	%		(3.35	)%		7.48	%		4.87	%		12.18	%		—
Class I		16.39			(3.10	)		7.74			5.14			12.46			—
Class R6		—			—			—			—			—			(0.77	)%
Russell 2000®Value Index		13.47			(6.24	)		9.81			5.39			12.40			(1.54	)

(a)  Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller companies involves special risks, including higher volatility and lower liquidity. Smaller capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Russell 2000^®Value Index consists of small-capitalization companies with below average price-to-book ratios and forecasted growth rates.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 29

Small Cap Value Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Financials—26.3%
	Banc of California, Inc.		244,137	$	3,411
	Banner Corporation		96,290		5,214
	Boston Private Financial Holdings, Inc.		310,693		3,750
	CNO Financial Group, Inc.		252,519		4,212
	CVB Financial Corporation		161,926		3,405
	FNB Corporation		447,308		5,265
	Glacier Bancorp, Inc.		83,634		3,391
	Hancock Whitney Corporation		154,672		6,196
	Hanover Insurance Group, Inc.		44,271		5,680
	Home BancShares, Inc.		318,473		6,134
	Horace Mann Educators Corporation		86,460		3,483
	Iberiabank Corporation		72,295		5,484
	National Bank Holdings Corporation		148,364		5,386
	OceanFirst Financial Corporation		187,682		4,664
	PacWest Bancorp		121,564		4,720
	Radian Group, Inc.		293,198		6,700
	Renasant Corporation		144,672		5,199
	Sandy Spring Bancorp, Inc.		151,817		5,295
*	Seacoast Banking Corporation of Florida		199,945		5,087
	Selective Insurance Group, Inc.		90,995		6,815
	Sterling Bancorp		278,195		5,920
	Umpqua Holdings Corporation		244,942		4,064
*	Western Alliance Bancorp		107,120		4,790
	WSFS Financial Corporation		117,872		4,868
					119,133
	Industrials—12.5%
	Acuity Brands, Inc.		41,583		5,735
	Brady Corporation		137,594		6,786
*	Continental Building Products, Inc.		198,888		5,285
	Curtiss-Wright Corporation		55,480		7,053
	ESCO Technologies, Inc.		69,792		5,766
	Kennametal, Inc.		131,980		4,882
	Matson, Inc.		122,461		4,758
	Simpson Manufacturing Co., Inc.		78,861		5,241
	Watsco, Inc.		36,950		6,042
	Watts Water Technologies, Inc.		55,878		5,207
					56,755
	Real Estate—11.2%
	Acadia Realty Trust		199,398		5,458
	Agree Realty Corporation		50,952		3,264
	American Assets Trust, Inc.		97,651		4,601
	Americold Realty Trust		182,245		5,908
	Columbia Property Trust, Inc.		157,187		3,260
	Equity Commonwealth		100,941		3,283
	Healthcare Realty Trust, Inc.		227,721		7,132
	Highwoods Properties, Inc.		142,349		5,879
	Pebblebrook Hotel Trust		202,311		5,701
	Terreno Realty Corporation		129,349		6,343
					50,829

	Issuer	Shares		Value
	Common Stocks—(continued)
	Consumer Discretionary—9.9%
	Abercrombie & Fitch Co.		239,506	$	3,842
*	Adtalem Global Education, Inc.		124,547		5,611
	Carter’s, Inc.		58,001		5,657
*	Cavco Industries, Inc.		29,728		4,683
	Dana, Inc.		258,777		5,160
	Dave & Buster’s Entertainment, Inc.		78,787		3,188
	Dick’s Sporting Goods, Inc.		131,009		4,537
	Foot Locker, Inc.		108,315		4,541
*	TopBuild Corporation		47,126		3,900
	Wolverine World Wide, Inc.		137,691		3,792
					44,911
	Information Technology—9.5%
	Avnet, Inc.		120,681		5,463
	Belden, Inc.		91,071		5,425
*	Inphi Corporation		81,908		4,104
	j2 Global, Inc.		69,487		6,177
*	LiveRamp Holdings, Inc.		88,329		4,282
	MAXIMUS, Inc.		64,192		4,656
*	Semtech Corporation		83,691		4,021
*	SolarWinds Corporation		187,925		3,447
*	Viavi Solutions, Inc.		420,447		5,588
					43,163
	Energy—6.5%
	Archrock, Inc.		460,262		4,879
*	Callon Petroleum Co.		771,222		5,082
*	Helix Energy Solutions Group, Inc.		437,968		3,780
*	Newpark Resources, Inc.		438,363		3,253
*	PDC Energy, Inc.		134,883		4,864
	Range Resources Corporation		446,502		3,116
	Solaris Oilfield Infrastructure, Inc.		236,178		3,538
*	Talos Energy, Inc.		31,302		753
					29,265
	Health Care—6.0%
	CONMED Corporation		97,651		8,356
	Encompass Health Corporation		109,209		6,920
*	Integer Holdings Corporation		92,999		7,804
*	Magellan Health, Inc.		53,601		3,979
					27,059
	Utilities—6.0%
	Black Hills Corporation		50,822		3,973
	Chesapeake Utilities Corporation		33,542		3,187
	IDACORP, Inc.		45,933		4,613
	ONE Gas, Inc.		61,705		5,572
	PNM Resources, Inc.		99,765		5,079
	South Jersey Industries, Inc.		136,003		4,587
					27,011

See accompanying Notes to Financial Statements.

30 Semiannual Report June 30, 2019

Small Cap Value Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares or Principal Amount		Value
	Common Stocks—(continued)
	Materials—4.5%
	Carpenter Technology Corporation		94,844	$	4,551
	Minerals Technologies, Inc.		62,589		3,349
	PolyOne Corporation		109,929		3,451
	Sensient Technologies Corporation		66,197		4,864
	Silgan Holdings, Inc.		126,842		3,881
					20,096
	Communication Services—2.7%
	Cinemark Holdings, Inc.		114,583		4,136
*	IMAX Corporation†		131,135		2,649
	Meredith Corporation		98,939		5,448
					12,233
	Consumer Staples—2.6%
*	Darling Ingredients, Inc.		265,436		5,279
	J&J Snack Foods Corporation		40,360		6,496
					11,775
	Total Common Stocks—97.7% (cost $351,482)				442,230
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $6,411, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$6,410		6,410
	Total Repurchase Agreement—1.4% (cost $6,410)				6,410
	Total Investments—99.1% (cost $357,892)				448,640
	Cash and other assets, less liabilities—0.9%				4,297
	Net assets—100.0%			$	452,937

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 31

Global Markets Review and Outlook

Global equities posted strong results for the first half of 2019 despite signals of decelerating global growth and mounting uncertainty surrounding trade relations between the U.S. and China. Gains across most markets were primarily driven by the more accommodative tone out of major central banks. From a geopolitical perspective, the prospect of a trade deal between the U.S. and China, which fueled equity markets to start the year, quickly soured in the month of May following news that the U.S. would increase tariffs from 10% to 25% on nearly half the goods purchased from China (roughly $200 billion in U.S. Dollar terms). Despite the unexpected volatility in May, equities rebounded in June to close out a strong first six months of the year with the MSCI ACWI Investable Market Index (“IMI”) up 16.07% year-to-date.

U.S. equities rallied in the first half of 2019 (+18.42% as measured by the MSCI USA IMI) after the large selloff in the fourth quarter of 2018. Growth in the U.S. remained solid but started to decelerate off of last year’s previous highs. The Federal Reserve’s acknowledgment of slower economic growth and dovish stance on interest rates helped ease investor sentiment and boosted returns across sectors, especially cyclically-oriented sectors such as Information Technology, Industrials and Consumer Discretionary.

European equities also advanced despite signs of significant deceleration in manufacturing growth. Specifically, purchasing manager surveys continued to point to deceleration in the pace of industrial orders growth and subsequent industrial production growth in the Euro Area. This was especially evident in Germany where manufacturing growth has been shrinking and business sentiment has weakened over the past year. As European sovereign 10-year bond yields hit record lows in June, the European Central Bank announced that further monetary stimulus to boost inflation was ready if needed. The MSCI Europe ex U.K. IMI advanced 5.64% for the second quarter and 16.74% year-to-date in U.S. dollar terms.

Ambiguity surrounding Brexit continued to weigh on the economic conditions within the U.K. Equities felt some relief to start the year after the U.K. was granted two extensions from the European Union to delay the Brexit process past the March 29, 2019 deadline and then against past the April 12, 2019 deadline to the current October 31, 2010 deadline. But political woes returned following the failed final bid to get a Brexit deal through parliament and the subsequent resignation of Prime Minister Theresa May. While the Conservative Party began the process of selecting its new leader, who will also become Prime Minister, political uncertainty drove Sterling weakness amid increased expectations of a disorderly Brexit. The MSCI U.K. IMI advanced modestly for the second quarter (+0.74%), but was up 13.16% year-to-date in US dollar terms.

Equity performance across Emerging Market countries was mixed year-to-date. China equities declined 4.11% in the second quarter amid the trade war re-escalation and lower expectations regarding the level of government stimulus measures. Despite this correction, Chinese shares (including Hong Kong and New York-listed companies) were up 12.73% for the six-month period, while China’s mainland-listed securities (A-shares) advanced 28.28% (as measured by the MSCI China A Onshore Index). Higher crude prices contributed to strong equity market gains across oil exporting countries such as Russia (+30.70%) and Brazil (+16.39%), but negatively impacted oil importing countries such as India (+6.43%) and Indonesia (+6.88%) year-to-date (as measured by the MSCI Emerging Markets IMI).

The global growth environment appears to be stabilizing after a period of deceleration in economic activity over the past year. Among the higher frequency data that we monitor, we have been encouraged by recent stabilization in the orders minus inventories component of the Manufacturing Purchasing Managers’ Indexes (“PMIs”) in the U.S., Euro Area, U.K. and Japan, signaling a rebound in industrial production volumes.

Looking forward to the second half of the year, we see geopolitical risks to economic activity abating: U.S.-China trade talks are back on, European Parliamentary elections are behind us, and the recently announced key European appointments (European Central Bank and European Commission presidents) suggest a better policy mix going forward.

U.S.-China tariff threats moderated toward the end of the period, which was particularly important as the escalation in hostilities and uncertainty about a potential trade deal weighed on industrial activity and order flows in the first half of 2019. At the same time, we saw signs of a bottoming in activity even before the announced truce in Osaka-notably that sales of semiconductors had troughed. This is an increasingly valuable indicator of near-term economic momentum. While the industry has consolidated and matured, semiconductors are used increasingly widely in almost all areas of industrial manufacturing and production.

Bond market investors are suggesting a different verdict on the global economy, however. The dichotomy of views expressed by equities and fixed income investors is best encapsulated by the decoupling of economic growth (equities) and inflation (bonds). Specifically, U.S. inflation continues to edge lower (1.6% year-over-year), even as the U.S. economy enters its tenth year of expansion. The situation is broadly repeated across many developed economies. It is little surprise then that the U.S. Federal Reserve feels compelled to lower rates.

32 Semiannual Report June 30, 2019

Global Markets Review and Outlook (continued)

From a corporate earnings perspective, net income growth appears to be bottoming in the Euro Area, the U.K., Japan and China after an 18 month period of steady deceleration. U.S. earnings growth has recently stabilized at 19% after weakening from 27% in December 2018, although consensus growth estimates for the next twelve months are significantly lower at 6%. This discrepancy in actual versus future U.S. growth expectations starkly contrasts with non-U.S. markets, where forward expectations are more in line with current growth rates, reflecting the shrinking economic growth wedge that has favored the U.S.

Equity valuations have stabilized and are broadly similar across different geographic regions following the sizable de-rating that occurred during the fourth quarter 2018 market selloff. Price/Earnings multiples in the U.S. and Euro Area are roughly in line with their respective ten year averages, while China is trading modestly below its ten year average multiple.

Although positioning changes by sector and geography varied across our strategies during the first half of the year, there were some broadly consistent themes reflecting the market environment and company fundamentals. From a sector perspective, Information Technology and Industrials weightings were generally higher due to our active repositioning into relatively attractive areas like software, payments and machinery. From a country perspective, exposures to China and India were incrementally increased across most strategies, while Japan weightings were reduced in our global/non-U.S. strategies.

June 30, 2019 William Blair Funds 33

	Global Leaders Fund
	The Global Leaders Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Andrew G. Flynn Kenneth J. McAtamney	The William Blair Global Leaders Fund (Class N shares) posted a 20.66% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI All Country World IMI Index (net) (the “Index”), increased 16.07%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Consumer Staples, Health Care and Financials sectors were the most significant sources of the Fund’s relative return. Within Consumer Staples, The Estee Lauder Cos., Inc. aided relative performance as results came in stronger than expected driven by strength in Asia, travel retail, and skincare. Estee Lauder is a leading global prestige cosmetics company with more than 30,000 points of distribution in over 150 countries across various channels, including department stores, specialty cosmetics stores, travel retail, and online. We expect the company to benefit from the rapid growth of newly acquired brands, the continued expansion in the specialty retail and online channels, and strong growth from China and travel retail. Within Healthcare, Zoetis, Inc., the largest global provider of animal healthcare products, was an additional source of outperformance as the company reported another solid quarter by beating estimates. Zoetis is a unique company with strong secular growth drivers such as population growth and a rising middle class with increasing per capita income in developed markets. In addition, the animal healthcare industry compares favorably to human health care as there are no patent cliffs threatening sales, the pricing environment is benign, and R&D productivity is higher. Within Financials, AIA Group, Ltd. bolstered relative results. AIA is a leading provider of life insurance throughout Asia. The company continues to benefit from strong demand for its products due to its dominant brand and competitive advantages in distribution and product innovation, coupled with rising affluence and insurance penetration within Asia. Furthermore, China announced plans to further open up its insurance markets to foreign competition, boosting sentiment in the sector. Partially offsetting these effects was an underweight allocation to the Consumer Staples sector, coupled with below average stock selection within the Materials sector. Within Materials, Nissan Chemical Corp. hindered relative returns due to results that were weaker than consensus, mostly due to slower smartphone sales. Nissan Chemical is an innovative Japanese producer of niche chemicals for the electronics, agriculture, and pharmaceutical industries. It has a leading position in its core products and a track record of innovation supported by its commitment to high levels of research and development. While Nissan Chemical’s business model remains unchanged, we trimmed the position to reflect uncertainty around the company’s near-term conditions. Victrex plc, a chemicals company that is the world’s leading producer of a niche, high performance plastic, also underperformed in the period due to weak demand from automotive and electronic end-markets. Over the long-term, we believe Victrex will deliver above-average growth rates relative to its chemical peer group due to increasing demand for high performance plastics across a large and growing number of end markets. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

34 Semiannual Report June 30, 2019

Global Leaders Fund

Performance Highlights (Unaudited)

 

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception
Class N		20.66	%		4.14	%		13.86	%		8.11	%		11.89	%		—
Class I		20.92			4.44			14.19			8.43			12.19			—
MSCI ACW IMI (net)		16.07			4.56			11.42			6.03			10.32			—
Class R6(a)		20.92			4.44			14.26			8.48			—			10.37	%
MSCI ACW IMI (net)(a)		16.07			4.56			11.42			6.03			—			8.97

(a) Since inception is for the period from December 19, 2012 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) All Country World (ACW) Investable Market Index (IMI) (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market of developed and emerging markets. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 35

Global Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Western Hemisphere—52.7%
	Canada—1.6%
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		69,884	$	3,339
	United States—51.1%
*	ABIOMED, Inc. (Health care equipment & supplies)		5,791		1,508
*	Adobe, Inc. (Software)		13,187		3,886
*	Align Technology, Inc. (Health care equipment & supplies)		3,869		1,059
*	Alphabet, Inc. Class “A” (Interactive Media & Services)		4,982		5,394
*	Amazon.com, Inc. (Internet & direct marketing retail)		3,268		6,188
	BlackRock, Inc. (Capital markets)		7,869		3,693
*	CoStar Group, Inc. (Professional services)		3,833		2,124
	Domino’s Pizza, Inc. (Hotels, restaurants & leisure)		9,357		2,604
*	Facebook, Inc. Class “A” (Interactive Media & Services)		23,267		4,491
	Fifth Third Bancorp (Banks)		70,390		1,964
*	Guidewire Software, Inc. (Software)		16,472		1,670
*	IDEXX Laboratories, Inc. (Health care equipment & supplies)		8,945		2,463
*	Illumina, Inc. (Life sciences tools & services)		4,339		1,597
	Intercontinental Exchange, Inc. (Capital markets)		41,800		3,592
*	Intuitive Surgical, Inc. (Health care equipment & supplies)		4,059		2,129
	JPMorgan Chase & Co. (Banks)		33,138		3,705
	Mastercard, Inc. Class “A” (IT services)		20,580		5,444
	NextEra Energy, Inc. (Electric utilities)		14,847		3,042
*	PayPal Holdings, Inc. (IT services)		31,842		3,645
	Prologis, Inc. (Equity REIT)		27,361		2,192
	Roper Technologies, Inc. (Industrial conglomerates)		11,463		4,198
*	salesforce.com, Inc. (Software)		25,835		3,920
	Southwest Airlines Co. (Airlines)		20,620		1,047
	The Boeing Co. (Aerospace & defense)		8,014		2,917
	The Estee Lauder Cos., Inc. Class “A” (Personal products)		20,285		3,714
	The Goldman Sachs Group, Inc. (Capital markets)		10,503		2,149
	Thermo Fisher Scientific, Inc. (Life sciences tools & services)		12,510		3,674
*	Ulta Salon Cosmetics & Fragrance, Inc. (Specialty retail)		8,382		2,908
	Union Pacific Corporation (Road & rail)		25,144		4,252
	UnitedHealth Group, Inc. (Health care providers & services)		18,469		4,507
	Vail Resorts, Inc. (Hotels, restaurants & leisure)		11,226		2,505
*	Veeva Systems, Inc. Class “A” (Health care technology)		8,688		1,408
*	Worldpay, Inc. Class “A” (IT services)		32,188		3,945
	Zoetis, Inc. (Pharmaceuticals)		30,582		3,471
					107,005

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe—17.6%
	Denmark—2.5%
	Chr Hansen Holding A/S (Chemicals)		25,609	$	2,405
	DSV A/S (Road & rail)		28,058		2,755
					5,160
	France—2.1%
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		10,232		4,355
	Germany—2.5%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		138,275		2,445
	MTU Aero Engines AG (Aerospace & defense)		11,512		2,742
					5,187
	Ireland—2.0%
	Allegion plc (Building products)†		18,893		2,089
	Aptiv plc (Auto components)†		27,092		2,190
					4,279
	Netherlands—1.3%
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		86,568		2,826
	Sweden—4.1%
	Atlas Copco AB Class “A” (Machinery)		115,318		3,686
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		66,806		3,709
	Indutrade AB (Trading companies & distributors)		34,507		1,103
					8,498
	Switzerland—3.1%
*	Lonza Group AG (Life sciences tools & services)		9,431		3,182
	Partners Group Holding AG (Capital markets)		4,148		3,259
					6,441
	Emerging Asia—9.7%
	China—5.7%
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		28,272		4,791
	Huazhu Group, Ltd.—ADR (Hotels, restaurants & leisure)		36,291		1,315
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		120,000		1,650
	Tencent Holdings, Ltd. (Interactive Media & Services)		94,000		4,243
					11,999
	India—1.6%
	HDFC Bank, Ltd.—ADR (Banks)		26,241		3,412
	Taiwan—2.4%
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		126,833		4,968

See accompanying Notes to Financial Statements.

36 Semiannual Report June 30, 2019

Global Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares			Value
	Common Stocks—(continued)
	Asia—8.1%
	Australia—4.6%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		96,919		$	2,090
	CSL, Ltd. (Biotechnology)		28,899			4,362
	Macquarie Group, Ltd. (Capital markets)		35,714			3,144
						9,596
	Hong Kong—3.5%
	AIA Group, Ltd. (Insurance)		415,400			4,480
	Galaxy Entertainment Group, Ltd. (Hotels, restaurants & leisure)		415,000			2,797
						7,277
	Japan—6.5%
	Daikin Industries, Ltd. (Building products)		27,700			3,614
	Keyence Corporation (Electronic equipment, instruments & components)		5,700			3,496
	M3, Inc. (Health care technology)		9,300			170
	MISUMI Group, Inc. (Machinery)		34,400			862
	Nihon M&A Center, Inc. (Professional services)		74,900			1,795
	Nissan Chemical Corp. (Chemicals)		19,200			865
	SMC Corporation (Machinery)		3,500			1,304
	ZOZO Inc. (Internet & direct marketing retail)		82,300			1,541
						13,647
	United Kingdom—3.6%
	Burford Capital, Ltd. (Capital markets)		68,704			1,352
	Compass Group plc (Hotels, restaurants & leisure)		148,460			3,558
	Fevertree Drinks plc (Beverages)		33,351	��		982
	Victrex plc (Chemicals)		64,172			1,763
						7,655
	Emerging Latin America—0.7%
	Argentina—0.7%
*	Globant S.A. (Software)†		14,216			1,437
	Total Common Stocks—98.9% (cost $152,185)					207,081

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $4,765, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$4,765	$	4,765
Total Repurchase Agreement—2.3% (cost $4,765)				4,765
Total Investments—101.2% (cost $156,950)				211,846
Liabilities, plus cash and other assets—(1.2)%				(2,560	)
Net assets—100.0%			$	209,286

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

† = U.S. listed foreign security

* = Non-income producing security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Information Technology	18.5	%
Consumer Discretionary	18.5	%
Industrials	16.7	%
Financials	16.5	%
Health Care	14.3	%
Communication Services	6.8	%
Materials	2.4	%
Consumer Staples	2.3	%
Utilities	1.5	%
Energy	1.4	%
Real Estate	1.1	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

U.S. Dollar	63.0	%
Japanese Yen	6.6	%
Hong Kong Dollar	6.4	%
Euro	6.0	%
Australian Dollar	4.6	%
Swedish Krona	4.1	%
British Pound Sterling	3.7	%
Swiss Franc	3.1	%
Danish Krone	2.5	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 37

	International Leaders Fund
	The International Leaders Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Simon Fennell Kenneth J. McAtamney	The William Blair International Leaders Fund (Class N shares) posted a 20.58% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI Index (net) (the “Index”), increased 13.33%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Financials, Materials and Industrials sectors were the most significant contributors to the Fund’s relative return. Within Financials, AIA Group, Ltd. helped relative returns as the company continued to generate strong double-digit VNB (value of new business) growth, a key financial metric. AIA is a leading provider of life insurance throughout Asia. The company continues to benefit from strong demand for its products due to its dominant brand position and competitive advantages in distribution and product innovation, coupled with rising affluence and insurance penetration within Asia. Furthermore, China announced plans to further open up its insurance markets to foreign competition, booting sentiment in the sector. Sika AG, a construction materials company within the Materials sector, was an additional source of outperformance. Sika boasts a diversified set of value-added products that simplify construction projects, lower completion time, and enhance building efficiency and sustainability. Increasing urbanization along with a heightened focus on sustainability provides Sika with a favorable structural backdrop and a market more receptive to innovation. Competitive dynamics are currently positive as well, as Sika’s two main competitors, BASF SE and W.R. Grace & Co., are facing challenges, allowing Sika a unique opportunity to gain market share both organically and via M&A. Within the Industrials sector, Airbus SE boosted relative performance. Product transitions to the next generation of aircrafts that have pressured earnings and cash flows at the company over the last several years have peaked, leaving the company in a favorable position where investment is moderating and profitability is poised to improve. Partially offsetting these effects were underweight allocations to the Materials and Consumer Staples sectors, which outperformed the Index during the period, coupled with below average stock selection within the Communication Services sector. Within Communication Services, Rogers Communications, Inc. and Tencent Holdings, Ltd. detracted from relative performance. Rogers Communications, an industry leader with high quality customers and a favorable spectrum position in Canada, reported soft wireless subscription growth during the period, leading us to trim the position. Tencent, the Chinese online gaming and social network giant, reported weaker-than-expected advertising revenue growth during the period. While results were disappointing, the economic backdrop was difficult and the company still has very high demand for the limited advertising slots it is making available to its engaged social media user base. We believe Tencent can continue to manage advertising growth at a relatively high level while delivering relevant advertisements to users, supporting our investment thesis. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

38 Semiannual Report June 30, 2019

International Leaders Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		20.58	%		4.18	%		11.77	%		6.72	%		9.14	%
Class I(a)		20.66			4.44			12.07			6.98			9.41
MSCI ACW Ex-U.S. IMI (net)(a)		13.33			0.26			9.17			2.25			5.96
Class R6(b)		20.75			4.53			12.19			7.08			9.46
MSCI ACW Ex-U.S. IMI (net)(b)		13.33			0.26			9.17			2.25			5.56

(a)	Since inception is for the period from August 16, 2012 (Commencement of Operations) to June 30, 2019.
(b)	Since inception is for the period from November 2, 2012 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. From time to time the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) All Country World (ACW) Ex-U.S. Investable Market Index (IMI) (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed and emerging markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 39

International Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe, Mid-East—43.0%
	Denmark—4.2%
	Coloplast A/S Class “B” (Health care equipment & supplies)		83,860	$	9,477
	DSV A/S (Road & rail)		44,293		4,349
	Orsted A/S (Electric utilities)		104,312		9,020
					22,846
	Finland—0.4%
	Neste Oyj (Oil, gas & consumable fuels)		73,231		2,485
	France—9.4%
	Airbus SE (Aerospace & defense)		94,486		13,395
	Capgemini SE (IT services)		82,713		10,285
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		34,286		14,593
	Safran S.A. (Aerospace & defense)		89,469		13,108
					51,381
	Germany—4.9%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		424,292		7,502
	Rational AG (Machinery)		8,791		6,053
	SAP SE (Software)		94,423		12,966
					26,521
	Ireland—1.8%
	Kingspan Group plc (Building products)		179,200		9,732
	Israel—1.6%
*	Check Point Software Technologies, Ltd. (Software)†		74,722		8,639
	Italy—0.6%
	Ferrari N.V. (Automobiles)		19,307		3,135
	Luxembourg—0.8%
	Tenaris S.A. (Energy equipment & services)		316,710		4,145
	Netherlands—4.9%
*	Adyen N.V. (IT services)		7,020		5,417
	Koninklijke Philips N.V. (Health care equipment & supplies)		266,090		11,554
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		296,306		9,673
					26,644
	Spain—3.7%
	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		245,583		9,805
	Amadeus IT Group S.A. (IT services)		134,293		10,637
					20,442
	Sweden—3.3%
	Atlas Copco AB Class “A” (Machinery)		314,949		10,066
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		148,654		8,254
					18,320

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Switzerland—7.4%
*	Lonza Group AG (Life sciences tools & services)		37,003	$	12,486
	Partners Group Holding AG (Capital markets)		11,797		9,269
	Sika AG (Chemicals)		47,290		8,070
*	Temenos AG (Software)		59,007		10,557
					40,382
	United Kingdom—13.6%
	Abcam plc (Biotechnology)		133,853		2,505
	Compass Group plc (Hotels, restaurants & leisure)		443,907		10,638
	Diageo plc (Beverages)		257,349		11,059
	Experian plc (Professional services)		384,132		11,630
*	Ferguson plc (Trading companies & distributors)		99,930		7,107
	London Stock Exchange Group plc (Capital markets)		115,112		8,020
	RELX plc (Professional services)		446,282		10,822
	Segro plc (Equity REIT)		853,098		7,911
	St James’s Place plc (Capital markets)		328,153		4,576
					74,268
	Emerging Asia—12.5%
	China—8.5%
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		87,315		14,795
	China Merchants Bank Co., Ltd. Class “H” (Banks)		2,246,500		11,201
	NetEase, Inc.-ADR (Entertainment)		31,153		7,968
	Tencent Holdings, Ltd. (Interactive Media & Services)		275,000		12,413
					46,377
	India—1.6%
	Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		277,223		8,813
	Taiwan—2.4%
	Taiwan Semiconductor Manufacturing Co., Ltd. (Semiconductors & semiconductor equipment)		1,692,000		13,020
	Asia—9.7%
	Australia—5.1%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		274,593		5,922
	CSL, Ltd. (Biotechnology)		72,903		11,004
	Macquarie Group, Ltd. (Capital markets)		123,695		10,889
					27,815

See accompanying Notes to Financial Statements.

40 Semiannual Report June 30, 2019

International Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Asia—(continued)
	Hong Kong—4.6%
	AIA Group, Ltd. (Insurance)		1,670,800	$	18,020
	Galaxy Entertainment Group, Ltd. (Hotels, restaurants & leisure)		1,050,000		7,077
					25,097
	Canada—9.3%
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		240,836		11,507
	Canadian National Railway Co. (Road & rail)		151,816		14,051
	Dollarama, Inc. (Multiline retail)		183,201		6,445
	Rogers Communications, Inc. Class “B” (Wireless telecommunication services)		128,845		6,897
	The Toronto-Dominion Bank (Banks)		204,127		11,928
					50,828
	Japan—8.0%
	Daikin Industries, Ltd. (Building products)		60,700	$	7,919
	Keyence Corporation (Electronic equipment, instruments & components)		22,200		13,617
	Nitori Holdings Co., Ltd. (Specialty retail)		50,600		6,702
	Shiseido Co., Ltd. (Personal products)		131,000		9,867
	SMC Corporation (Machinery)		15,700		5,849
					43,954
	Emerging Europe, Mid-East, Africa—0.8%
	South Africa—0.8%
	Bid Corporation, Ltd. (Food & staples retailing)		190,867		4,160
	Total Common Stocks—96.9% (cost $427,877)				529,004
	Rights
	Spain—0.1%
*	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		242,788		381
	Total Rights—0.1% (cost $400)				381

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $17,338, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26	$	17,337	$	17,337
Total Repurchase Agreement—3.2% (cost $17,337)				17,337
Total Investments—100.2% (cost $445,614)				546,722
Liabilities, plus cash and other assets—(0.2)%				(1,102	)
Net assets—100.0%			$	545,620

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	23.4	%
Information Technology	19.1	%
Financials	17.8	%
Consumer Discretionary	13.1	%
Health Care	8.9	%
Communication Services	5.2	%
Consumer Staples	4.7	%
Energy	3.1	%
Utilities	1.7	%
Materials	1.5	%
Real Estate	1.5	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	27.4	%
British Pound Sterling	14.0	%
Hong Kong Dollar	9.2	%
Japanese Yen	8.3	%
U.S. Dollar	8.1	%
Swiss Franc	7.6	%
Canadian Dollar	7.4	%
Australian Dollar	5.2	%
Danish Krone	4.3	%
Swedish Krona	3.5	%
New Taiwan Dollar	2.5	%
Indian Rupee	1.7	%
All Other Currencies	0.8	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 41

	International Developed Plus Fund (In Liquidation)
	The International Developed Plus Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
David Merjan John C. Murphy	The William Blair International Developed Plus Fund (Class N shares) posted a 21.02% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI World ex-U.S. Index (net) (the “Index”), increased 14.64%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Financials and Industrials sectors were the most notable contributors to the Fund’s relative return. Within the Financials sector, Partners Group Holding AG and AIA Group Ltd. enhanced relative performance. Switzerland-based asset manager Partners Group’s share price was supported by solid fiscal year 2018 results, including base management fees, EBITDA and dividend payouts that were above consensus estimates. Client demand remains strong for private market investments and Partners Group remains selective on asset purchases given structurally high valuations. AIA Group is a leading pan-Asian insurer. The company continues to benefit from strong demand for its products due to its dominant brand position and competitive advantages in distribution and product innovation, coupled with rising affluence and insurance penetration within Asia. Furthermore, China announced plans to further open up its insurance markets to foreign competition, booting sentiment in the sector. France aircraft manufacturer Airbus SE led performance within the Industrials sector. Product transitions to the next generation of aircrafts that have pressured earnings and cash flows at the company over the last several years have peaked, leaving Airbus in a favorable position where investment is moderating and profitability is poised to improve. Partially offsetting these effects were underweight allocations to Europe and Japan, which outperformed the Index during the period, coupled with below average stock selection within the Communication Services and Energy sectors. Within the Communications Services sector, Canadian telecom company Rogers Communications, Inc. detracted from performance, as the share price was hampered by weaker wireless subscriber growth. While still generally healthy, the wireless market outlook is more moderated in 2019 versus the prior two years where we saw solid subscriber growth and strong pricing trends. Returns from Rogers’ wireless segment in the first quarter of 2019, coupled with some market share loss, underscored this reality. We sold the position as a result. Within Energy, Canada-based oil and gas company Enerplus Corporation detracted from performance, due to weaker oil prices and mixed financial results. Enerplus’s overall production declined 9.5% sequentially as the company lowered operating activity following weaker oil pricing. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

42 Semiannual Report June 30, 2019

International Developed Plus Fund (In Liquidation)

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date		1 Year		3 Year		5 Year		10 Year
Class N	21.02	%	3.51	%	8.15	%	3.14	%	7.17	%
Class I	21.16		3.74		8.42		3.40		7.43
MSCI World Ex-U.S. Index (net)	14.64		1.29		9.01		2.04		6.75

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. From time to time the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) World Ex-U.S. Index (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 43

International Developed Plus Fund (In Liquidation)

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe—58.2%
	Denmark—2.7%
	DSV A/S (Road & rail)		4,368	$	429
	France—13.4%
	Airbus SE (Aerospace & defense)		4,725		670
	Capgemini SE (IT services)		3,862		480
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		1,198		510
	Safran S.A. (Aerospace & defense)		3,368		494
					2,154
	Germany—13.1%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		21,914		387
	MTU Aero Engines AG (Aerospace & defense)		3,483		830
*	QIAGEN N.V. (Life sciences tools & services)†		6,956		282
	SAP SE (Software)		4,355		598
					2,097
	Ireland—6.3%
	Accenture plc Class “A” (IT services)†		2,169		401
	Kerry Group plc Class “A” (Food products)		5,060		604
					1,005
	Netherlands—4.8%
*	Adyen N.V. (IT services)		210		162
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		18,420		601
					763
	Sweden—2.2%
	Atlas Copco AB Class “A” (Machinery)		11,303		361
	Switzerland—15.7%
*	Alcon, Inc. (Health care equipment & supplies)		6,197		383
	Novartis AG (Pharmaceuticals)		5,196		475
	Partners Group Holding AG (Capital markets)		1,057		830
	Straumann Holding AG (Health care equipment & supplies)		547		483
	Tecan Group AG (Life sciences tools & services)		1,322		343
					2,514
	United Kingdom—26.0%
	AstraZeneca plc (Pharmaceuticals)		8,275		677
	Compass Group plc (Hotels, restaurants & leisure)		44,198		1,059
	Diageo plc (Beverages)		24,747		1,063
	Halma plc (Electronic equipment, instruments & components)		18,303		470
	Legal & General Group plc (Insurance)		88,671		303
	Prudential plc (Insurance)		27,059		590
					4,162

	Issuer	Shares		Value
	Common Stocks—(continued)
	Japan—15.0%
	Daikin Industries, Ltd. (Building products)		4,118	$	537
	Hoya Corporation (Health care equipment & supplies)		5,800		444
	Keyence Corporation (Electronic equipment, instruments & components)		1,100		675
	Nihon M&A Center, Inc. (Professional services)		11,380		273
	Shiseido Co., Ltd. (Personal products)		6,300		474
					2,403
	Canada—14.2%
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		9,850		471
	Canadian National Railway Co. (Road & rail)†		10,565		977
	The Toronto-Dominion Bank (Banks)†		14,213		829
					2,277
	Asia—12.4%
	Australia—6.6%
	CSL, Ltd. (Biotechnology)		3,576		540
	Goodman Group (Equity REIT)		49,863		526
					1,066
	Hong Kong—5.8%
	AIA Group, Ltd. (Insurance)		85,586		923
	Emerging Asia—10.8%
	China—3.2%
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		3,063		519
	India—3.8%
	HDFC Bank, Ltd.-ADR (Banks)		4,636		603
	Taiwan—3.8%
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		15,423		604
	Emerging Latin America—2.0%
	Peru—2.0%
	Credicorp, Ltd. (Banks)†		1,405		322
	Total Common Stocks—138.6% (cost $18,183)				22,202

See accompanying Notes to Financial Statements.

44 Semiannual Report June 30, 2019

International Developed Plus Fund (In Liquidation)

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $2,046, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$2,046	$	2,046
Total Repurchase Agreement—12.8% (cost $2,046)				2,046
Total Investments—151.4% (cost $20,229)				24,248
Liabilities, plus cash and other assets—(51.4)%				(8,237	)
Net assets—100.0%			$	16,011

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Financials	21.9	%
Industrials	20.7	%
Information Technology	17.0	%
Health Care	16.3	%
Consumer Staples	9.6	%
Consumer Discretionary	9.4	%
Energy	2.7	%
Real Estate	2.4	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	24.0	%
U.S. Dollar	22.6	%
British Pound Sterling	18.8	%
Swiss Franc	11.3	%
Japanese Yen	10.8	%
Australian Dollar	4.8	%
Hong Kong Dollar	4.2	%
Danish Krone	1.9	%
Swedish Krona	1.6	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 45

	Institutional International Developed Plus Fund (In Liquidation)
	The Institutional International Developed Plus Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
David Merjan John C. Murphy	The William Blair Institutional International Developed Plus Fund posted a 20.69% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI World ex-U.S. Index (net) (the “Index”), increased 14.64%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Financials and Industrials sectors were the most notable contributors to the Fund’s relative return. Within the Financials sector, Partners Group Holding AG and AIA Group Ltd. enhanced relative performance. Switzerland-based asset manager Partners Group’s share price was supported by solid fiscal year 2018 results, including base management fees, EBITDA and dividend payouts that were above consensus estimates. Client demand remains strong for private market investments and Partners Group remains selective on asset purchases given structurally high valuations. AIA Group is a leading pan-Asian insurer. The company continues to benefit from strong demand for its products due to its dominant brand position and competitive advantages in distribution and product innovation, coupled with rising affluence and insurance penetration within Asia. Furthermore, China announced plans to further open up its insurance markets to foreign competition, booting sentiment in the sector. France aircraft manufacturer Airbus SE led performance within the Industrials sector. Product transitions to the next generation of aircrafts that have pressured earnings and cash flows at the company over the last several years have peaked, leaving Airbus in a favorable position where investment is moderating and profitability is poised to improve. Partially offsetting these effects were underweight allocations to Europe and Japan, which outperformed the Index during the period, coupled with below average stock selection within the Communication Services and Energy sectors. Within the Communications Services sector, Canadian telecom company Rogers Communications, Inc. detracted from performance, as the share price was hampered by weaker wireless subscriber growth. While still generally healthy, the wireless market outlook is more moderated in 2019 versus the prior two years where we saw solid subscriber growth and strong pricing trends. Returns from Rogers’ wireless segment in the first quarter of 2019, coupled with some market share loss, underscored this reality. We sold the position as a result. Within Energy, Canada-based oil and gas company Enerplus Corporation detracted from performance, due to weaker oil prices and mixed financial results. Enerplus’s overall production declined 9.5% sequentially as the company lowered operating activity following weaker oil pricing. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

46 Semiannual Report June 30, 2019

Institutional International Developed Plus Fund (In Liquidation)

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019

	Year to Date			1 Year			3 Year			5 Year			10 Year
Institutional International Developed Plus Fund		20.69	%		3.43	%		8.92	%		3.74	%		7.63	%
MSCI World Ex-U.S. Index (net)		14.64			1.29			9.01			2.04			6.75

During the first quarter of 2018, the Fund received a litigation settlement that positively impacted the Fund’s performance. This was a one-time event that is not likely to be repeated. With the passage of time the impact of this settlement on the Fund’s performance is likely to diminish.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Shares of the Fund are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) World Ex-U.S. Index (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 47

Institutional International Developed Plus Fund (In Liquidation)

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe—38.4%
	Denmark—1.8%
	DSV A/S (Road & rail)		3,696	$	363
	France—8.9%
	Airbus SE (Aerospace & defense)		3,998		567
	Capgemini SE (IT services)		3,268		406
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		1,014		432
	Safran S.A. (Aerospace & defense)		2,850		417
					1,822
	Germany—8.6%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		18,542		328
	MTU Aero Engines AG (Aerospace & defense)		2,947		702
*	QIAGEN N.V. (Life sciences tools & services)†		5,886		239
	SAP SE (Software)		3,685		506
					1,775
	Ireland—4.1%
	Accenture plc Class “A” (IT services)†		1,835		339
	Kerry Group plc Class “A” (Food products)		4,281		511
					850
	Netherlands—3.1%
*	Adyen N.V. (IT services)		178		137
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		15,586		509
					646
	Sweden—1.5%
	Atlas Copco AB Class “A” (Machinery)		9,564		306
	Switzerland—10.4%
*	Alcon, Inc. (Health care equipment & supplies)		5,243		324
	Novartis AG (Pharmaceuticals)		4,397		402
	Partners Group Holding AG (Capital markets)		894		702
	Straumann Holding AG (Health care equipment & supplies)		463		409
	Tecan Group AG (Life sciences tools & services)		1,119		290
					2,127
	United Kingdom—17.2%
	AstraZeneca plc (Pharmaceuticals)		7,002		572
	Compass Group plc (Hotels, restaurants & leisure)		37,397		896
	Diageo plc (Beverages)		20,939		900
	Halma plc (Electronic equipment, instruments & components)		15,487		397
	Legal & General Group plc (Insurance)		75,028		257
	Prudential plc (Insurance)		22,895		499
					3,521

	Issuer	Shares		Value
	Common Stocks—(continued)
	Japan—9.7%
	Daikin Industries, Ltd. (Building products)		3,406	$	445
	Hoya Corporation (Health care equipment & supplies)		4,900		375
	Keyence Corporation (Electronic equipment, instruments & components)		900		552
	Nihon M&A Center, Inc. (Professional services)		9,600		230
	Shiseido Co., Ltd. (Personal products)		5,300		399
					2,001
	Canada—9.4%
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		8,334		398
	Canadian National Railway Co. (Road & rail)†		8,939		827
	The Toronto-Dominion Bank (Banks)†		12,026		702
					1,927
	Asia—8.2%
	Australia—4.4%
	CSL, Ltd. (Biotechnology)		3,026		457
	Goodman Group (Equity REIT)		42,190		445
					902
	Hong Kong—3.8%
	AIA Group, Ltd. (Insurance)		72,471		782
	Emerging Asia—7.1%
	China—2.1%
*	Alibaba Group Holding, Ltd.-ADR (Internet & direct marketing retail)		2,592		439
	India—2.5%
	HDFC Bank, Ltd.-ADR (Banks)		3,923		510
	Taiwan—2.5%
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		13,050		511
	Emerging Latin America—1.3%
	Peru—1.3%
	Credicorp, Ltd. (Banks)†		1,189		271
	Total Common Stocks—91.3% (cost $14,801)				18,753

See accompanying Notes to Financial Statements.

48 Semiannual Report June 30, 2019

Institutional International Developed Plus Fund (In Liquidation)

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $1,760, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$1,760	$	1,760
Total Repurchase Agreement—8.6% (cost $1,760)				1,760
Total Investments—99.9% (cost $16,561)				20,513
Cash and other assets, less liabilities—0.1%				16
Net assets—100.0%			$	20,529

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Financials	22.0	%
Industrials	20.5	%
Information Technology	16.9	%
Health Care	16.4	%
Consumer Staples	9.7	%
Consumer Discretionary	9.4	%
Energy	2.7	%
Real Estate	2.4	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	24.1	%
U.S. Dollar	22.6	%
British Pound Sterling	18.8	%
Swiss Franc	11.3	%
Japanese Yen	10.7	%
Australian Dollar	4.8	%
Hong Kong Dollar	4.2	%
Danish Krone	1.9	%
Swedish Krona	1.6	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 49

	International Growth Fund
	The International Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Simon Fennell Kenneth J. McAtamney	The William Blair International Growth Fund (Class N shares) posted a 19.27% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI Index (net) (the “Index”), increased 13.33%.
	Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Financials, Industrials and Consumer Discretionary sectors were the most notable contributors to relative return. Within Financials, Ping An Insurance Group Co. of China, Ltd., an integrated financial services platform comprising insurance, banking and asset management businesses propelled relative results, as the company posted strong operating results in the first quarter.
	Within Industrials, Airbus SE was an additional source of outperformance. Product transitions to the next generation of aircrafts that have pressured earnings and cash flows at the company over the last several years have peaked, leaving the company in a favorable position where investment is moderating and profitability is poised to improve.
	Within the Consumer Discretionary sector, Li Ning Co., Ltd. enhanced the Fund’s relative performance. Li Ning sells footwear, apparel, equipment, and accessories for professional and leisure purposes, primarily under the LI-NING brand. The company is in the fourth year of a major turnaround with growth from here most likely to be driven by margin expansion. Overall, the consumer spending environment is supportive and Li Ning is making significant strides in strengthening its execution capabilities in e-commerce and new product development (kids’ and women’s).
	Partially offsetting these positive effects were underweight allocations to the Emerging Asia region and the Financials sector, coupled with below average stock selection within the Communication Services sector. Within the Communication Services sector, Rogers Communications, Inc., an industry leader with high quality customers and a favorable spectrum position in Canada, reported soft wireless subscription growth, leading us to trim the position.
	Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

50 Semiannual Report June 30, 2019

International Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		19.27	%		(0.43	)%		8.44	%		2.84	%		8.04	%		—
Class I		19.44			(0.10	)		8.78			3.14			8.36			—
Class R6		—			—			—			—			—			2.10	%
MSCI ACW Ex-U.S. IMI (net)		13.33			0.26			9.17			2.25			6.78			(0.01	)

(a) Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) All Country World (ACW) Ex-U.S. Investable Market Index (IMI) (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed and emerging markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

 

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 51

International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe, Mid-East—42.6%
	Belgium—0.1%
	Melexis N.V. (Semiconductors & semiconductor equipment)		39,947	$	2,703
	Warehouses De Pauw CVA (Equity REIT)		2,558		430
					3,133
	Denmark—3.7%
	Ambu A/S Class “B” (Health care equipment & supplies)		46,975		761
	Chr Hansen Holding A/S (Chemicals)		98,960		9,293
	Coloplast A/S Class “B” (Health care equipment & supplies)		124,759		14,099
	DSV A/S (Road & rail)		205,404		20,171
*	Genmab A/S (Biotechnology)		61,795		11,363
	Orsted A/S (Electric utilities)		196,973		17,032
	Royal Unibrew A/S (Beverages)		57,254		4,178
	Tryg A/S (Insurance)		108,622		3,531
					80,428
	Finland—0.8%
	Neste Oyj (Oil, gas & consumable fuels)		519,865		17,640
	France—11.2%
	Airbus SE (Aerospace & defense)		246,257		34,913
	Alten S.A. (IT services)		26,134		3,132
	Capgemini SE (IT services)		183,676		22,839
	Dassault Systemes SE (Software)		113,831		18,160
	Hermes International (Textiles, apparel & luxury goods)		11,894		8,577
	Ipsen S.A. (Pharmaceuticals)		36,122		4,929
	Kering S.A. (Textiles, apparel & luxury goods)		35,507		20,999
	L’Oreal S.A. (Personal products)		94,196		26,831
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		73,279		31,189
	Nexity S.A. (Real estate management & development)		36,865		1,593
	Orpea (Health care providers & services)		51,501		6,213
	Rubis SCA (Gas utilities)		68,282		3,845
	Safran S.A. (Aerospace & defense)		189,236		27,726
	Teleperformance (Professional services)		50,870		10,192
	Thales S.A. (Aerospace & defense)		140,292		17,333
*	Worldline S.A. (IT services)		54,564		3,971
					242,442
	Germany—5.0%
	Carl Zeiss Meditec AG (Health care equipment & supplies)		54,902		5,416
	GRENKE AG (Diversified financial services)		25,680		2,756
	KION Group AG (Machinery)		59,381		3,743
	MTU Aero Engines AG (Aerospace & defense)		94,098		22,416
	Puma SE (Textiles, apparel & luxury goods)		99,622		6,644
*	QIAGEN N.V. (Life sciences tools & services)†		303,792		12,319
	SAP SE (Software)		233,970		32,128

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Germany—(continued)
	Vonovia SE (Real estate management & development)		466,407	$	22,275
	Washtec AG (Machinery)		16,765		1,140
					108,837
	Ireland—1.8%
*	ICON plc (Life sciences tools & services)†		82,595		12,717
	Kerry Group plc Class “A” (Food products)		110,087		13,144
	Kingspan Group plc (Building products)		222,160		12,065
					37,926
	Israel—1.2%
*	Check Point Software Technologies, Ltd. (Software)†		135,746		15,693
*	CyberArk Software, Ltd. (Software)†		25,185		3,220
*	Wix.com, Ltd. (IT services)†		47,924		6,810
					25,723
	Italy—1.9%
	Amplifon SpA (Health care providers & services)		103,777		2,426
	Banca Generali SpA (Capital markets)		165,635		4,769
	Enel SpA (Electric utilities)		1,555,640		10,861
	Ferrari N.V. (Automobiles)		70,945		11,520
	Interpump Group SpA (Machinery)		116,415		3,582
	Moncler SpA (Textiles, apparel & luxury goods)		99,363		4,248
	Technogym SpA (Leisure products)		273,518		3,045
					40,451
	Luxembourg—0.3%
	Tenaris S.A. (Energy equipment & services)		440,726		5,768
	Netherlands—5.0%
*	Adyen N.V. (IT services)		11,091		8,558
	ASML Holding N.V. (Semiconductors & semiconductor equipment)		123,850		25,876
	Euronext N.V. (Capital markets)		57,967		4,387
	Koninklijke Philips N.V. (Health care equipment & supplies)		500,214		21,720
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		853,155		27,852
	Wolters Kluwer N.V. (Professional services)		275,864		20,082
					108,475
	Spain—1.9%
	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		302,333		12,070
	Amadeus IT Group S.A. (IT services)		354,576		28,086
					40,156

See accompanying Notes to Financial Statements.

52 Semiannual Report June 30, 2019

International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Sweden—2.9%
	Atlas Copco AB Class “A” (Machinery)		551,774	$	17,636
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		231,325		4,579
	Fabege AB (Real estate management & development)		297,615		4,479
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		278,568		15,467
	Indutrade AB (Trading companies & distributors)		137,385		4,391
	Lifco AB Class “B” (Industrial conglomerates)		37,904		2,100
	Nibe Industrier AB Class “B” (Building products)		252,727		3,700
	Nolato AB Class “B” (Industrial conglomerates)		50,999		3,111
*	Swedish Orphan Biovitrum AB (Biotechnology)		247,417		4,765
	Vitrolife AB (Biotechnology)		133,508		2,602
					62,830
	Switzerland—6.8%
*	Alcon, Inc. (Health care equipment & supplies)		167,198		10,325
	Belimo Holding AG (Building products)		465		2,858
	Logitech International S.A. (Technology hardware, storage & peripherals)		174,816		6,986
*	Lonza Group AG (Life sciences tools & services)		98,423		33,211
	Novartis AG (Pharmaceuticals)		372,053		33,996
	Partners Group Holding AG (Capital markets)		22,915		18,004
	Sika AG (Chemicals)		116,523		19,886
	Tecan Group AG (Life sciences tools & services)		9,705		2,517
*	Temenos AG (Software)		89,664		16,042
*	VAT Group AG (Machinery)		34,569		4,258
					148,083
	Emerging Asia—15.1%
	China—9.9%
*	Alibaba Group Holding, Ltd.-ADR (Internet & direct marketing retail)		240,264		40,713
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		2,955,900		4,648
*	China Mengniu Dairy Co., Ltd. (Food products)		1,893,000		7,331
	China Merchants Bank Co., Ltd. Class “H” (Banks)		4,843,500		24,150
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		1,696,000		3,921
	Huazhu Group, Ltd.-ADR (Hotels, restaurants & leisure)		111,760		4,051
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		95,953		13,747

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	China—(continued)
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		3,854,000	$	9,088
	NetEase, Inc.—ADR (Entertainment)		58,994		15,089
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		2,651,500		31,838
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		600,000		8,249
	Tencent Holdings, Ltd. (Interactive Media & Services)		988,200		44,605
*	Tencent Music Entertainment Group-ADR (Entertainment)		215,616		3,232
	Vitasoy International Holdings, Ltd. (Food products)		610,000		2,932
					213,594
	India—1.7%
	HDFC Bank, Ltd. (Banks)		314,520		11,122
	Hexaware Technologies, Ltd. (IT services)		545,847		2,983
	Hindustan Unilever, Ltd. (Household products)		278,220		7,210
	Maruti Suzuki India, Ltd. (Automobiles)		67,132		6,360
	Pidilite Industries, Ltd. (Chemicals)		208,010		3,664
	Titan Co., Ltd. (Textiles, apparel & luxury goods)		296,246		5,714
					37,053
	Indonesia—1.1%
	PT Astra International Tbk (Automobiles)		1,427,300		753
	PT Bank Central Asia Tbk (Banks)		11,466,200		24,328
					25,081
	South Korea—0.4%
	Samsung SDI Co., Ltd. (Electronic equipment, instruments & components)		39,355		8,061
	Taiwan—1.5%
	Eclat Textile Co., Ltd. (Textiles, apparel & luxury goods)		268,000		3,434
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		737,405		28,884
					32,318
	Thailand—0.5%
	Airports of Thailand PCL (Transportation infrastructure)		1,861,200		4,461
	Bangkok Dusit Medical Services PCL Class “F” (Health care providers & services)		4,394,500		3,725
	Tisco Financial Group PCL (Banks)		1,100,700		3,356
					11,542

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 53

International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Shares		Value
Common Stocks—(continued)
United Kingdom—14.6%
3i Group plc (Capital markets)		701,412	$	9,919
Abcam plc (Biotechnology)		178,637		3,344
Avast plc (Software)		764,391		2,912
AVEVA Group plc (Software)		137,305		7,048
Beazley plc (Insurance)		708,765		4,964
Big Yellow Group plc (Equity REIT)		345,477		4,341
Burford Capital, Ltd. (Capital markets)		212,987		4,192
Close Brothers Group plc (Capital markets)		139,034		2,497
Compass Group plc (Hotels, restaurants & leisure)		1,460,072		34,989
Croda International plc (Chemicals)		142,909		9,292
Diageo plc (Beverages)		719,497		30,920
Experian plc (Professional services)		1,028,981		31,153
Fevertree Drinks plc (Beverages)		127,370		3,749
Greggs plc (Hotels, restaurants & leisure)		317,667		9,271
Halma plc (Electronic equipment, instruments & components)		473,211		12,139
Hiscox, Ltd. (Insurance)		429,058		9,219
Intermediate Capital Group plc (Capital markets)		398,888		6,996
Intertek Group plc (Professional services)		93,911		6,562
London Stock Exchange Group plc (Capital markets)		233,267		16,252
Melrose Industries plc (Electrical equipment)		3,608,177		8,287
RELX plc (Professional services)		1,017,608		24,677
Renishaw plc (Electronic equipment, instruments & components)		60,428		3,268
Rentokil Initial plc (Commercial services & supplies)		2,263,393		11,426
Rotork plc (Machinery)		1,273,319		5,120
Segro plc (Equity REIT)		1,374,124		12,742
Softcat plc (IT services)		212,857		2,626
Spirax-Sarco Engineering plc (Machinery)		83,503		9,740
SSP Group plc (Hotels, restaurants & leisure)		506,182		4,410
St James’s Place plc (Capital markets)		723,232		10,085
The Weir Group plc (Machinery)		256,452		5,037
Victrex plc (Chemicals)		190,582		5,237
WH Smith plc (Specialty retail)		185,552		4,642
				317,056
Japan—10.6%
Asahi Intecc Co., Ltd. (Health care equipment & supplies)		368,400		9,069
Daikin Industries, Ltd. (Building products)		129,500		16,894
Digital Arts, Inc. (Software)		23,200		2,044
GMO Payment Gateway, Inc. (IT services)		64,900		4,461
Harmonic Drive Systems, Inc. (Machinery)		107,600		4,147
Hoya Corporation (Health care equipment & supplies)		301,600		23,090
Keyence Corporation (Electronic equipment, instruments & components)		55,100		33,796
M3, Inc. (Health care technology)		276,100		5,042
MISUMI Group, Inc. (Machinery)		276,000		6,917
MonotaRO Co., Ltd. (Trading companies & distributors)		174,000		4,238

	Issuer	Shares		Value
	Common Stocks—(continued)
	Japan—(continued)
	Nichias Corporation (Building products)		105,700	$	1,899
	Nihon M&A Center, Inc. (Professional services)		206,500		4,949
	Nitori Holdings Co., Ltd. (Specialty retail)		43,400		5,748
	Nomura Research Institute, Ltd. (IT services)		379,500		6,079
	Sankyu, Inc. (Road & rail)		76,520		4,017
	Shimadzu Corporation (Electronic equipment, instruments & components)		217,000		5,318
	Shiseido Co., Ltd. (Personal products)		294,600		22,190
	SMC Corporation (Machinery)		38,700		14,419
	TechnoPro Holdings, Inc. (Professional services)		142,400		7,555
	Terumo Corporation (Health care equipment & supplies)		675,300		20,106
	TIS, Inc. (IT services)		152,600		7,770
	Yakult Honsha Co., Ltd. (Food products)		164,700		9,700
	Zenkoku Hosho Co., Ltd. (Diversified financial services)		94,700		3,632
	ZOZO Inc. (Internet & direct marketing retail)		282,800		5,296
					228,376
	Canada—6.7%
	Alimentation Couche-Tard, Inc. Class “B” (Food & staples retailing)		334,757		21,066
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		553,360		26,440
	Canadian National Railway Co. (Road & rail)		279,058		25,827
	Canadian Pacific Railway, Ltd. (Road & rail)†		77,407		18,209
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		49,272		8,879
	Rogers Communications, Inc. Class “B” (Wireless telecommunication services)		406,313		21,750
	The Bank of NT Butterfield & Son, Ltd. (Banks)†		39,637		1,346
	The Toronto-Dominion Bank (Banks)		355,058		20,747
					144,264
	Asia—5.3%
	Australia—2.6%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		423,329		9,130
	CSL, Ltd. (Biotechnology)		138,657		20,929
	Goodman Group (Equity REIT)		863,748		9,114
	Macquarie Group, Ltd. (Capital markets)		200,714		17,669
					56,842
	Hong Kong—2.5%
	AIA Group, Ltd. (Insurance)		3,956,800		42,674
	Galaxy Entertainment Group, Ltd. (Hotels, restaurants & leisure)		1,666,000		11,229
					53,903

See accompanying Notes to Financial Statements.

54 Semiannual Report June 30, 2019

International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Asia—(continued)
	New Zealand—0.2%
	Auckland International Airport, Ltd. (Transportation infrastructure)		515,984	$	3,414
	Emerging Latin America—2.1%
	Argentina—0.2%
*	Globant S.A. (Software)†		41,334		4,177
	Brazil—1.0%
	B3 S.A.-Brasil Bolsa Balcao (Capital markets)		910,100		8,878
	Localiza Rent a Car S.A. (Road & rail)		444,400		4,743
	Lojas Renner S.A. (Multiline retail)		365,100		4,484
	Magazine Luiza S.A. (Multiline retail)		78,900		4,338
					22,443
	Mexico—0.2%
	Grupo Aeroportuario del Sureste S.A.B. de C.V.-ADR (Transportation infrastructure)		25,206		4,086
	Peru—0.7%
	Credicorp, Ltd. (Banks)†		62,032		14,200
	Emerging Europe, Mid-East, Africa—1.3%
	Russia—0.4%
*	Yandex N.V. Class “A” (Interactive Media & Services)†		241,715		9,185
	South Africa—0.7%
	Bid Corporation, Ltd. (Food & staples retailing)		160,187		3,491
	Bidvest Group, Ltd. (Industrial conglomerates)		160,187		2,154
	Mr. Price Group, Ltd. (Specialty retail)		215,102		3,032
	RMB Holdings, Ltd. (Diversified financial services)		1,002,657		6,008
					14,685
	United Arab Emirates—0.2%
	First Abu Dhabi Bank PJSC (Banks)		1,266,854		5,125
	Total Common Stocks—98.3% (cost $1,736,828)				2,127,297
	Rights
	Spain—0.0%
*	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		305,556		479
	Total Rights—0.0% (cost $504)				479

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $10,767, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$10,766	$	10,766
Total Repurchase Agreement—0.5% (cost $10,766)				10,766
Total Investments—98.8% (cost $1,748,098)				2,138,542
Cash and other assets, less liabilities—1.2%				26,374
Net assets—100.0%			$	2,164,916

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	21.9	%
Information Technology	16.0	%
Financials	15.9	%
Consumer Discretionary	12.9	%
Health Care	12.4	%
Consumer Staples	7.8	%
Communication Services	4.4	%
Real Estate	2.6	%
Energy	2.4	%
Materials	2.2	%
Utilities	1.5	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	27.3	%
British Pound Sterling	14.9	%
U.S. Dollar	10.8	%
Japanese Yen	10.7	%
Hong Kong Dollar	8.7	%
Swiss Franc	7.0	%
Canadian Dollar	4.2	%
Danish Krone	3.8	%
Swedish Krona	2.9	%
Australian Dollar	2.7	%
Indian Rupee	1.7	%
Indonesian Rupiah	1.2	%
Brazilian Real	1.1	%
All Other Currencies	3.0	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 55

	Institutional International Growth Fund
	The Institutional International Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Simon Fennell Kenneth J. McAtamney	The William Blair Institutional International Growth Fund posted a 19.40% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI Index (net) (the “Index”), increased 13.33%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Financials, Industrials and Consumer Discretionary sectors were the most notable contributors to relative return. Within Financials, Ping An Insurance Group Co. of China, Ltd., an integrated financial services platform comprising insurance, banking and asset management businesses propelled relative results, as the company posted strong operating results in the first quarter. Within Industrials, Airbus SE was an additional source of outperformance. Product transitions to the next generation of aircrafts that have pressured earnings and cash flows at the company over the last several years have peaked, leaving the company in a favorable position where investment is moderating and profitability is poised to improve. Within the Consumer Discretionary sector, Li Ning Co., Ltd. enhanced the Fund’s relative performance. Li Ning sells footwear, apparel, equipment, and accessories for professional and leisure purposes, primarily under the LI-NING brand. The company is in the fourth year of a major turnaround with growth from here most likely to be driven by margin expansion. Overall, the consumer spending environment is supportive and Li Ning is making significant strides in strengthening its execution capabilities in e-commerce and new product development (kids’ and women’s). Partially offsetting these positive effects were underweight allocations to the Emerging Asia region and the Financials sector, coupled with below average stock selection within the Communication Services sector. Within the Communication Services sector, Rogers Communications, Inc., an industry leader with high quality customers and a favorable spectrum position in Canada, reported soft wireless subscription growth, leading us to trim the position. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

56 Semiannual Report June 30, 2019

Institutional International Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date		1 Year		3 Year		5 Year		10 Year
Institutional International Growth Fund	19.40	%	0.11	%	8.90	%	3.28	%	8.53	%
MSCI ACW Ex-U.S. IMI (net)	13.33		0.26		9.17		2.25		6.78

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Investing in smaller and medium capitalization companies involves special risks, including higher volatility and lower liquidity. Smaller and medium capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. Shares of the Fund are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) All Country World (ACW) Ex-U.S. Investable Market Index (IMI) (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed and emerging markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 57

Institutional International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe, Mid-East—42.8%
	Belgium—0.1%
	Melexis N.V. (Semiconductors & semiconductor equipment)		33,329	$	2,255
	Warehouses De Pauw CVA (Equity REIT)		2,115		356
					2,611
	Denmark—3.7%
	Ambu A/S Class “B” (Health care equipment & supplies)		38,780		628
	Chr Hansen Holding A/S (Chemicals)		82,566		7,753
	Coloplast A/S Class “B” (Health care equipment & supplies)		104,090		11,763
	DSV A/S (Road & rail)		171,375		16,829
*	Genmab A/S (Biotechnology)		51,558		9,481
	Orsted A/S (Electric utilities)		164,342		14,211
	Royal Unibrew A/S (Beverages)		47,769		3,486
	Tryg A/S (Insurance)		90,628		2,946
					67,097
	Finland—0.8%
	Neste Oyj (Oil, gas & consumable fuels)		433,741		14,717
	France—11.3%
	Airbus SE (Aerospace & defense)		205,460		29,129
	Alten S.A. (IT services)		21,600		2,589
	Capgemini SE (IT services)		153,247		19,055
	Dassault Systemes SE (Software)		94,973		15,151
	Hermes International (Textiles, apparel & luxury goods)		9,924		7,157
	Ipsen S.A. (Pharmaceuticals)		30,137		4,112
	Kering S.A. (Textiles, apparel & luxury goods)		29,625		17,520
	L’Oreal S.A. (Personal products)		78,590		22,386
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		61,139		26,022
	Nexity S.A. (Real estate management & development)		30,434		1,315
	Orpea (Health care providers & services)		42,968		5,184
	Rubis SCA (Gas utilities)		56,971		3,208
	Safran S.A. (Aerospace & defense)		157,886		23,133
	Teleperformance (Professional services)		42,443		8,504
	Thales S.A. (Aerospace & defense)		117,051		14,461
*	Worldline S.A. (IT services)		45,525		3,313
					202,239
	Germany—5.0%
	Carl Zeiss Meditec AG (Health care equipment & supplies)		45,806		4,519
	GRENKE AG (Diversified financial services)		21,225		2,278
	KION Group AG (Machinery)		49,543		3,123
	MTU Aero Engines AG (Aerospace & defense)		78,510		18,703
	Puma SE (Textiles, apparel & luxury goods)		83,120		5,543
*	QIAGEN N.V. (Life sciences tools & services)†		253,463		10,278
	SAP SE (Software)		195,209		26,806

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Germany—(continued)
	Vonovia SE (Real estate management & development)		389,254	$	18,590
	Washtec AG (Machinery)		13,840		941
					90,781
	Ireland—1.8%
*	ICON plc (Life sciences tools & services)†		68,912		10,611
	Kerry Group plc Class “A” (Food products)		91,849		10,966
	Kingspan Group plc (Building products)		185,355		10,066
					31,643
	Israel—1.2%
*	Check Point Software Technologies, Ltd. (Software)†		113,258		13,094
*	CyberArk Software, Ltd. (Software)†		21,012		2,686
*	Wix.com, Ltd. (IT services)†		39,984		5,682
					21,462
	Italy—1.9%
	Amplifon SpA (Health care providers & services)		85,811		2,006
	Banca Generali SpA (Capital markets)		138,195		3,979
	Enel SpA (Electric utilities)		1,297,924		9,062
	Ferrari N.V. (Automobiles)		59,192		9,612
	Interpump Group SpA (Machinery)		95,306		2,933
	Moncler SpA (Textiles, apparel & luxury goods)		82,902		3,544
	Technogym SpA (Leisure products)		228,206		2,540
					33,676
	Luxembourg—0.3%
	Tenaris S.A. (Energy equipment & services)		367,714		4,812
	Netherlands—5.0%
*	Adyen N.V. (IT services)		9,255		7,142
	ASML Holding N.V. (Semiconductors & semiconductor equipment)		103,333		21,590
	Euronext N.V. (Capital markets)		48,170		3,645
	Koninklijke Philips N.V. (Health care equipment & supplies)		417,347		18,121
	Royal Dutch Shell plc Class “A” (Oil, gas & consumable fuels)		711,818		23,238
	Wolters Kluwer N.V. (Professional services)		230,163		16,755
					90,491
	Spain—1.9%
	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		252,247		10,071
	Amadeus IT Group S.A. (IT services)		295,836		23,433
					33,504
	Sweden—2.9%
	Atlas Copco AB Class “A” (Machinery)		460,364		14,714
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		192,227		3,805

See accompanying Notes to Financial Statements.

58 Semiannual Report June 30, 2019

Institutional International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Sweden—(continued)
	Fabege AB (Real estate management & development)		248,311	$	3,737
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		232,419		12,904
	Indutrade AB (Trading companies & distributors)		114,165		3,649
	Lifco AB Class “B” (Industrial conglomerates)		31,329		1,736
	Nibe Industrier AB Class “B” (Building products)		210,859		3,087
	Nolato AB Class “B” (Industrial conglomerates)		42,132		2,570
*	Swedish Orphan Biovitrum AB (Biotechnology)		206,429		3,976
	Vitrolife AB (Biotechnology)		111,391		2,171
					52,349
	Switzerland—6.9%
*	Alcon, Inc. (Health care equipment & supplies)		139,500		8,614
	Belimo Holding AG (Building products)		388		2,385
	Logitech International S.A. (Technology hardware, storage & peripherals)		145,856		5,828
*	Lonza Group AG (Life sciences tools & services)		82,118		27,709
	Novartis AG (Pharmaceuticals)		310,417		28,364
	Partners Group Holding AG (Capital markets)		19,118		15,021
	Sika AG (Chemicals)		97,219		16,592
	Tecan Group AG (Life sciences tools & services)		8,021		2,080
*	Temenos AG (Software)		74,809		13,384
*	VAT Group AG (Machinery)		28,842		3,553
					123,530
	Emerging Asia—15.2%
	China—9.9%
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		200,460		33,968
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		2,457,000		3,863
*	China Mengniu Dairy Co., Ltd. (Food products)		1,580,000		6,118
	China Merchants Bank Co., Ltd. Class “H” (Banks)		4,041,500		20,151
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		1,414,000		3,269
	Huazhu Group, Ltd.—ADR (Hotels, restaurants & leisure)		92,386		3,349
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		80,017		11,464
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		3,215,500		7,582
	NetEase, Inc.—ADR (Entertainment)		49,221		12,589
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		2,212,000		26,561

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	China—(continued)
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		500,900	$	6,887
	Tencent Holdings, Ltd. (Interactive Media & Services)		824,500		37,216
*	Tencent Music Entertainment Group-ADR (Entertainment)		179,896		2,697
	Vitasoy International Holdings, Ltd. (Food products)		508,000		2,442
					178,156
	India—1.7%
	HDFC Bank, Ltd. (Banks)		262,415		9,280
	Hexaware Technologies, Ltd. (IT services)		455,419		2,489
	Hindustan Unilever, Ltd. (Household products)		232,129		6,016
	Maruti Suzuki India, Ltd. (Automobiles)		56,010		5,306
	Pidilite Industries, Ltd. (Chemicals)		173,551		3,057
	Titan Co., Ltd. (Textiles, apparel & luxury goods)		247,168		4,767
					30,915
	Indonesia—1.2%
	PT Astra International Tbk (Automobiles)		1,178,268		621
	PT Bank Central Asia Tbk (Banks)		9,566,606		20,298
					20,919
	South Korea—0.4%
	Samsung SDI Co., Ltd. (Electronic equipment, instruments & components)		32,835		6,725
	Taiwan—1.5%
	Eclat Textile Co., Ltd. (Textiles, apparel & luxury goods)		223,000		2,858
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		615,244		24,099
					26,957
	Thailand—0.5%
	Airports of Thailand PCL (Transportation infrastructure)		1,552,900		3,722
	Bangkok Dusit Medical Services PCL Class “F” (Health care providers & services)		3,666,500		3,108
	Tisco Financial Group PCL (Banks)		909,800		2,774
					9,604
	United Kingdom—14.7%
	3i Group plc (Capital markets)		585,213		8,275
	Abcam plc (Biotechnology)		149,042		2,790
	Avast plc (Software)		637,758		2,430
	AVEVA Group plc (Software)		114,558		5,880
	Beazley plc (Insurance)		591,348		4,142
	Big Yellow Group plc (Equity REIT)		288,244		3,622
	Burford Capital, Ltd. (Capital markets)		177,605		3,496
	Close Brothers Group plc (Capital markets)		116,002		2,083
	Compass Group plc (Hotels, restaurants & leisure)		1,218,190		29,193

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 59

Institutional International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Shares		Value
Common Stocks—(continued)
United Kingdom—(continued)
Croda International plc (Chemicals)		119,234	$	7,753
Diageo plc (Beverages)		600,301		25,798
Experian plc (Professional services)		858,514		25,992
Fevertree Drinks plc (Beverages)		106,269		3,128
Greggs plc (Hotels, restaurants & leisure)		265,041		7,735
Halma plc (Electronic equipment, instruments & components)		394,816		10,128
Hiscox, Ltd. (Insurance)		357,978		7,692
Intermediate Capital Group plc (Capital markets)		332,807		5,837
Intertek Group plc (Professional services)		78,353		5,475
London Stock Exchange Group plc (Capital markets)		194,623		13,559
Melrose Industries plc (Electrical equipment)		3,010,429		6,914
RELX plc (Professional services)		849,026		20,589
Renishaw plc (Electronic equipment, instruments & components)		50,417		2,726
Rentokil Initial plc (Commercial services & supplies)		1,888,429		9,533
Rotork plc (Machinery)		1,062,376		4,271
Segro plc (Equity REIT)		1,146,480		10,632
Softcat plc (IT services)		176,016		2,172
Spirax-Sarco Engineering plc (Machinery)		69,670		8,127
SSP Group plc (Hotels, restaurants & leisure)		422,324		3,679
St James’s Place plc (Capital markets)		603,418		8,414
The Weir Group plc (Machinery)		213,967		4,202
Victrex plc (Chemicals)		159,009		4,370
WH Smith plc (Specialty retail)		154,812		3,873
				264,510
Japan—10.6%
Asahi Intecc Co., Ltd. (Health care equipment & supplies)		304,200		7,488
Daikin Industries, Ltd. (Building products)		108,000		14,089
Digital Arts, Inc. (Software)		19,100		1,683
GMO Payment Gateway, Inc. (IT services)		53,800		3,698
Harmonic Drive Systems, Inc. (Machinery)		89,900		3,465
Hoya Corporation (Health care equipment & supplies)		251,600		19,262
Keyence Corporation (Electronic equipment, instruments & components)		46,000		28,215
M3, Inc. (Health care technology)		227,800		4,160
MISUMI Group, Inc. (Machinery)		230,300		5,772
MonotaRO Co., Ltd. (Trading companies & distributors)		145,200		3,536
Nichias Corporation (Building products)		87,400		1,570
Nihon M&A Center, Inc. (Professional services)		172,200		4,127
Nitori Holdings Co., Ltd. (Specialty retail)		36,200		4,795
Nomura Research Institute, Ltd. (IT services)		313,200		5,017
Sankyu, Inc. (Road & rail)		63,760		3,347
Shimadzu Corporation (Electronic equipment, instruments & components)		181,000		4,435

	Issuer	Shares		Value
	Common Stocks—(continued)
	Japan—(continued)
	Shiseido Co., Ltd. (Personal products)		245,900	$	18,522
	SMC Corporation (Machinery)		32,200		11,997
	TechnoPro Holdings, Inc. (Professional services)		118,800		6,303
	Terumo Corporation (Health care equipment & supplies)		563,400		16,774
	TIS, Inc. (IT services)		127,300		6,482
	Yakult Honsha Co., Ltd. (Food products)		137,300		8,087
	Zenkoku Hosho Co., Ltd. (Diversified financial services)		79,100		3,034
	ZOZO Inc. (Internet & direct marketing retail)		236,000		4,419
					190,277
	Canada—6.7%
	Alimentation Couche-Tard, Inc. Class “B” (Food & staples retailing)		279,299		17,576
	Brookfield Asset Management, Inc. Class “A” (Capital markets)†		461,687		22,060
	Canadian National Railway Co. (Road & rail)		232,828		21,549
	Canadian Pacific Railway, Ltd. (Road & rail)†		64,582		15,192
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		41,109		7,408
	Rogers Communications, Inc. Class “B” (Wireless telecommunication services)		339,002		18,147
	The Bank of NT Butterfield & Son, Ltd. (Banks)†		32,723		1,111
	The Toronto-Dominion Bank (Banks)		296,237		17,310
					120,353
	Asia—5.3%
	Australia—2.6%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		353,198		7,617
	CSL, Ltd. (Biotechnology)		115,686		17,462
	Goodman Group (Equity REIT)		720,655		7,604
	Macquarie Group, Ltd. (Capital markets)		167,463		14,742
					47,425
	Hong Kong—2.5%
	AIA Group, Ltd. (Insurance)		3,301,063		35,602
	Galaxy Entertainment Group, Ltd. (Hotels, restaurants & leisure)		1,390,000		9,369
					44,971
	New Zealand—0.2%
	Auckland International Airport, Ltd. (Transportation infrastructure)		430,504		2,849

See accompanying Notes to Financial Statements.

60 Semiannual Report June 30, 2019

Institutional International Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Latin America—2.1%
	Argentina—0.2%
*	Globant S.A. (Software)†		34,163	$	3,452
	Brazil—1.0%
	B3 S.A. - Brasil Bolsa Balcao (Capital markets)		759,300		7,407
	Localiza Rent a Car S.A. (Road & rail)		370,700		3,956
	Lojas Renner S.A. (Multiline retail)		304,660		3,742
	Magazine Luiza S.A. (Multiline retail)		65,200		3,585
					18,690
	Mexico—0.2%
	Grupo Aeroportuario del Sureste S.A.B. de C.V.—ADR (Transportation infrastructure)		20,833		3,377
	Peru—0.7%
	Credicorp, Ltd. (Banks)†		51,755		11,847
	Emerging Europe, Mid-East, Africa—1.3%
	Russia—0.4%
*	Yandex N.V. Class “A” (Interactive Media & Services)†		201,671		7,663
	South Africa—0.7%
	Bid Corporation, Ltd. (Food & staples retailing)		133,650		2,913
	Bidvest Group, Ltd. (Industrial conglomerates)		133,650		1,797
	Mr. Price Group, Ltd. (Specialty retail)		179,468		2,529
	RMB Holdings, Ltd. (Diversified financial services)		836,552		5,013
					12,252
	United Arab Emirates—0.2%
	First Abu Dhabi Bank PJSC (Banks)		1,056,981		4,276
	Total Common Stocks—98.7% (cost $1,455,108)				1,774,130
	Rights
	Spain—0.0%
*	ACS Actividades de Construccion y Servicios S.A. (Construction & engineering)		252,247		396
	Total Rights—0.0% (cost $416)				396

Issuer	Principal Amount		Value
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $13,848, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$13,848	$	13,848
Total Repurchase Agreement—0.8% (cost $13,848)				13,848
Total Investments—99.5% (cost $1,469,372)				1,788,374
Cash and other assets, less liabilities—0.5%				8,943
Net assets—100.0%			$	1,797,317

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	21.9%
Information Technology	16.0%
Financials	15.9%
Consumer Discretionary	12.9%
Health Care	12.4%
Consumer Staples	7.8%
Communication Services	4.4%
Real Estate	2.6%
Energy	2.4%
Materials	2.2%
Utilities	1.5%
Total	100.0%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	27.3%
British Pound Sterling	14.9%
U.S. Dollar	10.8%
Japanese Yen	10.7%
Hong Kong Dollar	8.7%
Swiss Franc	7.0%
Canadian Dollar	4.2%
Danish Krone	3.8%
Swedish Krona	2.9%
Australian Dollar	2.7%
Indian Rupee	1.7%
Indonesian Rupiah	1.2%
Brazilian Real	1.1%
All Other Currencies	3.0%
Total	100.0%

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 61

	International Small Cap Growth Fund
	The International Small Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Simon Fennell Andrew G. Flynn	The William Blair International Small Cap Growth Fund (Class N shares) posted an 18.73% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. Small Cap Index (net) (the “Index”), increased 11.60%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. The Consumer Discretionary, Financials and Industrials sectors were the most notable contributors to the Fund’s relative return. Within Consumer Discretionary, Chinese sportswear company Li Ning Co., Ltd. was the leading contributor. Li Ning sells footwear, apparel, equipment, and accessories for professional and leisure purposes, primarily under the LI-NING brand. The company is in the fourth year of a major turnaround with growth from here most likely to be driven by margin expansion. Overall, the consumer spending environment is supportive and Li Ning is making significant strides in strengthening its execution capabilities in e-commerce and new product development (kids and women’s). Within Financials, Euronext N.V., a leading pan-European exchange, was an additional source of outperformance. Around 45% of Euronext’s revenue is generated from recurring, non-transaction businesses. Management’s operational execution has been solid with significant cost savings and margin expansion since the IPO in 2014. A strong balance sheet (net cash) provides significant optionality through bolt-on or larger M&A transactions to deliver on revenue diversification and accelerate growth. Within Industrials, Sweden-based Indutrade AB was the top contributor for the six-month period. Indutrade is a leader in the Northern European market for industrial component distribution. The company is differentiated by its high proportion of proprietary products (38% of sales), a range of product offerings from high-quality suppliers, and a technically-savvy sales team, all of which help to reinforce close relationships with customers. Partially offsetting these positive effects were weak stock selection in the Consumer Staples and Materials sectors. Within Consumer Staples, Costa Group Holdings, Ltd., Australia’s leading fresh produce and vegetable company, detracted from performance as the share price sold off on the company’s downward revision to earnings expectations for the fiscal year ended June 2019. The disappointment was driven by pricing weakness for key products including berries, tomatoes and avocados due to unfavorable demand and supply conditions. Within the Materials sector, U.K.-based Scapa Group plc was the largest detractor. Scapa is a niche-focused producer of specialty tapes, where competition is limited and new entrants are deterred by stringent technical specifications and lengthy qualification processes. As Scapa’s engineered products are used in mission-critical components but represent a small portion of overall costs, the company is able to maintain pricing power despite the large size of its customers (e.g. large cable manufacturers, automotive original equipment manufacturers (OEMs), consumer electronics companies). The share price was negatively impacted by the early termination of a large North American contract. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

62 Semiannual Report June 30, 2019

International Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		18.73	%		(6.34	)%		5.68	%		2.31	%		9.15	%
Class I		18.95			(6.11	)		6.00			2.60			9.47
Class R6		18.95			(6.06	)		6.08			2.69			9.64
MSCI ACW Ex-U.S. Small Cap Index (net)		11.60			(5.94	)		7.76			2.77			8.48

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Investing in smaller companies involves special risks, including higher volatility and lower liquidity. Smaller capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) All Country World (ACW) Ex-U.S. Small Cap Index (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of small capitalization developed and emerging markets, excluding the United States. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

June 30, 2019 William Blair Funds 63

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Europe, Mid-East—35.5%
	Belgium—2.0%
	Melexis N.V. (Semiconductors & semiconductor equipment)		34,550	$	2,338
	Warehouses De Pauw CVA (Equity REIT)		21,965		3,696
					6,034
	Denmark—3.1%
	Ambu A/S Class “B” (Health care equipment & supplies)		22,370		362
*	Netcompany Group A/S (Software)		89,660		3,611
	Royal Unibrew A/S (Beverages)		47,057		3,434
	Tryg A/S (Insurance)		67,936		2,209
					9,616
	Foroe Islands—0.7%
	Bakkafrost P/F (Food products)		36,336		2,028
	France—6.1%
	Alten S.A. (IT services)		49,911		5,982
	Ipsen S.A. (Pharmaceuticals)		15,910		2,171
	Nexity S.A. (Real estate management & development)		65,050		2,811
	Rubis SCA (Gas utilities)		65,411		3,683
*	Worldline S.A. (IT services)		59,384		4,322
					18,969
	Germany—3.6%
	AURELIUS Equity Opportunities SE & Co KGaA (Capital markets)		45,060		2,140
	Carl Zeiss Meditec AG (Health care equipment & supplies)		25,254		2,491
	CTS Eventim AG & Co. KGaA (Entertainment)		32,532		1,514
	GRENKE AG (Diversified financial services)		29,006		3,113
	Norma Group SE (Machinery)		44,290		1,835
					11,093
	Israel—2.7%
*	CyberArk Software, Ltd. (Software)†		14,284		1,826
	Elbit Systems, Ltd. (Aerospace & defense)		15,557		2,315
	Mizrahi Tefahot Bank, Ltd. (Banks)		109,152		2,516
*	Wix.com, Ltd. (IT services)†		12,956		1,841
					8,498
	Italy—2.1%
	Amplifon SpA (Health care providers & services)		168,595		3,942
	Brunello Cucinelli SpA (Textiles, apparel & luxury goods)		50,249		1,695
	Technogym SpA (Leisure products)		76,569		852
					6,489
	Jersey—0.9%
	Sanne Group plc (Capital markets)		297,172		2,653

	Issuer	Shares		Value
	Common Stocks—(continued)
	Europe, Mid-East—(continued)
	Netherlands—2.8%
*	Basic-Fit N.V. (Hotels, restaurants & leisure)		63,293	$	2,227
	Euronext N.V. (Capital markets)		84,280		6,378
					8,605
	Sweden—7.9%
	Biotage AB (Life sciences tools & services)		68,871		808
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		224,469		4,443
	Indutrade AB (Trading companies & distributors)		191,771		6,129
	Lifco AB Class “B” (Industrial conglomerates)		32,767		1,815
	Nibe Industrier AB Class “B” (Building products)		163,510		2,394
	Nolato AB Class “B” (Industrial conglomerates)		40,808		2,489
*	Swedish Orphan Biovitrum AB (Biotechnology)		94,610		1,822
	Thule Group AB (Leisure products)		135,352		3,344
	Vitrolife AB (Biotechnology)		65,339		1,274
					24,518
	Switzerland—3.6%
*	Galenica AG (Pharmaceuticals)		51,472		2,584
	Kardex AG (Machinery)		16,547		2,888
	Tecan Group AG (Life sciences tools & services)		15,221		3,948
*	VAT Group AG (Machinery)		12,592		1,551
					10,971
	Japan—17.5%
	Asahi Intecc Co., Ltd. (Health care equipment & supplies)		155,000		3,816
	Benefit One, Inc. (Professional services)		142,400		2,454
	Digital Arts, Inc. (Software)		25,100		2,212
	GMO Payment Gateway, Inc. (IT services)		33,000		2,268
	Harmonic Drive Systems, Inc. (Machinery)		51,300		1,977
	Kose Corporation (Personal products)		10,300		1,726
	Matsumotokiyoshi Holdings Co., Ltd. (Food & staples retailing)		119,200		3,483
	Meitec Corporation (Professional services)		35,700		1,831
	MonotaRO Co., Ltd. (Trading companies & distributors)		67,300		1,639
	Nihon M&A Center, Inc. (Professional services)		167,200		4,007
	Nihon Unisys, Ltd. (IT services)		182,500		6,119
	PALTAC Corporation (Distributors)		83,600		4,591
	Park24 Co., Ltd. (Commercial services & supplies)		82,900		1,929
	Sankyu, Inc. (Road & rail)		32,520		1,707
	Stanley Electric Co., Ltd. (Auto components)		57,900		1,422

See accompanying Notes to Financial Statements.

64 Semiannual Report June 30, 2019

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Japan—(continued)
	TechnoPro Holdings, Inc. (Professional services)		47,400	$	2,515
	TIS, Inc. (IT services)		93,800		4,776
	Tokyo Century Corporation (Diversified financial services)		74,700		3,149
	United Arrows, Ltd. (Specialty retail)		72,800		2,272
					53,893
	United Kingdom—17.4%
	Abcam plc (Biotechnology)		186,918		3,499
	Avast plc (Software)		640,720		2,441
	AVEVA Group plc (Software)		84,642		4,345
	Beazley plc (Insurance)		752,942		5,273
	Big Yellow Group plc (Equity REIT)		168,816		2,121
	Burford Capital, Ltd. (Capital markets)		166,326		3,274
	Diploma plc (Trading companies & distributors)		184,185		3,583
	Electrocomponents plc (Electronic equipment, instruments & components)		432,892		3,479
	Fevertree Drinks plc (Beverages)		65,746		1,935
	Hill & Smith Holdings plc (Metals & mining)		114,662		1,705
	Intermediate Capital Group plc (Capital markets)		158,976		2,788
	Renishaw plc (Electronic equipment, instruments & components)		26,698		1,444
	Rotork plc (Machinery)		610,575		2,455
	Safestore Holdings plc (Equity REIT)		91,633		714
	Scapa Group plc (Chemicals)		287,914		678
	Softcat plc (IT services)		195,798		2,416
	SSP Group plc (Hotels, restaurants & leisure)		466,842		4,067
	The UNITE Group plc (Equity REIT)		336,525		4,165
	Victrex plc (Chemicals)		69,788		1,918
	Workspace Group plc (Equity REIT)		122,393		1,359
					53,659
	Emerging Asia—9.4%
	Cambodia—0.9%
	NagaCorp, Ltd. (Hotels, restaurants & leisure)		2,288,000		2,815
	China—4.7%
	Huazhu Group, Ltd.-ADR (Hotels, restaurants & leisure)		93,539		3,391
*	Kingsoft Corporation, Ltd. (Software)		439,000		950
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		3,061,500		7,219
	Silergy Corporation (Semiconductors & semiconductor equipment)		88,000		1,722
	Travelsky Technology, Ltd. Class “H” (IT services)		546,000		1,097
					14,379
	India—0.6%
	Crompton Greaves Consumer Electricals, Ltd. (Household durables)		566,648		1,912

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	Philippines—0.3%
	Jollibee Foods Corporation (Hotels, restaurants & leisure)		193,100	$	1,062
	Taiwan—2.0%
	Chailease Holding Co., Ltd. (Diversified financial services)		357,200		1,478
	Eclat Textile Co., Ltd. (Textiles, apparel & luxury goods)		212,000		2,717
	Feng TAY Enterprise Co., Ltd. (Textiles, apparel & luxury goods)		258,000		2,010
					6,205
	Thailand—0.9%
	Tisco Financial Group PCL (Banks)		901,200		2,748
	Emerging Latin America—5.7%
	Argentina—2.1%
*	Globant S.A. (Software)†		64,511		6,519
	Brazil—2.0%
	CVC Brasil Operadora e Agencia de Viagens S.A. (Hotels, restaurants & leisure)		144,400		1,873
	Localiza Rent a Car S.A. (Road & rail)		403,885		4,310
					6,183
	Mexico—1.6%
	Grupo Aeroportuario del Centro Norte S.A.B. de C.V. (Transportation infrastructure)		307,300		1,878
	Grupo Aeroportuario del Sureste S.A.B. de C.V.—ADR (Transportation infrastructure)		18,288		2,964
					4,842
	Asia—5.1%
	Australia—1.9%
	Corporate Travel Management, Ltd. (Hotels, restaurants & leisure)		114,960		1,816
	Orora, Ltd. (Containers & packaging)		1,340,548		3,049
	SmartGroup Corporation, Ltd. (Commercial services & supplies)		184,753		1,082
					5,947
	Hong Kong—0.7%
	MGM China Holdings, Ltd. (Hotels, restaurants & leisure)		1,169,200		1,988
	New Zealand—2.5%
	Fisher & Paykel Healthcare Corp., Ltd. (Health care equipment & supplies)		220,774		2,293
	Ryman Healthcare, Ltd. (Health care providers & services)		344,553		2,720
	Spark New Zealand, Ltd. (Diversified telecommunication services)		1,039,225		2,792
					7,805

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 65

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

		Shares or
		Principal
	Issuer	Amount		Value
	Common Stocks—(continued)
	Canada—2.7%
	Finning International, Inc. (Trading companies & distributors)		69,888	$	1,274
*	Kinaxis, Inc. (Software)		24,431		1,524
	Parkland Fuel Corporation (Oil, gas & consumable fuels)		80,228		2,545
	The Bank of NT Butterfield & Son, Ltd. (Banks)†		42,324		1,437
	Toromont Industries, Ltd. (Trading companies & distributors)		34,767		1,648
					8,428
	Emerging Europe, Mid-East, Africa—2.5%
	South Africa—2.5%
	AVI, Ltd. (Food products)		405,988		2,633
	Bidvest Group, Ltd. (Industrial conglomerates)		161,274		2,168
	Clicks Group, Ltd. (Food & staples retailing)		199,172		2,903
					7,704
	Total Common Stocks—95.8% (cost $259,885)				295,563
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $13,281, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26	$	13,280		13,280
	Total Repurchase Agreement—4.3% (cost $13,280)				13,280
	Total Investments—100.1% (cost $273,165)				308,843
	Liabilities, plus cash and other assets—(0.1)%				(389	)
	Net assets—100.0%			$	308,454

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Information Technology	20.8	%
Industrials	20.6	%
Consumer Discretionary	17.5	%
Financials	13.2	%
Health Care	10.7	%
Consumer Staples	6.1	%
Real Estate	5.0	%
Materials	2.5	%
Communication Services	1.5	%
Utilities	1.2	%
Energy	0.9	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

British Pound Sterling	19.0	%
Japanese Yen	18.2	%
Euro	17.3	%
Swedish Krona	8.3	%
U.S. Dollar	6.1	%
Hong Kong Dollar	4.8	%
Swiss Franc	3.7	%
Danish Krone	3.3	%
New Taiwan Dollar	2.7	%
New Zealand Dollar	2.6	%
South African Rand	2.6	%
Canadian Dollar	2.4	%
Brazilian Real	2.1	%
Australian Dollar	2.0	%
Israeli Shekel	1.6	%
All Other Currencies	3.3	%
Total	100.0	%

See accompanying Notes to Financial Statements.

66 Semiannual Report June 30, 2019

	Emerging Markets Leaders Fund
	The Emerging Markets Leaders Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Todd M. McClone John C. Murphy	The William Blair Emerging Markets Leaders Fund (Class N shares) posted a 16.71% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets Index (net) (the “Index”) increased 10.58%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. In particular, stock selection in the Financials, Health Care and Communication Services sectors were the most notable contributors to relative return. Within Financials, Ping An Insurance Group Co. of China, Ltd. contributed to relative performance as the company continued to deliver better-than-expected results, driven by strong operating trends and high investment income amid improved equity markets. Jiangsu Hengrui Medicine Co., Ltd., the leading pharmaceutical company in China was an additional source of outperformance. The stock rebounded from policy-driven, sector-wide weakness in the second half of 2018 amid the company’s strong operating momentum and growth outlook, supported by favorable trends in oncology and new product approvals. Within the Communication Services sector, Yandex N.V. helped relative returns on the back of continued strong growth in advertising and an increased contribution from its expanded multi-services platform. Based in Russia, Yandex is Russia’s leading online search engine company that is transitioning beyond its core search business into ventures such as ride-hailing and e-commerce. Partially offsetting these positive effects were underweight allocations to Russia and the Health Care sector, coupled with below average stock selection within the Energy sector. Within Energy, the Fund’s lack of exposure to Russian Energy companies and the Fund’s position in the Australian company Oil Search, Ltd. detracted from relative results. Oil Search was dragged down by market concerns about political instability in Papua New Guinea. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

June 30, 2019 William Blair Funds 67

Emerging Markets Leaders Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception
Class N(a)		16.71	%		3.20	%		9.74	%		2.56	%		—			3.50	%
MSCI Emerging Markets Index (net)(a)		10.58			1.21			10.66			2.49			—			2.97
Class I		16.93			3.52			10.04			2.87			6.78	%		—
Class R6		16.95			3.53			10.08			2.93			6.87			—
MSCI Emerging Markets Index (net)		10.58			1.21			10.66			2.49			5.81			—

(a) Since inception is for the period from May 3, 2010 (Commencement ofOperations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. These risks may be magnified when investing in emerging markets. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) Emerging Markets Index (net) is a free float-adjusted market-capitalization-weighted index that is designed to measure equity market performance of emerging markets. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

68 Semiannual Report June 30, 2019

Emerging Markets Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Emerging Asia—73.1%
	Australia—0.9%
	Oil Search, Ltd. (Oil, gas & consumable fuels)		410,642	$	2,038
	China—33.5%
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		84,534		14,324
	China International Travel Service Corporation, Ltd. Class “A” (Hotels, restaurants & leisure)		373,956		4,827
	CNOOC, Ltd. (Oil, gas & consumable fuels)		2,091,000		3,576
	ENN Energy Holdings, Ltd. (Gas utilities)		293,200		2,852
	Haier Electronics Group Co., Ltd. (Household durables)		1,144,000		3,163
	Huazhu Group, Ltd.—ADR (Hotels, restaurants & leisure)		112,463		4,077
	Jiangsu Hengrui Medicine Co., Ltd. Class “A” (Pharmaceuticals)		218,192		2,097
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		40,859		5,854
	NetEase, Inc.—ADR (Entertainment)		9,920		2,537
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		654,000		7,853
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		276,200		3,797
*	TAL Education Group—ADR (Diversified consumer services)		66,961		2,551
	Tencent Holdings, Ltd. (Interactive Media & Services)		298,900		13,492
*	Tencent Music Entertainment Group—ADR (Entertainment)		266,765		3,999
					74,999
	India—17.8%
	Asian Paints, Ltd. (Chemicals)		100,352		1,976
	Bajaj Finance, Ltd. (Consumer finance)		76,669		4,093
	Britannia Industries, Ltd. (Food products)		44,127		1,756
	HDFC Bank, Ltd. (Banks)		107,977		3,818
	HDFC Bank, Ltd.—ADR (Banks)		7,422		965
	HDFC Life Insurance Co. Ltd.—144A (Insurance)		335,682		2,259
	Hindustan Unilever, Ltd. (Household products)		70,235		1,820
	Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		134,968		4,291
	IndusInd Bank, Ltd. (Banks)		142,671		2,935
	Infosys, Ltd. (IT services)		403,301		4,275
	Maruti Suzuki India, Ltd. (Automobiles)		17,881		1,694
	Motherson Sumi Systems, Ltd. (Auto components)		902,481		1,597
	MRF, Ltd. (Auto components)		3,219		2,648
	Petronet LNG, Ltd. (Oil, gas & consumable fuels)		677,429		2,414
	UPL, Ltd. (Chemicals)		247,189		3,370
					39,911

Issuer	Shares		Value
Common Stocks—(continued)
Emerging Asia—(continued)
Indonesia—5.2%
PT Bank Rakyat Indonesia Persero Tbk (Banks)		16,294,300	$	5,029
PT Telekomunikasi Indonesia Persero Tbk (Diversified telecommunication services)		14,317,800		4,196
PT Unilever Indonesia Tbk (Household products)		742,500		2,365
				11,590
South Korea—3.6%
LG Household & Health Care, Ltd. (Personal products)		2,345		2,667
Samsung Electronics Co., Ltd. (Technology hardware, storage & peripherals)		131,611		5,357
				8,024
Taiwan—8.5%
E.Sun Financial Holding Co., Ltd. (Banks)		2,822,000		2,362
Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		320,832		12,567
Uni-President Enterprises Corporation (Food products)		1,558,000		4,149
				19,078
Thailand—3.6%
Airports of Thailand PCL (Transportation infrastructure)		1,865,800		4,471
CP ALL PCL (Food & staples retailing)		1,327,900		3,724
				8,195
Emerging Latin America—12.9%
Brazil—7.6%
AMBEV S.A.—ADR (Beverages)		543,223		2,537
B3 S.A. - Brasil Bolsa Balcao (Capital markets)		385,600		3,762
IRB Brasil Resseguros S.A. (Insurance)		156,400		4,012
Odontoprev S.A. (Health care providers & services)		94,753		450
Raia Drogasil S.A. (Food & staples retailing)		182,400		3,615
WEG S.A. (Machinery)		451,800		2,513
				16,889
Mexico—3.5%
Grupo Aeroportuario del Pacifico S.A.B. de C.V. Class “B” (Transportation infrastructure)		310,900		3,238
Grupo Financiero Banorte S.A.B. de C.V. Class “O” (Banks)		468,000		2,718
Wal-Mart de Mexico S.A.B. de C.V. (Food & staples retailing)		721,000		1,968
				7,924
Peru—1.8%
Credicorp, Ltd. (Banks)†		17,905		4,099

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 69

Emerging Markets Leaders Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

		Shares or
		Principal
	Issuer	Amount		Value
	Common Stocks—(continued)
	Emerging Europe, Mid-East, Africa—9.7%
	Russia—1.6%
*	Yandex N.V. Class “A” (Interactive Media & Services)†		91,856	$	3,490
	South Africa—8.1%
	Bid Corporation, Ltd. (Food & staples retailing)		89,859		1,958
	Capitec Bank Holdings, Ltd. (Banks)		39,831		3,673
	Clicks Group, Ltd. (Food & staples retailing)		163,502		2,383
	FirstRand, Ltd. (Diversified financial services)		573,447		2,791
	Naspers, Ltd. (Media)		22,476		5,457
	The Bidvest Group, Ltd. (Industrial conglomerates)		136,253		1,832
					18,094
	Total Common Stocks—95.7% (cost $183,319)				214,331
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $9,084, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$9,083	$	9,083
	Total Repurchase Agreement—4.0% (cost $9,083)				9,083
	Total Investments—99.7% (cost $192,402)				223,414
	Cash and other assets, less liabilities—0.3%				649
	Net assets—100.0%			$	224,063

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Financials	25.6	%
Consumer Discretionary	20.6	%
Consumer Staples	16.2	%
Communication Services	12.9	%
Information Technology	10.4	%
Industrials	5.6	%
Energy	3.7	%
Materials	2.5	%
Utilities	1.3	%
Health Care	1.2	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

U.S. Dollar	23.9	%
Indian Rupee	18.2	%
Hong Kong Dollar	16.2	%
South African Rand	8.4	%
Brazilian Real	6.7	%
Yuan Renminbi	6.0	%
Indonesian Rupiah	5.4	%
Thai Baht	3.8	%
South Korean Won	3.7	%
Mexican Peso	3.7	%
New Taiwan Dollar	3.0	%
All Other Currencies	1.0	%
Total	100.0	%

See accompanying Notes to Financial Statements.

70 Semiannual Report June 30, 2019

	Emerging Markets Growth Fund
	The Emerging Markets Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Todd M. McClone Casey K. Preyss	The William Blair Emerging Markets Growth Fund (Class N shares) posted a 15.80% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets IMI (net) (the “Index”), increased 10.14%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. Financials and Industrials were the most notable sources of the Fund’s relative return. Within the Financials sector, Chinese holdings Ping An Insurance Group Co. of China, Ltd. and China Merchants Bank Co., Ltd. bolstered relative returns. Ping An Insurance continued to deliver better-than-expected results, with net profit growth of 77% year-over-year, driven by strong growth across business segments and high investment income amid improved equity markets. Shares of China Merchants Bank, the leading private retail bank in China, continued to climb amid an improved macro backdrop and solid fundamental results. The bank’s growth and profitability continue to stand out relative to large peers. Within Industrials, Shanghai International Airport Co., Ltd., the owner and operator of the third busiest airport in China, was an additional source of outperformance amid solid first quarter results driven by a newly implemented higher duty-free revenue sharing agreement. Partially offsetting these effects was the underweight allocation to the Information Technology sector, coupled with negative stock selection within the Energy and Real Estate sectors. Within Energy, the lack of exposure to Russian Energy, which outperformed on higher crude oil prices, and the position in Reliance Industries Limited, which pared gains from prior quarters, hampered relative results. Multiplan Empreendimentos Imobiliarios S.A., a premier mall operator in Brazil, within the Real Estate sector, was a drag amid weaker first quarter results driven by higher than expected financial expenses and slower operational momentum. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

June 30, 2019 William Blair Funds 71

Emerging Markets Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019

	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		15.80	%		(2.03	)%		9.20	%		2.27	%		6.94	%
Class I		15.91			(1.77	)		9.47			2.52			7.22
Class R6		15.95			(1.70	)		9.58			2.62			7.38
MSCI Emerging Markets IMI (net)		10.14			0.47			10.01			2.25			5.83

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. These risks may be magnified when investing in emerging markets. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) Emerging Markets Investable Market Index (IMI) (net) is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of emerging markets. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

72 Semiannual Report June 30, 2019

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Emerging Asia—71.0%
	China—31.5%
	Aier Eye Hospital Group Co., Ltd. Class “A” (Health care providers & services)		672,920	$	3,034
*	Alibaba Group Holding, Ltd.—ADR (Internet & direct marketing retail)		291,055		49,319
	ANTA Sports Products, Ltd. (Textiles, apparel & luxury goods)		878,000		6,030
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		1,602,400		2,520
	China International Travel Service Corporation, Ltd. Class “A” (Hotels, restaurants & leisure)		704,240		9,090
*	China Mengniu Dairy Co., Ltd. (Food products)		1,499,000		5,805
	China Merchants Bank Co., Ltd. Class “H” (Banks)		3,934,500		19,618
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		1,302,000		3,010
*	Ctrip.com International, Ltd.—ADR (Internet & direct marketing retail)		129,564		4,782
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		566,216		8,656
	Huazhu Group, Ltd.—ADR (Hotels, restaurants & leisure)		82,156		2,978
	Kingdee International Software Group Co., Ltd. (Software)		2,610,000		2,823
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		59,442		8,516
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		1,622,000		3,825
	Midea Group Co., Ltd. Class “A” (Household durables)		512,576		3,870
	NetEase, Inc.—ADR (Entertainment)		14,322		3,663
*	New Oriental Education & Technology Group, Inc.—ADR (Diversified consumer services)		64,966		6,274
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		2,458,000		29,515
	Shanghai International Airport Co., Ltd. Class “A” (Transportation infrastructure)		571,865		6,976
	Shenzhen Mindray Bio-Medical Electronics Co., Ltd. Class “A” (Health care equipment & supplies)		109,000		2,590
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		465,000		6,393
	Silergy Corporation (Semiconductors & semiconductor equipment)		24,000		470
	Tencent Holdings, Ltd. (Interactive Media & Services)		809,460		36,537
	Wuliangye Yibin Co., Ltd. Class “A” (Beverages)		506,294		8,695
*	Wuxi Biologics Cayman, Inc. (Life sciences tools & services)		269,000		2,416
*	Yihai International Holding, Ltd. (Food products)		594,000		3,083

Issuer	Shares		Value
Common Stocks—(continued)
Emerging Asia—(continued)
China—(continued)
Yum China Holdings, Inc. (Hotels, restaurants & leisure)		140,898	$	6,510
Zhejiang Supor Co., Ltd. Class “A” (Household durables)		546,282		6,031
				253,029
India—18.3%
Asian Paints, Ltd. (Chemicals)		243,801		4,800
Bajaj Finance, Ltd. (Consumer finance)		310,066		16,554
Havells India, Ltd. (Electrical equipment)		350,134		3,974
HDFC Asset Management Co., Ltd. (Capital markets)		93,754		2,799
HDFC Bank, Ltd. (Banks)		766,016		27,088
HDFC Life Insurance Co. Ltd. (Insurance)		594,796		4,003
Hindustan Unilever, Ltd. (Household products)		213,589		5,535
Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		536,341		17,050
Indraprastha Gas, Ltd. (Gas utilities)		546,120		2,491
Info Edge India, Ltd. (Interactive Media & Services)		85,861		2,796
Infosys, Ltd. (IT services)		790,795		8,383
Nestle India, Ltd. (Food products)		18,802		3,249
Pidilite Industries, Ltd. (Chemicals)		146,463		2,580
PVR, Ltd. (Entertainment)		93,239		2,259
Reliance Industries, Ltd. (Oil, gas & consumable fuels)		986,029		17,913
SRF, Ltd. (Chemicals)		28,899		1,274
Tata Consultancy Services, Ltd. (IT services)		385,201		12,433
Titan Co., Ltd. (Textiles, apparel & luxury goods)		320,729		6,186
UPL, Ltd. (Chemicals)		387,731		5,286
				146,653
Indonesia—3.4%
PT Bank Central Asia Tbk (Banks)		7,592,300		16,109
PT Bank Rakyat Indonesia Persero Tbk (Banks)		35,625,605		10,995
PT Gudang Garam Tbk (Tobacco)		26,000		141
				27,245
Philippines—0.8%
Ayala Land, Inc. (Real estate management & development)		4,465,300		4,428
Jollibee Foods Corporation (Hotels, restaurants & leisure)		344,040		1,892
				6,320
South Korea—4.3%
Douzone Bizon Co., Ltd. (Software)		39,719		2,140
Fila Korea, Ltd. (Textiles, apparel & luxury goods)		63,680		4,230
Korea Investment Holdings Co., Ltd. (Capital markets)		24,636		1,722
LG Household & Health Care, Ltd. (Personal products)		8,464		9,625

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 73

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks (continued)
	Emerging Asia—(continued)
	South Korea—(continued)
	Macquarie Korea Infrastructure Fund (Capital markets)		293,179	$	2,996
	Samsung Electronics Co., Ltd. (Technology hardware, storage & peripherals)		329,477		13,411
					34,124
	Taiwan—8.2%
	Airtac International Group (Machinery)		149,000		1,669
	Bizlink Holding, Inc. (Electrical equipment)		21,000		145
	Chailease Holding Co., Ltd. (Diversified financial services)		870,380		3,601
	E.Sun Financial Holding Co., Ltd. (Banks)		10,535,171		8,819
	Eclat Textile Co., Ltd. (Textiles, apparel & luxury goods)		196,000		2,512
	Feng TAY Enterprise Co., Ltd. (Textiles, apparel & luxury goods)		381,000		2,968
	Giant Manufacturing Co., Ltd. (Leisure products)		290,000		2,269
	ITEQ Corporation (Electronic equipment, instruments & components)		593,000		2,081
	Makalot Industrial Co., Ltd. (Textiles, apparel & luxury goods)		433,000		2,928
	Parade Technologies, Ltd. (Semiconductors & semiconductor equipment)		115,000		1,955
	Sinbon Electronics Co., Ltd. (Electronic equipment, instruments & components)		115,000		420
	Taiwan Semiconductor Manufacturing Co., Ltd. (Semiconductors & semiconductor equipment)		1,830,000		14,082
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		455,675		17,849
	Taiwan Union Technology Corporation (Electronic equipment, instruments & components)		471,000		1,888
	Tripod Technology Corporation (Electronic equipment, instruments & components)		631,000		2,235
					65,421
	Thailand—4.1%
	Airports of Thailand PCL (Transportation infrastructure)		2,207,500		5,291
	Bangkok Dusit Medical Services PCL Class “F” (Health care providers & services)		4,947,800		4,195
	Bangkok Expressway & Metro PCL (Transportation infrastructure)		7,450,500		2,769
	CP ALL PCL (Food & staples retailing)		3,018,300		8,464
	Home Product Center PCL (Specialty retail)		6,502,300		3,710
	Muangthai Capital PCL (Consumer finance)		1,154,900		2,128
*	Sea, Ltd.—ADR (Entertainment)		189,887		6,308
					32,865

	Issuer	Shares		Value
	Common Stocks (continued)
	Emerging Asia—(continued)
	Vietnam—0.4%
	Vietjet Aviation JSC (Airlines)		4	$	—@
	Vincom Retail JSC (Real estate management & development)		1,076,801		1,561
*	Vingroup JSC (Real estate management & development)		388,498		1,929
					3,490
	Emerging Latin America—15.9%
	Argentina—2.0%
*	Globant S.A. (Software)†		46,658		4,715
*	MercadoLibre, Inc. (Interactive Media & Services)		18,252		11,166
					15,881
	Brazil—10.1%
	B3 S.A.-Brasil Bolsa Balcao (Capital markets)		1,404,900		13,705
	Banco BTG Pactual S.A. (Capital markets)		313,600		4,155
	BK Brasil Operacao e Assessoria a Restaurantes S.A. (Hotels, restaurants & leisure)		337,900		1,957
	Cyrela Brazil Realty SA Empreendimentos e Participacoes (Household durables)		526,000		2,849
	Energisa S.A. (Electric utilities)		246,975		2,964
	Engie Brasil Energia S.A. (Independent power & renewable electricity producers)		277,150		3,138
	IRB Brasil Resseguros S.A. (Insurance)		305,000		7,824
	Localiza Rent a Car S.A. (Road & rail)		944,220		10,077
	Lojas Renner S.A. (Multiline retail)		943,280		11,585
	Magazine Luiza S.A. (Multiline retail)		89,200		4,904
	Notre Dame Intermedica Participacoes S.A. (Health care providers & services)		250,500		2,630
	Odontoprev S.A. (Health care providers & services)		415,200		1,974
*	Rumo S.A. (Road & rail)		716,900		3,870
	Sul America S.A. (Insurance)		256,400		2,505
	TOTVS S.A. (Software)		237,400		2,719
	WEG S.A. (Machinery)		793,120		4,412
					81,268
	Chile—0.3%
	Banco Santander Chile—ADR (Banks)		80,807		2,418
	Colombia—0.3%
	Bancolombia S.A.—ADR (Banks)		46,778		2,387
	Mexico—2.2%
	Grupo Aeroportuario del Centro Norte S.A.B. de C.V. (Transportation infrastructure)		306,400		1,873
	Grupo Aeroportuario del Sureste S.A.B. de C.V.—ADR (Transportation infrastructure)		9,994		1,620

See accompanying Notes to Financial Statements.

74 Semiannual Report June 30, 2019

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Latin America—(continued)
	Mexico—(continued)
	Grupo Financiero Banorte S.A.B. de C.V. Class “O” (Banks)		1,065,600	$	6,189
	Wal-Mart de Mexico S.A.B. de C.V. (Food & staples retailing)		2,933,500		8,007
					17,689
	Peru—1.0%
	Credicorp, Ltd. (Banks)†		35,431		8,110
	Emerging Europe, Mid-East, Africa—9.5%
	Czech Republic—0.3%
	Moneta Money Bank A.S. (Banks)		699,893		2,398
	Greece—0.3%
	JUMBO S.A. (Specialty retail)		132,432		2,560
	Hungary—1.2%
	OTP Bank Nyrt (Banks)		243,586		9,688
	Kenya—0.3%
	Safaricom plc (Wireless telecommunication services)		7,648,554		2,088
	Poland—0.7%
	CD Projekt S.A. (Entertainment)		50,101		2,889
*	Dino Polska S.A. (Food & staples retailing)		78,948		2,768
					5,657
	Romania—0.3%
	Banca Transilvania S.A. (Banks)		4,144,906		2,389
	Russia—0.9%
	TCS Group Holding plc—GDR (Banks)		91,000		1,784
*	Yandex N.V. Class “A” (Interactive Media & Services)†		150,022		5,701
					7,485
	South Africa—4.1%
	Bidvest Group, Ltd. (Industrial conglomerates)		135,760		1,825
	Capitec Bank Holdings, Ltd. (Banks)		75,177		6,932
	Clicks Group, Ltd. (Food & staples retailing)		255,447		3,723
	FirstRand, Ltd. (Diversified financial services)		811,309		3,948
	Naspers, Ltd. (Media)		69,029		16,759
					33,187
	United Arab Emirates—1.4%
	Aramex PJSC (Air freight & logistics)		1,467,823		1,658
	First Abu Dhabi Bank PJSC (Banks)		1,309,262		5,297
*	Network International Holdings plc (IT services)		519,419		3,912
					10,867
	Total Common Stocks—96.4% (cost $627,532)				773,219

	Shares or
	Principal
Issuer	Amount		Value
Preferred Stock
Brazil—1.7%
Itau Unibanco Holding S.A. (Banks)		1,444,990	$	13,645
Total Preferred Stock—1.7% (cost $13,838)				13,645
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $14,764, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$14,763	$	14,763
Total Repurchase Agreement—1.8% (cost $14,763)				14,763
Total Investments—99.9% (cost $656,133)				801,627
Cash and other assets, less liabilities—0.1%				703
Net assets—100.0%			$	802,330

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

@ = Value is less than the minimum amount disclosed.

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 75

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2019(unaudited)

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Financials	32.6	%
Consumer Discretionary	23.3	%
Information Technology	11.6	%
Consumer Staples	9.7	%
Communication Services	7.9	%
Industrials	6.6	%
Energy	2.3	%
Health Care	2.1	%
Materials	1.8	%
Utilities	1.1	%
Real Estate	1.0	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Indian Rupee	18.6	%
U.S. Dollar	17.2	%
Hong Kong Dollar	15.1	%
Brazilian Real	12.1	%
Yuan Renminbi	7.6	%
New Taiwan Dollar	6.1	%
South Korean Won	4.3	%
South African Rand	4.2	%
Indonesian Rupiah	3.5	%
Thai Baht	3.4	%
Mexican Peso	2.1	%
Hungarian Forint	1.2	%
All Other Currencies	4.6	%
Total	100.0	%

See accompanying Notes to Financial Statements.

76 Semiannual Report June 30, 2019

	Emerging Markets Small Cap Growth Fund
	The Emerging Markets Small Cap Growth Fund seeks long-term capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Todd M. McClone Casey K. Preyss	The William Blair Emerging Markets Small Cap Growth Fund (Class N shares) posted an 8.88% increase, net of fees, for the six months ended June 30, 2019. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets Small Cap Index (net) (the “Index”), increased 6.70%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. Stock selection within the Industrials sector was particularly positive, enhanced by Centre Testing International Group Co., Ltd. and Localiza Rent a Car S.A. . Centre Testing International is a leading testing, inspection and certification company in a highly fragmented market. The stock price accelerated on the back of the company’s strong operating momentum amid solid sales growth across all business segments and management’s increased focus on profitability, which led to impressive gross margin growth. The share price of Brazilian rental car company Localiza Rent a Car strengthened due to the company’s robust operating performance and positive growth outlook amid an improved macro backdrop in Brazil, continued industry consolidation, and efficiency gains. Partially offsetting these positive effects was negative stock selection within the Utilities and Materials sectors. Within Utilities, Mahanagar Gas, Ltd. hampered relative returns, due to disappointing results from the fourth quarter of 2019. Within Materials, Posco Chemical Co., Ltd., a Korean-based leading producer of carbon-based battery anode and other advanced materials, detracted from relative performance as weaker needle coke prices weighed on the stock. Needle coke is a key raw material for electric steel-making equipment, which Posco Chemical is heavily reliant upon. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 32 for additional information.

June 30, 2019 William Blair Funds 77

Emerging Markets Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019

	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		8.88	%		(8.06	)%		3.04	%		1.24	%		7.92	%
Class I(a)		8.97			(7.81	)		3.36			1.54			8.23
MSCI Emerging Markets Small Cap Index (net)(a)		6.70			(5.12	)		5.46			0.53			3.41
Class R6(b)		9.03			(7.75	)		3.42			1.62			5.66
MSCI Emerging Markets Small Cap Index (net)(b)		6.70			(5.12	)		5.46			0.53			2.12

(a)	Since inception is for the period from October 24, 2011 (Commencement of Operations) to June 30, 2019.
(b)	Since inception is for the period from December 20, 2012 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. International investing involves special risk considerations, including currency fluctuations, lower liquidity, economic and political risk. These risks may be magnified when investing in emerging markets. Smaller capitalization stocks are also more sensitive to purchase/sale transactions and changes in the issuer’s financial condition. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Morgan Stanley Capital International (MSCI) Emerging Markets Small Cap Index (net) is a free float-adjusted market capitalization index that is designed to measure the equity market performance of emerging markets. This index approximates the minimum possible dividend reinvestment by deducting for the highest possible withholding tax rates of those markets.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all stocks in the Fund performed the same, nor is there any guarantee that these stocks will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total long-term securities.

78 Semiannual Report June 30, 2019

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks
	Emerging Asia—75.4%
	Cambodia—0.7%
	NagaCorp, Ltd. (Hotels, restaurants & leisure)		1,578,000	$	1,941
	China—20.5%
	A-Living Services Co. Ltd. Class “H” (Commercial services & supplies)		1,071,250		1,810
	Anhui Gujing Distillery Co., Ltd. Class “A” (Beverages)		73,700		1,272
*	Ausnutria Dairy Corporation, Ltd. (Food products)		44,000		88
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		1,214,105		1,909
	China Education Group Holdings, Ltd. (Diversified consumer services)		2,291,000		3,578
	China Suntien Green Energy Corporation, Ltd. Class “H” (Oil, gas & consumable fuels)		7,344,000		1,955
	China Water Affairs Group, Ltd. (Water utilities)		1,460,000		1,437
	CIFI Holdings Group Co., Ltd. (Real estate management & development)		1,660,000		1,094
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		1,045,000		2,416
*	GSX Techedu, Inc.—ADR (Diversified consumer services)		85,359		921
	Guangdong Haid Group Co., Ltd. Class “A” (Food products)		516,204		2,322
	Hangzhou Tigermed Consulting Co., Ltd. Class “A” (Life sciences tools & services)		100,000		1,123
	Hua Hong Semiconductor Ltd. (Semiconductors & semiconductor equipment)		486,600		942
	Jiangsu Hengli Hydraulic Co., Ltd. Class “A” (Machinery)		267,466		1,222
	Jiangsu Hengshun Vinegar Industry Co., Ltd. Class “A” (Food products)		669,500		1,796
	JNBY Design, Ltd. (Textiles, apparel & luxury goods)		906,000		1,661
	Jonjee Hi-Tech Industrial And Commercial Holding Co., Ltd. Class “A” (Food products)		327,529		2,042
	Kingdee International Software Group Co., Ltd. (Software)		1,714,000		1,854
*	Kingsoft Corporation, Ltd. (Software)		563,000		1,218
*	KWG Group Holdings, Ltd. (Real estate management & development)		1,401,000		1,422
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		1,999,000		4,714
	Logan Property Holdings Co., Ltd. (Real estate management & development)		1,060,000		1,715
*	Noah Holdings, Ltd.—ADR (Capital markets)		9,181		391
	Qiaqia Food Co., Ltd. Class “A” (Food products)		535,913		1,970

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	China—(continued)
	Silergy Corporation (Semiconductors & semiconductor equipment)		78,000	$	1,527
	Toly Bread Co., Ltd. Class “A” (Food products)		119,400		724
*	Topchoice Medical Investment Corporation Class “A” (Health care providers & services)		122,700		1,583
	TravelSky Technology, Ltd. Class “H” (IT services)		235,000		472
	Venustech Group, Inc. Class “A” (Software)		226,383		887
	Vitasoy International Holdings, Ltd. (Food products)		382,000		1,836
	Xtep International Holdings, Ltd. (Textiles, apparel & luxury goods)		1,369,000		825
*	Yihai International Holding, Ltd. (Food products)		749,000		3,888
	Zhejiang Dingli Machinery Co., Ltd. Class “A” (Machinery)		175,654		1,502
	Zhejiang Supor Co., Ltd. Class “A” (Household durables)		223,308		2,465
	Zhejiang Weixing New Building Materials Co., Ltd. Class “A” (Building products)		525,976		1,333
					57,914
	India—22.6%
	Aarti Industries, Ltd. (Chemicals)		138,963		3,577
	Astral Poly Technik, Ltd. (Building products)		219,534		4,214
	Bandhan Bank Ltd. (Banks)		196,962		1,541
	Bata India, Ltd. (Textiles, apparel & luxury goods)		132,730		2,776
	Berger Paints India, Ltd. (Chemicals)		354,377		1,632
	City Union Bank, Ltd. (Banks)		716,507		2,263
	Endurance Technologies Ltd. (Auto components)		82,048		1,311
*	Gruh Finance, Ltd. (Thrifts & mortgage finance)		717,244		2,893
	Havells India, Ltd. (Electrical equipment)		338,718		3,845
	HDFC Asset Management Co. Ltd. (Capital markets)		45,106		1,347
	Indraprastha Gas, Ltd. (Gas utilities)		387,115		1,766
	Info Edge India, Ltd. (Interactive Media & Services)		121,472		3,956
	Ipca Laboratories, Ltd. (Pharmaceuticals)		169,619		2,265
	Jubilant Foodworks, Ltd. (Hotels, restaurants & leisure)		72,809		1,300
	Kajaria Ceramics, Ltd. (Building products)		182,433		1,538
	KEI Industries, Ltd. (Electrical equipment)		143,933		1,001
	Larsen & Toubro Infotech Ltd. (IT services)		35,531		949

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 79

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	India—(continued)
	Mahanagar Gas, Ltd. (Gas utilities)		126,266	$	1,557
	NIIT Technologies, Ltd. (IT services)		115,022		2,241
	Oberoi Realty, Ltd. (Real estate management & development)		106,412		931
	PI Industries, Ltd. (Chemicals)		73,965		1,258
	Pidilite Industries, Ltd. (Chemicals)		144,477		2,545
	PVR, Ltd. (Entertainment)		117,660		2,850
	RBL Bank Ltd. (Banks)		213,730		1,988
	SRF, Ltd. (Chemicals)		65,973		2,908
	Sundram Fasteners, Ltd. (Auto components)		117,014		866
	Titan Co., Ltd. (Textiles, apparel & luxury goods)		282,923		5,457
	V-Mart Retail, Ltd. (Multiline retail)		33,702		1,076
	Varun Beverages, Ltd. (Beverages)		128,738		1,762
					63,613
	Indonesia—4.0%
	PT Ace Hardware Indonesia Tbk (Specialty retail)		38,995,000		4,996
*	PT Bank Tabungan Pensiunan Nasional Syariah Tbk (Banks)		8,533,400		2,084
	PT Gudang Garam Tbk (Tobacco)		19,900		108
	PT Media Nusantara Citra Tbk (Media)		11,106,900		818
	PT Pakuwon Jati Tbk (Real estate management & development)		62,172,500		3,213
					11,219
	Philippines—4.0%
	Bloomberry Resorts Corporation (Hotels, restaurants & leisure)		10,471,300		2,309
	International Container Terminal Services, Inc. (Transportation infrastructure)		1,166,630		3,334
	Jollibee Foods Corporation (Hotels, restaurants & leisure)		345,940		1,903
	Security Bank Corporation (Banks)		635,640		2,109
	Wilcon Depot, Inc. (Specialty retail)		4,956,500		1,625
					11,280
	South Korea—5.6%
	Dentium Co., Ltd. (Health care equipment & supplies)		11,512		733
	Douzone Bizon Co., Ltd. (Software)		55,190		2,973
	Fila Korea, Ltd. (Textiles, apparel & luxury goods)		48,557		3,226
	JYP Entertainment Corporation (Entertainment)		97,243		2,013
	Koh Young Technology, Inc. (Semiconductors & semiconductor equipment)		42,453		3,055
	Korea Investment Holdings Co., Ltd. (Capital markets)		23,844		1,666
	Macquarie Korea Infrastructure Fund (Capital markets)		201,593		2,060
					15,726

Issuer	Shares		Value
Common Stocks—(continued)
Emerging Asia—(continued)
Taiwan—14.8%
Airtac International Group (Machinery)		206,000	$	2,308
ASMedia Technology, Inc. (Semiconductors & semiconductor equipment)		122,000		1,901
ASPEED Technology, Inc. (Semiconductors & semiconductor equipment)		71,000		1,353
Bizlink Holding, Inc. (Electrical equipment)		285,000		1,973
Chailease Holding Co., Ltd. (Diversified financial services)		292,000		1,208
Chroma ATE, Inc. (Electronic equipment, instruments & components)		507,000		2,253
Eclat Textile Co., Ltd. (Textiles, apparel & luxury goods)		43,000		551
Feng TAY Enterprise Co., Ltd. (Textiles, apparel & luxury goods)		440,000		3,428
Giant Manufacturing Co., Ltd. (Leisure products)		201,000		1,573
Globalwafers Co., Ltd. (Semiconductors & semiconductor equipment)		130,000		1,316
ITEQ Corporation (Electronic equipment, instruments & components)		515,000		1,807
King Yuan Electronics Co., Ltd. (Semiconductors & semiconductor equipment)		1,293,000		1,116
Land Mark Optoelectronics Corporation (Semiconductors & semiconductor equipment)		114,000		960
Makalot Industrial Co., Ltd. (Textiles, apparel & luxury goods)		488,000		3,300
Nanya Technology Corporation (Semiconductors & semiconductor equipment)		357,000		741
Parade Technologies, Ltd. (Semiconductors & semiconductor equipment)		221,000		3,757
Sinbon Electronics Co., Ltd. (Electronic equipment, instruments & components)		962,000		3,515
Sporton International, Inc. (Professional services)		210,000		1,241
Taiwan Paiho, Ltd. (Textiles, apparel & luxury goods)		530,000		1,531
Taiwan Union Technology Corporation (Electronic equipment, instruments & components)		511,000		2,048
Tripod Technology Corporation (Electronic equipment, instruments & components)		432,000		1,530
Voltronic Power Technology Corporation (Electrical equipment)		105,000		2,289
				41,699
Thailand—3.2%
Bangkok Expressway & Metro PCL (Transportation infrastructure)		6,046,100		2,247

See accompanying Notes to Financial Statements.

80 Semiannual Report June 30, 2019

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Issuer	Shares		Value
	Common Stocks—(continued)
	Emerging Asia—(continued)
	Thailand—(continued)
	Home Product Center PCL (Specialty retail)		4,783,400	$	2,730
	Muangthai Capital PCL (Consumer finance)		1,066,700		1,965
	Tisco Financial Group PCL (Banks)		725,500		2,212
					9,154
	Emerging Latin America—14.1%
	Argentina—1.3%
*	Globant S.A. (Software)†		37,623		3,802
	Brazil—12.8%
*	Azul S.A.—ADR (Airlines)		14,400		482
	BK Brasil Operacao e Assessoria a Restaurantes S.A. (Hotels, restaurants & leisure)		475,200		2,752
	Construtora Tenda S.A. (Household durables)		522,372		3,251
	Cyrela Brazil Realty SA Empreendimentos e Participacoes (Household durables)		605,600		3,280
	IRB Brasil Resseguros S.A. (Insurance)		129,700		3,327
	Localiza Rent a Car S.A. (Road & rail)		348,995		3,725
	Magazine Luiza S.A. (Multiline retail)		58,300		3,205
	MRV Engenharia e Participacoes S.A. (Household durables)		297,400		1,516
	Multiplan Empreendimentos Imobiliarios S.A. (Real estate management & development)		272,200		1,968
	Notre Dame Intermedica Participacoes S.A. (Health care providers & services)		418,500		4,394
	OdontoPrev S.A. (Health care providers & services)		523,100		2,488
	Sul America S.A. (Insurance)		90,000		879
	Tegma Gestao Logistica S.A. (Road & rail)		331,700		2,483
	TOTVS S.A. (Software)		210,100		2,406
					36,156
	Emerging Europe, Mid-East, Africa—7.9%
	Greece—0.2%
	JUMBO S.A. (Specialty retail)		25,696		497
	Kenya—0.4%
	Safaricom, Ltd. (Wireless telecommunication services)		3,974,400		1,085
	Poland—1.6%
	CD Projekt S.A. (Entertainment)		15,191		876
*	Dino Polska S.A. (Food & staples retailing)		101,753		3,567
					4,443

		Shares or
		Principal
	Issuer	Amount		Value
	Common Stocks—(continued)
	Emerging Europe, Mid-East, Africa—(continued)
	Russia—0.5%
	TCS Group Holding plc—GDR (Banks)		74,333	$	1,457
	South Africa—4.0%
	AVI, Ltd. (Food products)		180,074		1,168
	Capitec Bank Holdings, Ltd. (Banks)		34,381		3,170
	Clicks Group, Ltd. (Food & staples retailing)		162,265		2,365
	PSG Group, Ltd. (Diversified financial services)		211,465		3,589
	Santam, Ltd. (Insurance)		53,720		1,144
					11,436
	United Arab Emirates—1.2%
*	Network International Holdings plc (IT services)		446,857		3,365
	Total Common Stocks—97.4% (cost $236,249)				274,787
	Preferred Stock
	Brazil—0.8%
	Randon Participacoes S.A. (Machinery)		908,350		2,138
	Total Preferred Stock—0.8% (cost $1,810)				2,138
	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $224, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		$224		224
	Total Repurchase Agreement—0.1% (cost $224)				224
	Total Investments—98.3% (cost $238,283)				277,149
	Cash and other assets, less liabilities—1.7%				4,843
	Net assets—100.0%			$	281,992

ADR = American Depository Receipt

GDR = Global Depository Receipt

* = Non-income producing security
† = U.S. listed foreign security

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 81

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2019(unaudited)

At June 30, 2019, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Consumer Discretionary	25.6	%
Information Technology	17.3	%
Industrials	15.5	%
Financials	13.5	%
Consumer Staples	9.0	%
Health Care	4.5	%
Materials	4.3	%
Communication Services	4.2	%
Real Estate	3.7	%
Utilities	1.7	%
Energy	0.7	%
Total	100.0	%

At June 30, 2019, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Indian Rupee	23.0	%
New Taiwan Dollar	15.6	%
Brazilian Real	13.7	%
Hong Kong Dollar	12.6	%
Yuan Renminbi	8.0	%
South Korean Won	5.7	%
South African Rand	4.1	%
Philippine Peso	4.1	%
Indonesian Rupiah	4.0	%
Thai Baht	3.3	%
U.S. Dollar	2.5	%
Polish Zloty	1.6	%
British Pound Sterling	1.2	%
All Other Currencies	0.6	%
Total	100.0	%

See accompanying Notes to Financial Statements.

82 Semiannual Report June 30, 2019

Fixed Income Market Review and Outlook

The Bloomberg Barclays U.S. Aggregate Index (the “Index”) returned 3.08% during the second quarter of 2019 and 6.11% for the year-to-date period ending June 30, 2019. It has been a favorable environment for high-quality bonds year-to-date. Interest rates declined throughout the first half of the year, as the 10 Year U.S. Treasury Note’s yield declined by roughly 0.70% year-to-date and traded at levels below 2.00% during June before closing the quarter with a yield of 2.01%. Corporate risk spreads declined during the first quarter of 2019 and changed little during the second quarter.

The Federal Open Market Committee (“FOMC”) made no changes to the target range of the federal funds rate year-to-date. However, the market’s expectations of FOMC activity has changed drastically. The market’s implied expectations indicated a belief that the FOMC would keep the target range of the Federal Funds rate unchanged during 2019, with more market participants protecting against rate hikes during the year than there were market participants protecting against rate cuts. At the end of the second quarter, the market’s implied expectations revealed expectations of two rate cuts during the last six months of 2019 (by 0.25% each time) with an immeasurably low number of market participants protecting against a rate hike. Interest rates on most tenors of U.S. Treasury securities (“Treasuries”) responded by declining to levels below the yield on three-month Treasury bills.

The FOMC also updated its plans regarding the size and composition of its balance sheet. The FOMC had been permitting the balance sheet to reduce by no more than $50 billion per month since October 2017. The FOMC will now permit the balance sheet to reduce by no more than $35 billion per month from May through September 2019 and by no more than $20 billion per month starting in October 2019. The FOMC communicated plans to change the composition of the balance sheet so that it is comprised of primarily Treasuries. The FOMC intends to allow the balance sheet’s agency mortgage-backed securities (“MBS”) to decline at a rate of no more than $20 billion per month, while any cash flows generated in excess of $20 billion per month will be reinvested into Treasuries. The FOMC also stated that “limited sales of agency MBS might be warranted in the longer run to reduce or eliminate residual holdings. The timing and pace of any sales would be communicated to the public well in advance.”

U.S. Treasury Inflation-Protected Securities (“TIPS”) performed in-line with comparable fixed-rate Treasuries year-to-date. Market-implied breakeven inflation rates changed little since the beginning of year, although the implied expectations increased significantly during the first quarter and decreased significantly during the second quarter. The current implied inflation expectations are below the FOMC’s stated objective of 2.0% to 2.5% per year.

Agency MBS outperformed comparable duration U.S. Treasuries year-to-date despite underperforming during the second quarter. The best-performing segments of the market year-to-date were higher-coupon 30-year pools (coupons of 6.0% and 6.5%) and 30-year 3.0% pools that became the production coupon (the coupon of pools given the prevailing level of mortgage rates) amid the declining interest rate environment during the first half of 2019.

Corporate bonds of all tenors, credit qualities, and sectors outperformed similar-maturity Treasury instruments during the second quarter and year-to-date. Longer-maturity corporate bonds outperformed shorter-maturity corporate bonds after adjusting for the effects of duration. Lower-quality segments of the market outperformed higher-quality segments of the market year-to-date. Emerging market corporate bonds also generated strong returns during the first half of 2019.

We believe that the FOMC will be measured in its decisions to decrease the target range of the federal funds rate in 2019. The U.S. economy is growing; forecasters predict a real GDP growth rate of approximately 2.1% during 2019. In addition, the U.S. labor market is adding jobs and the unemployment rate is at 3.7% as of June 30, 2019. Estimates of wage inflation are roughly 3.7%, while estimates of core personal consumption expenditures (“PCE”) are 1.5% as of June 30, 2019. We believe that the FOMC will not cut rates to levels that may spur undesired inflationary pressures.

We believe TIPS are an attractive alternative to fixed-rate Treasuries to mitigate the effects of rising rates driven by accelerating inflationary pressures. We believe that spread sectors remain attractive relative to Treasuries over the intermediate-to-long term. Corporate risk premiums are at levels above their longer-term averages, and we believe there are attractive opportunities in this market. Risk premiums of higher-coupon segments of the agency MBS market remain attractive.

June 30, 2019 William Blair Funds 83

Fixed Income Market Review and Outlook (continued)

We believe that higher-coupon segments (30-year MBS coupon rates of 5.0% and above) of the agency MBS market offer compelling value. In our view, these segments of the agency MBS market offer attractive spreads and a defensive duration profile. The key risk of these securities is that the underlying borrowers are in-the-money to refinance their loan. We believe this risk can be mitigated by focusing on pools comprised of borrowers that do not have the economic incentive to refinance their loans: low-loan balance pools.

We believe that there are opportunities in the corporate bond market. We remain concerned about company-specific risks, including shareholder-friendly activities such as leveraged finance mergers and acquisitions, large share repurchases, and special dividends. Importantly, we do not believe the market will enter a period of excessive leveraged buy-out activity.

84 Semiannual Report June 30, 2019

	Bond Fund
	The Bond Fund seeks to outperform the Bloomberg Barclays U.S. Aggregate Index by maximizing total return through a combination of income and capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Paul J. Sularz Christopher T. Vincent	The William Blair Bond Fund (Class N shares) returned 8.05%, net of fees, for the six month period ended June 30, 2019. By comparison, the Fund’s benchmark, the Bloomberg Barclays U.S. Aggregate Index (the “Index”), returned 6.11%. A couple of factors contributed to the Fund’s performance relative to the Index year-to-date. The Fund’s overweight to longer-maturity investment-grade corporate bonds was additive to performance. Positions that contributed to performance included bonds issued by AT&T, Inc., HSBC Holdings plc, Citigroup, Inc., and Toll Brothers Finance Corporation. The Fund experienced contributions from an allocation to high-yield corporate bonds coupled with favorable selection results, with specific contributions from positions in bonds issued by Navient Corporation, United Rentals North America, Inc., and Penske Automotive Group, Inc. Positioning in corporate bonds issued by companies domiciled in emerging markets also impacted results favorably, as holdings in bonds issued by Petrobras Global Finance B.V. and Mexichem S.A.B. de C.V. were additive. An overweight allocation to higher-coupon segments of the agency mortgage-backed securities market impacted results favorably. There were a couple of factors that detracted from the Fund’s performance relative to the Index year-to-date. Credit risk hedging detracted from the Fund’s results as corporate bonds generated strong returns. Residual cash dragged on performance as bonds experienced gains. Please refer to the Fixed Income Market Review and Outlook relating to the Fund beginning on page 83 for additional information.

June 30, 2019 William Blair Funds 85

Bond Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date		1 Year		3 Year		5 Year		10 Year
Class N	8.05	%	7.89	%	2.74	%	2.80	%	4.62	%
Class I	8.09		7.99		2.94		2.98		4.80
Class R6	8.12		8.05		3.00		3.05		4.91
Bloomberg Barclays U.S. Aggregate Index	6.11		7.87		2.31		2.95		3.90

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Bloomberg Barclays U.S. Aggregate Index indicates broad intermediate government/corporate bond market performance.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all investments in the Fund performed the same, nor is there any guarantee that these investments will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

86 Semiannual Report June 30, 2019

Bond Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Principal Amount		Value
U.S. Government and U.S. Government Agency—51.8%
U.S. Treasury Inflation Indexed Notes/Bonds—6.4%
U.S. Treasury Inflation Indexed Bond, 3.875%, due 4/15/29	$	19,894	$	26,645
U.S. Treasury—0.1%
U.S. Treasury Floating Rate Note, 2.235%, due 4/30/21(a)		500		500
Federal Home Loan Mortgage Corp.(FHLMC)—13.5%
#J02986, 6.500%, due 7/1/21		5		5
#G12720, 5.500%, due 6/1/22		12		12
#D95621, 6.500%, due 7/1/22		257		267
#G14150, 4.500%, due 4/1/26		858		910
#J16051, 4.500%, due 7/1/26		503		536
#G02210, 7.000%, due 12/1/28		43		49
#G02183, 6.500%, due 3/1/30		7		8
#G01400, 7.000%, due 4/1/32		432		502
#G01728, 7.500%, due 7/1/32		73		89
#C01385, 6.500%, due 8/1/32		56		66
#C01623, 5.500%, due 9/1/33		67		74
#A15039, 5.500%, due 10/1/33		2		2
#A17603, 5.500%, due 1/1/34		1,438		1,606
#G01843, 6.000%, due 6/1/35		13		15
#G03711, 6.000%, due 6/1/37		411		472
#G04126, 6.000%, due 6/1/37		1,297		1,491
#A62858, 6.500%, due 7/1/37		71		80
#G03170, 6.500%, due 8/1/37		136		158
#A66843, 6.500%, due 10/1/37		602		718
#G07837, 6.500%, due 2/1/38		1,907		2,263
#G04053, 5.500%, due 3/1/38		552		613
#A78138, 5.500%, due 6/1/38		206		233
#G04641, 6.000%, due 6/1/38		992		1,131
#G04466, 5.500%, due 7/1/38		10,987		12,397
#G04544, 6.000%, due 8/1/38		575		653
#A81799, 6.500%, due 9/1/38		308		343
#G06964, 5.500%, due 11/1/38		1,513		1,699
#G05723, 6.500%, due 11/1/38		878		1,039
#G60366, 6.000%, due 10/1/39		11,406		13,036
#G05875, 5.500%, due 2/1/40		406		453
#G61450, 6.000%, due 4/1/40		11,311		13,013
#G61050, 5.500%, due 3/1/41		418		469
#C03665, 9.000%, due 4/1/41		359		420
#G06583, 5.000%, due 6/1/41		1,225		1,354
Total FHLMC Mortgage Obligations				56,176
Federal National Mortgage Association(FNMA)—31.8%
#900725, 6.000%, due 8/1/21		10		10
#893325, 7.000%, due 9/1/21		3		3
#949589, 5.500%, due 8/1/22		916		943
#949592, 6.000%, due 8/1/22		1,345		1,392
#AC5410, 4.500%, due 10/1/24		183		191
#AL8529, 6.000%, due 11/1/24		2,112		2,202
#AC9560, 5.000%, due 1/1/25		742		773
#255956, 5.500%, due 10/1/25		9		9
#AL2853, 4.500%, due 6/1/26		3,766		4,007
#AL9730, 4.500%, due 2/1/27		1,194		1,270
#AL2134, 4.000%, due 7/1/27		184		194
#AL9857, 4.000%, due 2/1/29		7,176		7,546

Issuer	Principal Amount		Value
U.S. Government and U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#252925, 7.500%, due 12/1/29	$	1	$	1
#AD0729, 7.500%, due 12/1/30		6,721		7,899
#535977, 6.500%, due 4/1/31		5		6
#253907, 7.000%, due 7/1/31		1		1
#545339, 6.500%, due 11/1/31		29		33
#587849, 6.500%, due 11/1/31		7		7
#618547, 6.500%, due 11/1/31		3,576		4,104
#545437, 7.000%, due 2/1/32		34		39
#545759, 6.500%, due 7/1/32		283		327
#545869, 6.500%, due 7/1/32		923		1,065
#670385, 6.500%, due 9/1/32		439		511
#254548, 5.500%, due 12/1/32		28		31
#703391, 5.000%, due 5/1/33		95		104
#708993, 5.000%, due 6/1/33		18		20
#730131, 5.000%, due 8/1/33		45		49
#741850, 5.500%, due 9/1/33		326		362
#555800, 5.500%, due 10/1/33		32		35
#CA2754, 4.500%, due 11/1/33		859		924
#756153, 5.500%, due 11/1/33		363		403
#AL3455, 5.500%, due 11/1/33		4,470		4,994
#AL3401, 5.500%, due 2/1/34		885		989
#763798, 5.500%, due 3/1/34		57		63
#725611, 5.500%, due 6/1/34		70		78
#745563, 5.500%, due 8/1/34		413		459
#794474, 6.000%, due 10/1/34		34		39
#745092, 6.500%, due 7/1/35		223		259
#357944, 6.000%, due 9/1/35		10		12
#AD0979, 7.500%, due 10/1/35		48		56
#745349, 6.500%, due 2/1/36		193		232
#888305, 7.000%, due 3/1/36		7		8
#895637, 6.500%, due 5/1/36		42		48
#831540, 6.000%, due 6/1/36		15		17
#893318, 6.500%, due 8/1/36		8		9
#310037, 6.500%, due 10/1/36		120		143
#831926, 6.000%, due 12/1/36		444		504
#902974, 6.000%, due 12/1/36		116		131
#AB0265, 6.000%, due 2/1/37		9,291		10,680
#938440, 6.000%, due 7/1/37		66		75
#948689, 6.000%, due 8/1/37		106		118
#888703, 6.500%, due 8/1/37		2,880		3,456
#888530, 7.500%, due 8/1/37		817		995
#AL6411, 7.000%, due 12/1/37		1,731		1,984
#AL0904, 5.500%, due 1/1/38		86		96
#889371, 6.000%, due 1/1/38		2,068		2,376
#962058, 6.500%, due 3/1/38		967		1,130
#934006, 6.500%, due 9/1/38		244		296
#986856, 6.500%, due 9/1/38		101		123
#991911, 7.000%, due 11/1/38		103		117
#AL3775, 5.000%, due 1/1/39		1,255		1,378
#AD0752, 7.000%, due 1/1/39		432		522
#AA7611, 5.000%, due 5/1/39		499		549
#AA8443, 5.000%, due 6/1/39		139		154
#AC1619, 5.500%, due 8/1/39		300		332
#AD0315, 6.500%, due 8/1/39		1,503		1,775
#AC9569, 5.000%, due 2/1/40		1,165		1,287
#AD0761, 5.000%, due 2/1/40		174		192
#AD1594, 5.000%, due 2/1/40		176		195

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 87

Bond Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
U.S. Government and U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#932751, 5.000%, due 4/1/40		$	2,477	$	2,735
#AD7137, 5.500%, due 7/1/40			3,239		3,662
#BM1689, 5.500%, due 8/1/40			2,619		2,911
#AH5585, 5.000%, due 2/1/41			123		136
#AI1201, 5.500%, due 4/1/41			3,849		4,350
#AL5815, 5.500%, due 4/1/41			3,177		3,589
#BM3525, 6.000%, due 4/1/41			11,178		12,766
#AI6071, 5.000%, due 6/1/41			1,119		1,236
#AI4222, 5.000%, due 7/1/41			88		96
#AL0672, 5.000%, due 7/1/41			1,982		2,189
#AL0913, 6.000%, due 7/1/41			1,167		1,324
#AL9226, 5.500%, due 12/1/41			13,305		14,939
#AL9225, 6.000%, due 1/1/42			5,908		6,776
#BM1328, 6.000%, due 1/1/42			2,945		3,383
#AK2733, 5.000%, due 2/1/42			1,339		1,477
Total FNMA Mortgage Obligations					131,901
Asset-Backed Securities—1.6%
Tesla Auto Lease Trust—144A, 2018-A, Tranche D, 3.300%, 5/20/20	Baa1		1,325		1,329
Centre Point Funding LLC—144A, 2012-2A, Tranche 1, 2.610%, 8/20/21	Baa1		967		962
Oxford Finance Funding LLC—144A, 2019-1A, Tranche B, 5.438%, 2/15/27	BB		1,180		1,209
SLM Private Education Loan Trust—144A, 2011-A, Tranche A3, 1M USD LIBOR + 2.500%, 4.894%, 1/15/43, VRN	AAA		3,071		3,089
Total Asset-Backed Securities					6,589
Corporate Obligations—44.1%
UBS Group Funding Switzerland AG, 5 year USD ICE Swap + 5.497%, 6.875%, due 3/22/21, VRN	BBB-		2,000		2,085
Fresenius Medical Care US Finance II, Inc.—144A, 5.875%, due 1/31/22	BBB		2,460		2,628
Masco Corporation, 5.950%, due 3/15/22	BBB		4,050		4,383
Discover Financial Services, 5.200%, due 4/27/22	BBB+		3,000		3,213
Jones Lang LaSalle, Inc., 4.400%, due 11/15/22	BBB+		3,900		4,058
Toll Brothers Finance Corporation, 4.375%, due 4/15/23	BBB-		4,250		4,415
Itau Unibanco Holding S.A.—144A, 5.125%, due 5/13/23	Ba3		2,500		2,630
Wells Fargo & Co., 4.480%, due 1/16/24	A		4,250		4,559
Lennar Corporation, 4.500%, due 4/30/24	BBB-		2,450		2,582
Banco Inbursa S.A. Institucion de Banca Multiple-144A, 4.125%, due 6/6/24	BBB+		2,500		2,531

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
Corporate Obligations—(continued)
Grupo Bimbo S.A.B. de C.V.—144A, 3.875%, due 6/27/24	BBB	$	2,600	$	2,689
Iron Mountain, Inc., 5.750%, due 8/15/24	B		675		684
SBA Communications Corporation, 4.875%, due 9/1/24	BB-		2,500		2,584
HSBC Holdings plc, 5 year USD ICE Swap + 3.705%, 6.375%, due 9/17/24, VRN	BBB		4,250		4,402
JPMorgan Chase & Co., 3M USD LIBOR + 3.330%, 6.100%, due 10/1/24, VRN	Baa2		4,265		4,598
Cemex S.A.B. de C.V.—144A, 5.700%, due 1/11/25	BB		3,000		3,124
Centene Corporation, 4.750%, due 1/15/25	BB+		2,000		2,069
Booz Allen Hamilton, Inc.—144A, 5.125%, due 5/1/25	B+		2,500		2,550
DaVita, Inc., 5.000%, due 5/1/25	Ba3		2,500		2,478
Simon Property Group L.P., 3.300%, due 1/15/26	A		4,500		4,650
Penske Automotive Group, Inc., 5.500%, due 5/15/26	Ba3		2,200		2,302
Post Holdings, Inc.—144A, 5.000%, due 8/15/26	B+		2,500		2,544
Xylem, Inc., 3.250%, due 11/1/26	BBB		2,225		2,242
Netflix, Inc., 4.375%, due 11/15/26	BB-		2,000		2,051
Glencore Funding LLC—144A, 4.000%, due 3/27/27	BBB+		4,000		4,043
Hess Corporation, 4.300%, due 4/1/27	BBB-		4,500		4,672
The Chemours Co., 5.375%, due 5/15/27	BB-		2,500		2,394
Sirius XM Radio, Inc.—144A, 5.000%, due 8/1/27	BB		2,500		2,553
Lear Corporation, 3.800%, due 9/15/27	Baa2		3,000		2,972
Motorola Solutions, Inc., 4.600%, due 2/23/28	BBB-		4,250		4,463
The Kroger Co., 8.000%, due 9/15/29	Baa1		3,500		4,670
United Rentals North America, Inc., 5.250%, due 1/15/30	BB-		2,500		2,575
Owens Corning, 7.000%, due 12/1/36	BBB		3,800		4,515
Yum! Brands, Inc., 6.875%, due 11/15/37	B+		2,500		2,644
ConocoPhillips, 6.500%, due 2/1/39	A		3,250		4,570
Citigroup, Inc., 5.875%, due 1/30/42	A		3,500		4,628
Bank of America Corporation, 5.875%, due 2/7/42	A+		3,500		4,658
Cox Communications, Inc.—144A, 4.700%, due 12/15/42	BBB+		4,300		4,288
Mexichem S.A.B. de C.V.—144A, 5.875%, due 9/17/44	BBB		3,000		3,142

See accompanying Notes to Financial Statements.

88 Semiannual Report June 30, 2019

Bond Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
Corporate Obligations—(continued)
AbbVie, Inc., 4.700%, due 5/14/45	A-	$	4,500	$	4,589
ERP Operating L.P., 4.500%, due 6/1/45	A		4,000		4,579
Apple, Inc., 4.650%, due 2/23/46	AA+		3,500		4,157
PepsiCo, Inc., 4.450%, due 4/14/46	A+		3,500		4,193
Verizon Communications, Inc., 4.125%, due 8/15/46	A-		4,000		4,182
Brookfield Finance, Inc., 4.700%, due 9/20/47§	A-		4,500		4,711
CVS Health Corporation, 5.050%, due 3/25/48	BBB		4,250		4,534
Microsoft Corporation, 4.750%, due 11/3/55	AAA		3,500		4,449
AT&T, Inc., 5.700%, due 3/1/57	A-		3,750		4,421
Comcast Corporation, 4.950%, due 10/15/58	A-		2,000		2,445
Altria Group, Inc., 6.200%, due 2/14/59	A3		4,000		4,565
Corning, Inc., 5.850%, due 11/15/68	BBB+		4,000		4,695
Petrobras Global Finance BV, 6.850%, due 6/5/15	Ba2		3,000		3,117
Total Corporate Obligations					183,475
Total Long-Term Investments—97.5% (cost $391,771)					405,286
Repurchase Agreements
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $1,083, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26			1,083		1,083
Total Repurchase Agreement—0.2% (cost $1,083)					1,083

Issuer	Principal Amount			Value
Commercial Paper
Cargill Global Funding plc, 2.353%, due 7/1/19	$	3,500		$	3,500
The Western Union Co., 2.586%, due 7/1/19		3,500			3,500
Total Commercial Paper—1.7% (cost $7,000)					7,000
Total Investments—99.4% (cost $399,854)					413,369
Securities Sold, Not Yet Purchased
U.S. Government Agency—(2.4)%
Federal National Mortgage Association (FNMA)—(2.4)%
TBA, 3.000%, due 7/15/49		(10,000	)		(10,086	)
Total Securities Sold, Not Yet Purchased—(2.4)% (proceeds $10,043)					(10,086	)
Cash and other assets, less liabilities—3.0%					12,489
Net assets—100.0%				$	415,772

The obligations of certain U.S. Government-sponsored securities are neither issued nor guaranteed by the U.S. Treasury.

144A = Security exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be resold in transactions exempt from registration, normally to qualified institutional buyers.

NRSRO = Nationally Recognized Statistical Rating Organization—The credit quality ratings of the securities in the Fund reflect the highest category rating by any of Fitch Ratings, Moody’s Investors Service Inc., or Standard & Poor’s, a division of the McGraw-Hill Companies, Inc.

TBA = To Be Announced-TBAs are mortgage-backed securities traded under delayed delivery commitments, settling after June 30, 2019. The term TBA comes from the fact that the specific mortgage-backed security that will be delivered to fulfill a TBA trade is not designated at the time the trade is made.

VRN = Variable Rate Note

§ = Deemed illiquid pursuant to a Liquidity Risk Management Program approved by the Board of Trustees. This holding represents 1.13% of the Fund’s net assets at June 30, 2019.

(a) Security, or a portion of security, is segregated as collateral for the centrally cleared credit default swap, aggregating a total of $200.

Centrally Cleared Credit Default Swap

Reference Entity	Buy/Sell Protection	Fixed Deal Pay Rate	Payment Frequency	Maturity Date	Cleared Exchange	Notional Amount (in thousands)	Upfront Payment Paid (Received)	Value	Unrealized Appreciation (Depreciation)
CDX.IG-31	Buy	1.000%	3M	December 2023	ICE	$25,000	$ (423)	(573)	$(150)

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 89

	Income Fund
	The Income Fund seeks a high level of current income with relative stability of principal.
	AN OVERVIEW FROM THE PORTFOLIO MANAGER
Christopher T. Vincent	The William Blair Income Fund (Class N shares) returned 4.33%, net of fees, for the six month period ended June 30, 2019. By comparison, the Fund’s benchmark, the Bloomberg Barclays Intermediate Government/Credit Bond Index (the “Index”), returned 4.97%. A couple of factors detracted from the Fund’s performance relative to the Index year-to-date. Interest rate positioning detracted from results, as the Fund had a defensive duration posture during a period of declining interest rates. In addition, the Fund was underweight to BBB-rated corporate bonds, and that hindered relative results as BBB-rated corporate bonds generated strong performance during the period. There were a couple of factors that contributed to the Fund’s relative performance year-to-date. An allocation to higher-coupon segments of the agency mortgage-backed securities market impacted results favorably. Some corporate bond holdings were additive to performance, including positions in bonds issued by Vale Overseas, Ltd., Apple, Inc., and Citigroup, Inc. Please refer to the Fixed Income Market Review and Outlook relating to the Fund beginning on page 83 for additional information.

90 Semiannual Report June 30, 2019

Income Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		4.33	%		4.60	%		1.45	%		1.63	%		3.07	%		—
Class I		4.57			4.93			1.70			1.90			3.31			—
Class R6		—			—			—			—			—			1.47	%
Bloomberg Barclays Intermediate Government/ Credit Bond Index		4.97			6.93			1.99			2.39			3.24			2.45

(a) Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Bloomberg Barclays Intermediate Government/Credit Bond Index indicates broad intermediate government/corporate bond market performance.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all investments in the Fund performed the same, nor is there any guarantee that these investments will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

June 30, 2019 William Blair Funds 91

Income Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Principal
Issuer	Amount		Value
U.S. Government and U.S. Government Agency—55.0%
U.S. Treasury Inflation Indexed Notes/Bonds—2.4%
U.S. Treasury Inflation Indexed Bond, 3.875%, due 4/15/29	$	1,166	$	1,561
Federal Home Loan Mortgage Corp. (FHLMC)—14.0%
#J05444, 6.000%, due 8/1/22		19		19
#E02388, 6.000%, due 9/1/22		27		28
#E02490, 6.000%, due 4/1/23		33		34
#J13022, 4.000%, due 9/1/25		295		310
#G14150, 4.500%, due 4/1/26		81		86
#J16051, 4.500%, due 7/1/26		568		604
#A17603, 5.500%, due 1/1/34		416		465
#G01705, 5.500%, due 6/1/34		819		899
#A45790, 7.500%, due 5/1/35		85		96
#G04126, 6.000%, due 6/1/37		197		227
#G03201, 6.500%, due 6/1/37		117		138
#A66843, 6.500%, due 10/1/37		192		230
#G03534, 6.500%, due 10/1/37		1,460		1,719
#G04564, 6.000%, due 12/1/37		159		182
#A81799, 6.500%, due 9/1/38		173		192
#G05566, 5.500%, due 12/1/38		108		121
#G60366, 6.000%, due 10/1/39		851		972
#G05875, 5.500%, due 2/1/40		81		91
#G61450, 6.000%, due 4/1/40		1,102		1,268
#C03665, 9.000%, due 4/1/41		174		204
#G06583, 5.000%, due 6/1/41		965		1,066
Total FHLMC Mortgage Obligations				8,951
Federal National Mortgage Association (FNMA)—38.6%
#880991, 5.500%, due 1/1/22		33		33
#735574, 8.000%, due 3/1/22		23		24
FNR G93-19 SH, 1M LIBOR + 56.169%, 11.234%, due 4/25/23, VRN		11		12
#982885, 5.000%, due 5/1/23		164		171
#AL0955, 6.000%, due 5/1/23		76		77
#933985, 5.500%, due 8/1/23		86		89
#AL7213, 5.500%, due 12/1/23		454		469
#AL8529, 6.000%, due 11/1/24		1,800		1,877
#255956, 5.500%, due 10/1/25		26		28
#AH0971, 4.000%, due 12/1/25		296		312
#AL2853, 4.500%, due 6/1/26		487		518
#AJ6954, 4.000%, due 11/1/26		128		135
#AL9730, 4.500%, due 2/1/27		955		1,016
#256639, 5.000%, due 2/1/27		5		6
#806458, 8.000%, due 6/1/28		72		80
#AL9857, 4.000%, due 2/1/29		5,646		5,937
#880155, 8.500%, due 7/1/29		142		161
#797846, 7.000%, due 3/1/32		35		35
#745519, 8.500%, due 5/1/32		49		56
#654674, 6.500%, due 9/1/32		34		38
#254693, 5.500%, due 4/1/33		5		5
#555531, 5.500%, due 6/1/33		46		51
#711736, 5.500%, due 6/1/33		70		77
#555591, 5.500%, due 7/1/33		8		8
#CA2754, 4.500%, due 11/1/33		470		505
#AL3455, 5.500%, due 11/1/33		1,313		1,467
#776964, 5.000%, due 4/1/34		219		240

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#725424, 5.500%, due 4/1/34		$	49	$	55
#888884, 5.500%, due 12/1/35			109		121
#888703, 6.500%, due 8/1/37			608		730
#928658, 6.500%, due 9/1/37			19		22
#AL6411, 7.000%, due 12/1/37			554		635
#962058, 6.500%, due 3/1/38			313		365
#991911, 7.000%, due 11/1/38			66		75
#AC9569, 5.000%, due 2/1/40			155		171
#BM1689, 5.500%, due 8/1/40			354		393
#AL5815, 5.500%, due 4/1/41			454		513
#BM3525, 6.000%, due 4/1/41			992		1,133
#AL9226, 5.500%, due 12/1/41			4,205		4,721
#BM1328, 6.000%, due 1/1/42			449		516
#AL9225, 6.000%, due 1/1/42			1,625		1,863
Total FNMA Mortgage Obligations					24,740
Asset-Backed Securities—4.4%
Tesla Auto Lease Trust-144A, 2018-A, Tranche C, 2.970%, 4/20/20	Aa3		150		150
Capital One Multi-Asset Execution Trust, 2015-A3, Tranche A3, 1M LIBOR + 0.400%, 2.794%, 3/15/23, VRN	AAA		750		752
Chase Issuance Trust, 2018-A1, Tranche A1, 1M LIBOR + 0.200%, 2.594%, 4/17/23, VRN	AAA		500		500
Verizon Owner Trust, 2018-A, Tranche A1B, 1M LIBOR + 0.240%, 2.623%, 4/20/23, VRN	AAA		598		598
Oxford Finance Funding LLC—144A, 2019-1A, Tranche A2, 4.459%, 2/15/27	BB		500		514
SLM Private Education Loan Trust-144A, 2011-A, Tranche A3,
1M USD LIBOR + 2.500%, 4.894%, 1/15/43, VRN	AAA		307		309
Total Asset-Backed Securities					2,823
Corporate Obligations—35.4%
Burlington Northern Santa Fe LLC, 4.700%, due 10/1/19	A+		650		653
JPMorgan Chase & Co., 3M USD LIBOR + 3.320%, 5.639%, due 10/1/19, VRN	Baa2		500		499
Citigroup, Inc., 2.450%, due 1/10/20	A		650		650
Branch Banking & Trust Co., 3M USD LIBOR + 0.450%, 3.047%, due 1/15/20, VRN	A1		500		501
American Express Credit Corporation, 3M USD LIBOR + 0.730%, 3.251%, due 5/26/20, VRN	A2		500		503

See accompanying Notes to Financial Statements.

92 Semiannual Report June 30, 2019

Income Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
U.S. Government Agency—(continued)
Corporate Obligations—(continued)
Georgia-Pacific LLC—144A, 5.400%, due 11/1/20	A+	$	600	$	624
HSBC Holdings plc, 3M USD LIBOR + 2.240%, 4.693%, due 3/8/21, VRN	AA-		500		514
Westpac Banking Corporation, 3M USD LIBOR + 1.000%, 3.535%, due 5/13/21, VRN	AA-		500		507
Chevron Corporation, 3M USD LIBOR + 0.950%, 3.475%, due 5/16/21, VRN	AA		500		508
The Charles Schwab Corporation, 3M USD LIBOR + 0.320%, 2.842%, due 5/21/21, VRN	A		500		501
Capital One Financial Corporation, 4.750%, due 7/15/21	A-		650		680
Apple, Inc., 1.550%, due 8/4/21	AA+		650		644
Lloyds Banking Group plc, 3.000%, due 1/11/22	A+		650		657
FedEx Corporation, 3.400%, due 1/14/22	BBB		500		513
Bancolombia S.A., 5.125%, due 9/11/22	BBB-		400		419
Jones Lang LaSalle, Inc., 4.400%, due 11/15/22	BBB+		500		520
Toll Brothers Finance Corporation, 4.375%, due 4/15/23	BBB-		500		519
Ryder System, Inc., 3.750%, due 6/9/23	A-		650		677
Wells Fargo & Co., 4.480%, due 1/16/24	A		650		697
The Goldman Sachs Group, Inc., 4.000%, due 3/3/24	A		650		690
Bank of America Corporation, 3M USD LIBOR + 0.780%, 3.550%, due 3/5/24, VRN	A+		650		674
Mitsubishi UFJ Financial Group, Inc., 3.407%, due 3/7/24	A1		650		675
Grupo Bimbo S.A.B. de C.V—144A, 3.875%, due 6/27/24	BBB		500		517
BNP Paribas S.A., 4.250%, due 10/15/24	A		650		684
CVS Health Corporation, 4.100%, due 3/25/25	BBB		500		528
AbbVie, Inc., 3.600%, due 5/14/25	A-		650		672
ERP Operating L.P., 3.375%, due 6/1/25	A		650		680
Comcast Corporation, 3.950%, due 10/15/25	A-		650		702
Intercontinental Exchange, Inc., 3.750%, due 12/1/25	A		650		695
Simon Property Group L.P., 3.300%, due 1/15/26	A		650		672
AT&T, Inc., 4.125%, due 2/17/26	A-		650		692

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
U.S. Government Agency—(continued)
Corporate Obligations—(continued)
ConocoPhillips Co., 4.950%, due 3/15/26	A	$	650	$	743
Brookfield Finance, Inc., 4.250%, due 6/2/26	A-		650		679
Amazon.com, Inc., 3.150%, due 8/22/27	AA-		650		684
Motorola Solutions, Inc., 4.600%, due 2/23/28	BBB-		500		525
Quest Diagnostics, Inc., 4.200%, due 6/30/29	BBB+		675		722
The Kroger Co., 8.000%, due 9/15/29	Baa1		500		667
Total Corporate Obligations					22,687
Total Long-Term Investments—94.8% (cost $60,420)					60,762
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $1,878, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26			1,878		1,878
Total Repurchase Agreement—2.9% (cost $1,878)					1,878
Commercial Paper
Cargill Global Funding plc, 2.353%, due 7/1/19			600		600
Eli Lilly & Co., 2.383%, due 7/2/19			600		600
Total Commercial Paper—1.9% (cost $1,200)					1,200
Total Investments—99.6% (cost $63,498)					63,840

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 93

Income Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

	Principal
Issuer	Amount			Value
Securities Sold, Not Yet Purchased
U.S. Government Agency—(4.7)%
Federal National Mortgage Association (FNMA)—(4.7)% TBA, 2.500%, due 7/1/34	$	(3,000	)	$	(3,021	)
Total Securities Sold, Not Yet Purchased—(4.7)%(proceeds $3,003)					(3,021	)
Cash and other assets,less liabilities—5.1%					3,252
Net assets—100.0%				$	64,071

The obligations of certain U.S. Government-sponsored securities are neither issued nor guaranteed by the U.S. Treasury.

144A = Security exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be resold in transactions exempt from registration, normally to qualified institutional buyers.

NRSRO = Nationally Recognized Statistical Rating Organization—The credit quality ratings of the securities in the Fund reflect the highest category rating by any of Fitch Ratings, Moody’s Investors Service Inc., or Standard & Poor’s, a division of the McGraw-Hill Companies, Inc.

TBA = To Be Announced—TBAs are mortgage-backed securities traded under delayed delivery commitments, settling after June 30, 2019. The term TBA comes from the fact that the specific mortgage-backed security that will be delivered to fulfill a TBA trade is not designated at the time the trade is made.

VRN = Variable Rate Note

See accompanying Notes to Financial Statements.

94 Semiannual Report June 30, 2019

	Low Duration Fund
	The Low Duration Fund seeks to maximize total return. Total return includes both income and capital appreciation.
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Paul J. Sularz   Christopher T. Vincent	The William Blair Low Duration Fund (Class N shares) returned 2.46%, net of fees, for the six month period ended June 30, 2019. By comparison, the Fund’s benchmark, the Bank of America/Merrill Lynch 1-Year U.S. Treasury Note Index (the “Index”), returned 1.76%. A couple of factors contributed to the Fund’s performance relative to the Index year-to-date. The Fund’s holdings of higher-coupon agency mortgage-backed securities was additive to results. An allocation to floating-rate corporate and asset-backed securities positively contributed to performance due to the additional income the securities offered. The Fund’s interest rate positioning also impacted results favorably, as the Fund had more duration during a period of declining short-term interest rates. A couple of factors detracted from the Fund’s performance relative to the Index year-to-date. Residual cash held in the portfolio detracted from performance as short-term bonds outperformed cash during the period. The Fund also hedged some of its interest rate risk, and these hedges detracted from results as interest rates declined. Please refer to the Fixed Income Market Review and Outlook relating to the Fund beginning on page 83 for additional information.

June 30, 2019 William Blair Funds 95

Low Duration Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			Since Inception(a)
Class N		2.46	%		2.97	%		1.38	%		1.14	%		1.21	%
Class I		2.54			3.26			1.57			1.33			1.38
Class R6		2.56			3.29			1.61			1.38			1.48
Bank of America Merrill Lynch 1-Year U.S. Treasury Note Index		1.76			2.98			1.43			1.02			0.73

(a) Since inception is for the period from December 1, 2009 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Bank of America Merrill Lynch 1-Year U.S. Treasury Note Index is comprised of a single U.S. Treasury Note issue purchased at the beginning of the month and held for a full month. Each month the index is rebalanced and the issue selected is the outstanding U.S. Treasury Note that matures closest to, but not beyond one year from the rebalancing date.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all investments in the Fund performed the same, nor is there any guarantee that these investments will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

96 Semiannual Report June 30, 2019

Low Duration Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (Unaudited)

Issuer	Principal Amount		Value
U.S. Government Agency—53.0%
Federal Home Loan Mortgage Corp. (FHLMC)—13.8%
#B17294, 5.000%, due 11/1/19	$	6	$	6
#B19222, 4.500%, due 4/1/20		9		9
#J02537, 5.000%, due 9/1/20		5		6
#G11836, 5.500%, due 12/1/20		2		2
#E02322, 5.500%, due 5/1/22		11		11
#G12725, 6.000%, due 6/1/22		49		50
#G13124, 6.000%, due 12/1/22		123		127
#J06871, 5.500%, due 1/1/23		26		27
#J08450, 5.500%, due 7/1/23		17		18
#J08703, 5.500%, due 9/1/23		20		20
#C00351, 8.000%, due 7/1/24		26		28
#J11208, 5.000%, due 11/1/24		39		40
#G00363, 8.000%, due 6/1/25		41		45
#C80329, 8.000%, due 8/1/25		8		9
#G04821, 8.500%, due 7/1/31		1,478		1,802
#G07837, 6.500%, due 2/1/38		1,035		1,228
#G04641, 6.000%, due 6/1/38		1,163		1,326
#A81372, 6.000%, due 8/1/38		196		224
#G04687, 6.000%, due 9/1/38		50		57
#G04745, 6.000%, due 9/1/38		180		205
#A81799, 6.500%, due 9/1/38		162		180
#G06085, 6.500%, due 9/1/38		47		55
#G05723, 6.500%, due 11/1/38		798		944
#G61450, 6.000%, due 4/1/40		5,934		6,827
#4122, Tranche FP, 1M LIBOR + 0.400%, 2.794%, due 10/15/42, VRN		606		605
Total FHLMC Mortgage Obligations				13,851
Federal National Mortgage Association (FNMA)—39.2%
#785259, 5.000%, due 8/1/19		1		1
#761530, 5.500%, due 8/1/19		1		1
#761489, 5.500%, due 9/1/19		1		1
#725953, 5.000%, due 10/1/19		1		1
#357865, 5.000%, due 7/1/20		10		11
#879607, 5.500%, due 4/1/21		8		8
#831497, 6.000%, due 4/1/21		39		39
#831525, 5.500%, due 6/1/21		12		12
#880993, 6.000%, due 1/1/22		3		3
#888982, 6.000%, due 12/1/22		56		58
#972934, 5.500%, due 2/1/23		73		75
#889670, 5.500%, due 6/1/23		15		16
#AE0011, 5.500%, due 9/1/23		16		16
#AL7213, 5.500%, due 12/1/23		724		748
#995395, 6.000%, due 12/1/23		42		44
#AL7638, 5.500%, due 1/1/24		2,130		2,204
#190988, 9.000%, due 6/1/24		11		11
#AL8529, 6.000%, due 11/1/24		6,939		7,235
#AL2853, 4.500%, due 6/1/26		1,469		1,563
#AL9730, 4.500%, due 2/1/27		1,433		1,524
#AL9857, 4.000%, due 2/1/29		2,126		2,236
#555933, 7.000%, due 6/1/32		406		462
#886762, 7.000%, due 9/1/36		223		264
#948637, 6.500%, due 8/1/37		208		241

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#888703, 6.500%, due 8/1/37		$	2,273	$	2,727
#888530, 7.500%, due 8/1/37			1,634		1,990
#AL6411, 7.000%, due 12/1/37			1,731		1,984
#AD0100, 7.000%, due 12/1/38			563		674
#AE0934, 6.500%, due 10/1/39			1,891		2,243
#BM3525, 6.000%, due 4/1/41			3,571		4,078
#AL9226, 5.500%, due 12/1/41			3,138		3,523
#BM1328, 6.000%, due 1/1/42			1,603		1,841
#AL9225, 6.000%, due 1/1/42			2,954		3,388
Total FNMA Mortgage Obligations					39,222
Asset-Backed Securities—12.0%
Tesla Auto Lease Trust-144A, 2018-A, Tranche A, 2.320%, 12/20/19	Aaa		80		80
Nissan Auto Lease Trust, 2018-A, Tranche A2B, 1M USD LIBOR + 0.150%, 2.634%, 2/16/21, VRN	AAA		1,380		1,379
GM Financial Consumer Automobile Receivables Trust, 2018-3, Tranche A2B, 1M USD LIBOR + 0.110%, 2.504%, 7/16/21, VRN	AAA		1,267		1,267
Ford Credit Auto Owner Trust, 2018-B, Tranche A2B, 1M USD LIBOR + 0.120%, 2.514%, 9/15/21, VRN	Aaa		536		536
PFS Financing Corporation-144A, 2018-A, Tranche A, 1M USD LIBOR + 0.400%, 2.794%, 2/15/22, VRN	AAA		1,500		1,500
Verizon Owner Trust-144A, 2017-3A, Tranche A1B, 1M LIBOR + 0.270%, 2.653%, 4/20/22, VRN	AAA		1,500		1,502
Mercedes-Benz Master Owner Trust-144A, 2017-BA, Tranche A, 1M LIBOR + 0.420%, 2.814%, 5/16/22, VRN	Aaa		2,280		2,284
GMF Floorplan Owner Revolving Trust-144A, 2017-2, Tranche A2, 1M USD LIBOR + 0.430%, 2.824%, 7/15/22, VRN	Aaa		1,000		1,002
Oxford Finance Funding LLC-144A, 2019-1A, Tranche A2, 4.459%, 2/15/27	BB		1,000		1,028
SLM Private Education Loan Trust-144A, 2011-A, Tranche A3, 1M USD LIBOR + 2.500%, 4.894%, 1/15/43, VRN	AAA		1,443		1,452
Total Asset-Backed Securities					12,030

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 97

Low Duration Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (Unaudited)

Issuer	NRSRO Rating (unaudited)	Principal Amount		Value
Corporate Obligations—33.3%
Mondelez International Holdings Netherlands BV-144A, 3M USD LIBOR + 0.610%, 3.192%, due 10/28/19, VRN	A3	$	1,750	$	1,752
Daimler Finance North America LLC-144A, 3M USD LIBOR + 0.620%, 3.203%, due 10/30/19, VRN	A		1,600		1,603
Citigroup, Inc., 3M USD LIBOR + 0.790%, 3.374%, due 1/10/20, VRN	A		1,853		1,859
Branch Banking & Trust Co., 3M USD LIBOR + 0.450%, 3.047%, due 1/15/20, VRN	A1		1,700		1,703
Capital One Financial Corporation, 3M USD LIBOR + 0.760%, 3.295%, due 5/12/20, VRN	A-		1,750		1,758
Diageo Capital plc, 3M USD LIBOR + 0.240%, 2.760%, due 5/18/20, VRN	A-		750		751
Harley-Davidson Financial Services, Inc.-144A, 3M USD LIBOR + 0.500%, 3.022%, due 5/21/20, VRN	A		1,000		1,000
National Australia Bank Ltd.-144A, 3M USD LIBOR + 0.510%, 3.033%, due 5/22/20, VRN	AA-		1,750		1,758
John Deere Capital Corporation, 3M USD LIBOR + 0.290%, 2.633%, due 6/22/20, VRN	A		1,000		1,002
Nissan Motor Acceptance Corp.-144A, 3M USD LIBOR + 0.390%, 2.987%, due 7/13/20, VRN	A-		1,250		1,250
Caterpillar Financial Services Corporation, 3M USD LIBOR + 0.290%, 2.793%, due 9/4/20, VRN	A		1,000		1,002
Apple, Inc., 3M USD LIBOR + 1.130%, 3.654%, due 2/23/21, VRN	AA+		1,000		1,017
JPMorgan Chase & Co., 3M USD LIBOR + 1.480%, 4.000%, due 3/1/21, VRN	AA-		1,750		1,781
Wells Fargo & Co., 3M USD LIBOR + 1.340%, 3.843%, due 3/4/21, VRN	A+		1,750		1,777
HSBC Holdings plc, 3M USD LIBOR + 2.240%, 4.693%, due 3/8/21, VRN	AA-		1,750		1,801

Issuer	NRSRO Rating (unaudited)	Principal Amount			Value
Corporate Obligations—(continued)
Bank of America Corporation, 3M USD LIBOR + 1.420%, 4.012%, due 4/19/21, VRN	A+	$	1,000	$	1,019
The Goldman Sachs Group, Inc., 3M USD LIBOR + 1.360%, 3.940%, due 4/23/21, VRN	A		1,000		1,015
Westpac Banking Corporation, 3M USD LIBOR + 1.000%, 3.535%, due 5/13/21, VRN	AA-		1,750		1,774
The Charles Schwab Corporation, 3M USD LIBOR + 0.320%, 2.842%, due 5/21/21, VRN	A		1,000		1,002
The Toronto-Dominion Bank, 3M USD LIBOR + 0.430%, 2.881%, due 6/11/21, VRN	Aa1		1,000		1,004
Barclays plc, 3M USD LIBOR + 2.110%, 4.655%, due 8/10/21, VRN	A		1,750		1,789
KeyBank NA, 3M USD LIBOR + 0.810%, 3.333%, due 11/22/21, VRN	A-		1,750		1,766
Bristol-Myers Squibb Co.-144A, 2.600%, due 5/16/22	A+		1,000		1,013
Ryder System, Inc., 2.875%, due 6/1/22	A-		1,150		1,164
Total Corporate Obligations					33,360
Total Long-Term Investments—98.3% (cost $98,667)					98,463
Repurchase Agreement
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $731, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26			731		731
Total Repurchase Agreement—0.7% (cost $731)					731
Commercial Paper
Cargill Global Funding plc, 2.353%, due 7/1/19			1,500		1,500
Total Commercial Paper—1.5% (cost $1,500)					1,500
Total Investments—100.5% (cost $100,898)					100,694

See accompanying Notes to Financial Statements.

98 Semiannual Report June 30, 2019

Low Duration Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (Unaudited)

Issuer	Principal Amount			Value
Securities Sold, Not Yet Purchased
U.S. Government Agency
Federal National Mortgage Association (FNMA)—(12.1)%
TBA, 2.500%, due 7/1/34	$	(12,000	)	$	(12,085	)
Total Securities Sold, Not Yet Purchased—(12.1)% (proceeds $12,013)					(12,085	)
Cash and other assets, less liabilities—11.6%					11,584
Net assets—100.0%				$	100,193

The obligations of certain U.S. Government-sponsored securities are neither issued nor guaranteed by the U.S. Treasury.

144A = Security exempt from registration under Rule 144A of the Securities Act of 1933. These securities may be resold in transactions exempt from registration, normally to qualified institutional buyers.

NRSRO = Nationally Recognized Statistical Rating Organization—The credit quality ratings of the securities in the Fund reflect the highest category rating by any of Fitch Ratings, Moody’s Investors Service Inc., or Standard & Poor’s, a division of the McGraw-Hill Companies, Inc.

TBA = To Be Announced—TBAs are mortgage-backed securities traded under delayed delivery commitments, settling after June 30, 2019. The term TBA comes from the fact that the specific mortgage-backed security that will be delivered to fulfill a TBA trade is not designated at the time the trade is made.

VRN = Variable Rate Note

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 99

	Macro Allocation Fund
	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Thomas Clarke Brian D. Singer	The William Blair Macro Allocation Fund (Class N shares) posted a 2.45% increase, net of fees, for the six-month period ending June 30, 2019. By comparison, the Fund’s benchmark index, the Bank of America/Merrill Lynch 3-Month U.S. Treasury Bill Index (the “Index”), increased 1.24%. After a turbulent end to calendar year 2018, equity markets rebounded handsomely over the past six months, with the MSCI All Country World Index gaining +16.38% in fully hedged terms. Strong performance came from European, U.S., and Australian equity markets while Japanese and emerging markets lagged (though still positive). Bond yields fell, generally speaking, providing strong positive returns to bond indices. Within currencies, strong performance can be seen in energy-sensitive currencies such as the Russian ruble and Mexican peso, while underperformers have been developed European currencies such as the Swedish krona, euro, and British pound. The Fund’s market and currency strategies were both positive during the period. Within markets, the Fund saw positive contributions from long exposure to Europe, the U.K., Singapore, and emerging market equities. Detracting from the Fund’s market strategy performance was short exposure to Canadian and Swiss equities, short exposure to European sovereign bonds, and sector positioning within U.S. equities. Within the Fund’s active currency strategy, positive performance was gained from long exposure to the Philippine peso, Mexican peso, and Russian ruble. Negative contribution to performance came from the Fund’s short exposure to the Thai baht, Indonesian rupiah, and long exposure to the Swedish krona. We have observed for some time that a large part of the influence on equities, when they have been rallying, has been central bank policy. This includes direct communication from monetary authorities about what they might do, as well as changes in market expectations ahead of such communication when investors collectively predict what central bank committees might do. More specifically, the perception that the Federal Reserve (the “Fed”) and the European Central Bank (the “ECB”) will continue to act to contain equity declines and fuel price recoveries has become pervasive. Linking the developments in equities and bonds in the last six months reveals as much, and repeats a pattern very similar to what happened in the fourth quarter of 2018 and earlier this year. As stocks fall—as they did in May [of 2019] and also October through December of 2018—interest rate markets sharply revise downward monetary expectations, changing them from expected rate increases, to no changes, to cuts, and to longer periods at low or negative levels. In both recent episodes, this adjustment has mostly happened before central bank spokespeople have commented. Subsequently, more dovish (than before) statements from Fed Chairman Powell and ECB President Draghi confirm these changed expectations—anchoring them at lower levels, after which equities rebounded. We have opined that such apparent “ceding of control” of policy to market sentiment is not a good thing, even though it has ostensibly been effective if its aim was indeed to underwrite stock markets. What appears to have developed is that the “cycle” outlined previously has recurred with increasing frequency; the May 2019 market downturn produced a response from central banks (ratifying more dovish monetary assessments) after less time and after a smaller price decline than the downturn seen at the end of 2018. In this sense, it is less of an issue in our eyes that central banks can support markets, than that they are having to do so at more frequent intervals. While we find some equity markets fundamentally attractive (several in Europe and developed Asia-Pacific, also Brazil, India, Vietnam), we remain reluctant to assume significant aggregate long equity exposure in portfolios because, overall, our analysis leads us to expect relatively meager equity returns and largely unpredictable negative shocks to the downside that seem to increasingly lead to additional ratchets in expectations toward ever

100 Semiannual Report June 30, 2019

Macro Allocation Fund

AN OVERVIEW FROM THE PORTFOLIO MANAGERS (CONTINUED)

greater monetary accommodation, and which likely require major central banks to confirm the same. Furthermore, global economic activity is slowing and has been doing so for more than a year, which is reflected in Industrial Purchasing Managers’ Index (“PMI”) reports across the world. Such indicators are consistent with almost flat growth (i.e. no expansion) on an aggregate basis. While this data provides justification for easier monetary expectations (justification other than just market price weakness), it leads us to believe that the forward-looking environment for equities is not as strong right now.

In the current environment, we have continued our stance of carrying low total equity exposure (systematic “beta”), and employing linear option replication, which involves selling equities as they depreciate and buying as they appreciate, as a means of navigating what we’ve discussed previously. Contrastingly, we have looked to increase risk exposure to areas of our investment universe where we believe that opportunities are not exposed to systematic risk, and this has mostly involved our currency strategy. Generally, we remain long emerging market currencies and short developed market currencies, but recent strategy changes have not been in this direction. Also, we continue to see a lack of correlation between movements in exchange rates and equity markets so far in 2019. It is especially notable that we have not seen emerging currencies depreciate along with equity markets so far, providing the breadth and diversification that we seek when investing in currencies.

June 30, 2019 William Blair Funds 101

Macro Allocation Fund

Performance Highlights (Unaudited)

Average Annual Total Return through 6/30/2019
	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		2.45	%		2.77	%		2.63	%		0.43	%		4.35	%
Class I(a)		2.64			3.09			2.93			0.72			4.64
BofA Merrill Lynch 3-Month U.S. Treasury Bill Index(a)		1.24			2.31			1.38			0.87			0.60
Class R6(b)		2.64			3.14			3.01			0.81			1.44
BofA Merrill Lynch 3-Month U.S. Treasury Bill Index(b)		1.24			2.31			1.38			0.87			0.77

(a)	Since inception is for the period from November 29, 2011 (Commencement of Operations) to June 30, 2019.
(b)	Since inception is for the period from October 21, 2013 (Commencement of Operations) to June 30, 2019.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are average annual total returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272, or visit our Web site atwww.williamblairfunds.com. The Fund involves a high level of risk and may not be appropriate for everyone. You could lose money by investing in the Fund. There can be no assurance that the Fund’s investment objective will be achieved or that the Fund’s investment strategies will be successful. The Fund is not a complete investment program. From time to time, the investment adviser may waive fees or reimburse expenses for the Fund. Without these waivers/reimbursements, performance would be lower. Class N shares are not subject to a sales load. Class I shares are not subject to a sales load or distribution (Rule 12b-1) fees. Class R6 shares are not subject to a sales load, distribution (Rule 12b-1) fees, or sub-transfer agent fees.

The performance highlights and graph presented above do not reflect the deduction of taxes that a shareholder would pay on fund distributions or the redemption of fund shares.

The Bank of America (“BofA”) Merrill Lynch 3-Month U.S. Treasury Bill Index measures total return on cash, including price and interest income, based on short-term government Treasury Bills of about 90-day maturity. The Index is unmanaged, does not incur fees or expenses, and cannot be invested in directly.

This report identifies the Fund’s investments on June 30, 2019. These holdings are subject to change. Not all investments in the Fund performed the same, nor is there any guarantee that these investments will perform as well in the future. Market forecasts provided in this report may not necessarily come to pass.

Portfolio Allocation (Unaudited)

The table below provides the allocation of the Fund’s holdings as a percent of net assets as of June 30, 2019.

Category	% of net assets
Equity Exchange-Traded Funds		59.6	%
Fixed Income Exchange-Traded Funds		4.3
Foreign Government Bond		2.3
Repurchase Agreement		7.5
U.S. Government		23.5
Cash and Other Assets, Less Liabilities		2.8
Net Assets		100.0	%

See accompanying Notes to Financial Statements.

102 Semiannual Report June 30, 2019

Macro Allocation Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Issuer	Shares or Principal Amount		Value
Exchange-Traded Funds—63.9%
Equity Exchange-Traded Funds—59.6%
Consumer Staples Select Sector SPDR Fund		231,600	$	13,449
Dragon Capital-Vietnam Enterprise Investments, Ltd. Class “C”§		3,275,100		18,134
Energy Select Sector SPDR Fund		307,900		19,616
Global X MSCI Greece ETF		2,607,200		24,925
iShares Core MSCI Emerging Markets ETF		694,600		35,730
iShares MSCI Brazil ETF		826,300		36,126
iShares MSCI India ETF		274,500		9,690
iShares MSCI Malaysia ETF		297,500		8,845
iShares Russell 1000 Value ETF		283,100		36,016
SPDR S&P 500 ETF Trust		1,095,700		321,040
Utilities Select Sector SPDR Fund		77,800		4,639
VanEck Vectors Russia ETF		98,700		2,332
Total Equity Exchange-Traded Funds				530,542
Fixed Income Exchange-Traded Funds—4.3%
iShares iBoxx $ Investment Grade Corporate Bond ETF		220,300		27,399
SPDR Bloomberg Barclays High Yield Bond ETF		95,000		10,349
Total Fixed Income Exchange-Traded Funds				37,748
Total Exchange-Traded Funds—63.9% (cost $519,931)				568,290
Foreign Government Bond—2.3%
Malaysia
Malaysia Government Bond, 3.492%, due 3/31/20	MYR    85,568			20,759
Total Foreign Government Bonds—2.3% (cost $20,817)				20,759
Repurchase Agreement—7.5%
Fixed Income Clearing Corporation, 0.500% dated 6/28/19, due 7/1/19, repurchase price $66,872, collateralized by U.S. Treasury Note, 1.500%, due 8/15/26		66,869		66,869
Total Repurchase Agreement—7.5% (cost $66,869)				66,869

Issuer	Principal Amount		Value
U.S. Government—23.5%
U.S. Treasury Bill, 2.243%, due 7/18/19		23,000	$	22,978
U.S. Treasury Bill, 2.348%, due 8/15/19(a)		23,000		22,940
U.S. Treasury Bill, 2.446%, due 9/12/19		15,000		14,937
U.S. Treasury Bill, 2.512%, due 10/10/19		15,000		14,912
U.S. Treasury Bill, 2.557%, due 11/7/19		15,000		14,889
U.S. Treasury Bill, 2.543%, due 12/5/19(b)		15,000		14,869
U.S. Treasury Bill, 2.530%, due 1/2/20(a)(b)		15,000		14,844
U.S. Treasury Bill, 2.540%, due 1/30/20(a)(b)		15,000		14,832
U.S. Treasury Bill, 2.499%, due 2/27/20(a)(b)		15,000		14,805
U.S. Treasury Bill, 2.370%, due 3/26/20(a)(b)		15,000		14,782
U.S. Treasury Bill, 2.405%, due 4/23/20(a)(b)		15,000		14,762
U.S. Treasury Bill, 2.350%, due 5/21/20(b)		15,000		14,742
U.S. Treasury Bill, 2.063%, due 6/18/20		15,000		14,724
U.S. Government—(continued)
Total U.S. Government—23.5% (cost $208,624)			$	209,016
Total Investments in Securities—97.2% (cost $816,241)				864,934
Cash and other assets, less liabilities—2.8%				25,343
Net assets—100.0%			$	890,277

§ = Deemed illiquid pursuant to a Liquidity Risk Management Program approved by the Board of Trustees. This holding represents 2.04% of the Fund’s net assets at June 30, 2019.

(a) Security, or portion of security, is segregated as collateral for centrally cleared swaps and to cover initial margin requirements on open futures contracts aggregating a total value of $38,766 (in thousands).

(b) Security, or portion of security, is pledged as collateral for OTC swap contracts aggregating a total value of $5,925 (in thousands).

For securities primarily traded on exchanges or markets that close before the close of regular trading on the New York Stock Exchange, the Fund may use an independent pricing service to fair value price the securities pursuant to Valuation Procedures approved by the Board of Trustees.

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 103

Macro Allocation Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Forward Foreign Currency Contracts

Settlement Date	Deliver/Receive	Counterparty	Local Currency (in thousands)		USD (Base) Purchased or Sold			Current Value			Net Unrealized Appreciation (Depreciation)
Purchased
7/17/19	New Turkish Lira	Citibank N.A. London		423,404		$	72,001		$	72,422		$	421
9/18/19	Australian Dollar	Citibank N.A. London		4,713			3,318			3,317			(1	)
9/18/19	Yuan Renminbi	Citibank N.A. London		7,045			1,025			1,025			—
9/18/19	Colombian Peso	Citibank N.A. London		124,106,120			37,888			38,434			546
9/18/19	Czech Koruna	Citibank N.A. London		57,208			2,562			2,561			(1	)
9/18/19	Euro	Citibank N.A. London		2,235			2,557			2,557			—
9/18/19	Hong Kong Dollar	Citibank N.A. London		12,847			1,646			1,645			(1	)
9/18/19	Indian Rupee	Citibank N.A. London		3,521,344			50,112			50,531			419
9/18/19	Indonesian Rupiah	Citibank N.A. London		45,209,161			3,177			3,168			(9	)
9/18/19	Israeli Shekel	Citibank N.A. London		6,052			1,704			1,704			—
9/18/19	Japanese Yen	Citibank N.A. London		6,136,233			57,004			57,247			243
9/18/19	Mexican Peso	Citibank N.A. London		1,673,178			86,150			86,020			(130	)
9/18/19	New Zealand Dollar	Citibank N.A. London		5,749			3,869			3,868			(1	)
9/18/19	Norwegian Krone	Citibank N.A. London		334,496			38,837			39,298			461
9/18/19	Philippine Peso	Citibank N.A. London		6,302,576			120,623			122,530			1,907
9/18/19	Polish Zloty	Citibank N.A. London		102,574			27,337			27,522			185
9/18/19	Russian Ruble	Citibank N.A. London		1,648,886			25,230			25,790			560
9/18/19	Singapore Dollar	Citibank N.A. London		133,285			97,827			98,630			803
9/18/19	South African Rand	Citibank N.A. London		516,104			34,426			36,278			1,852
9/18/19	South Korean Won	Citibank N.A. London		2,169,310			1,880			1,879			(1	)
9/18/19	Swedish Krona	Citibank N.A. London		715,028			76,294			77,436			1,142
9/18/19	Swiss Franc	Citibank N.A. London		4,625			4,772			4,772			—
9/18/19	Taiwan Dollar	Citibank N.A. London		74,120			2,404			2,402			(2	)
9/18/19	Thai Baht	Citibank N.A. London		309,205			10,104			10,102			(2	)
												$	8,391
Sold
9/18/19	Australian Dollar	Citibank N.A. London		82,676		$	57,583		$	58,182		$	(599	)
9/18/19	Brazilian Real	Citibank N.A. London		46,895			12,124			12,120			4
9/18/19	Yuan Renminbi	Citibank N.A. London		186,430			26,859			27,121			(262	)
9/18/19	Colombian Peso	Citibank N.A. London		7,011,806			2,160			2,171			(11	)
9/18/19	Czech Koruna	Citibank N.A. London		1,000,568			44,328			44,797			(469	)
9/18/19	Euro	Citibank N.A. London		85,166			97,106			97,452			(346	)
9/18/19	Hong Kong Dollar	Citibank N.A. London		250,025			31,947			32,018			(71	)
9/18/19	Hungarian Forint	Citibank N.A. London		4,949,472			17,501			17,507			(6	)
9/18/19	Indian Rupee	Citibank N.A. London		1,337,096			19,036			19,187			(151	)
9/18/19	Indonesian Rupiah	Citibank N.A. London		826,987,275			56,955			57,952			(997	)
9/18/19	Israeli Shekel	Citibank N.A. London		105,493			29,604			29,705			(101	)
9/18/19	Japanese Yen	Citibank N.A. London		278,874			2,601			2,602			(1	)
9/18/19	Mexican Peso	Citibank N.A. London		73,492			3,777			3,778			(1	)
9/18/19	New Zealand Dollar	Citibank N.A. London		126,579			83,506			85,163			(1,657	)
9/18/19	Norwegian Krone	Citibank N.A. London		19,128			2,246			2,247			(1	)
9/18/19	Philippine Peso	Citibank N.A. London		283,727			5,506			5,516			(10	)
9/18/19	Polish Zloty	Citibank N.A. London		5,782			1,551			1,551			—
9/18/19	Russian Ruble	Citibank N.A. London		94,082			1,472			1,471			1
9/18/19	Singapore Dollar	Citibank N.A. London		5,882			4,352			4,353			(1	)
9/18/19	South African Rand	Citibank N.A. London		27,788			1,953			1,953			—
9/18/19	South Korean Won	Citibank N.A. London		50,414,029			42,702			43,658			(956	)
9/18/19	Swedish Krona	Citibank N.A. London		32,942			3,567			3,568			(1	)
9/18/19	Swiss Franc	Citibank N.A. London		101,840			103,355			105,075			(1,720	)
9/18/19	Taiwan Dollar	Citibank N.A. London		1,199,235			38,198			38,867			(669	)
9/18/19	Thai Baht	Citibank N.A. London		4,036,345			129,552			131,864			(2,312	)
												$	(10,337	)
Total net unrealized appreciation (depreciation) on forward foreign currency contracts												$	(1,946	)

See accompanying Notes to Financial Statements.

104 Semiannual Report June 30, 2019

Macro Allocation Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Futures Contracts

Number of Contracts	Description	Expiration Date	Local Currency	Notional Value (Local, in Thousands)		Notional Amount (USD)			Notional Value (USD)			Net Unrealized Appreciation (Depreciation)
Long
469	CAC 40 Index	July 2019	Euro		25,950		$	28,612		$	29,507		$	895
343	IBEX 35 Index	July 2019	Euro		31,463			35,452			35,777			325
78	HSCEI Future	July 2019	Hong Kong Dollar		42,257			5,421			5,409			(12	)
1,296	MSCI Singapore ETS Index	July 2019	Singapore Dollar		49,008			35,995			36,222			227
208	KOSPI 200 Index	September 2019	South Korean Won		14,476,800			12,220			12,538			318
14	NIKKEI 225 Index	September 2019	Japanese Yen		148,540			1,367			1,378			11
87	SPI 200 Index	September 2019	Australian Dollar		14,266			9,873			10,015			142
35	DAX Index	September 2019	Euro		10,840			12,033			12,326			293
3,547	EURO STOXX 600 Banks Index	September 2019	Euro		23,534			26,504			26,761			257
200	FTSE 100 Index	September 2019	British Pound Sterling		14,738			18,509			18,717			208
													$	2,664
Short
108	Amsterdam Index	July 2019	Euro		12,116		$	13,593		$	13,777		$	(184	)
91	OMXS 30 Index	July 2019	Swedish Krona		14,749			1,552			1,588			(36	)
52	HANG SENG Index	July 2019	Hong Kong Dollar		74,113			9,449			9,488			(39	)
347	MSCI Taiwan Index	July 2019	U.S. Dollar		13,412			13,437			13,412			25
273	10YR Can Bond	September 2019	Canadian Dollar		39,020			29,465			29,797			(332	)
585	FTSE/JSE Top 40 Index	September 2019	South African Rand		306,727			21,908			21,777			131
217	S+P TSE 60 Index	September 2019	Canadian Dollar		42,432			32,319			32,402			(83	)
802	EURO STOXX 50 Index	September 2019	Euro		27,797			30,762			31,608			(846	)
343	MSCI Emerging Markets Index BIC	September 2019	U.S. Dollar		18,066			17,278			18,066			(788	)
1,247	MSCI Mexico Index	September 2019	U.S. Dollar		28,650			29,172			28,650			522
2,372	S&P 500 E Mini Index	September 2019	U.S. Dollar		349,182			343,482			349,182			(5,700	)
69	S&P E Mini Com Ser Index	September 2019	U.S. Dollar		4,458			4,350			4,458			(108	)
143	XAK Technology	September 2019	U.S. Dollar		11,258			10,968			11,258			(290	)
48	XAV Health Care	September 2019	U.S. Dollar		4,471			4,405			4,471			(66	)
204	XAY Cons Discret	September 2019	U.S. Dollar		24,623			24,464			24,623			(159	)
													$	(7,953	)
Total net unrealized appreciation (depreciation) on futures contracts													$	(5,289	)

Centrally Cleared Interest Rate Swap

Floating Rate Reference	Pay/Receive Floating Rate	Fixed Rate	Pay/Receive Payment Frequency	Maturity Date	Cleared Exchange	Notional Amount (in thousands)	Upfront Payment Paid (Received)	Value	Unrealized Appreciation (Depreciation)
SEK 3M STIBOR	Receive	1.330%	1YR/3M	March 2029	LCH	SEK 160,260	$(141)	$(1,406)		$(1,265)

Centrally Cleared Credit Default Swap

Reference Entity

Buy/Sell Protection

Fixed Deal Pay Rate

Payment Frequency

Maturity Date

Cleared Exchange

Notional Amount (in thousands

)

Upfront Payment Paid (Received

)

Value

Unrealized Appreciation (Depreciation)

iTRAXX Europe S31

Sell

1.000%

3M

June 2024

ICE

EUR 16,900

$390

$465

$

75

See accompanying Notes to Financial Statements.

June 30, 2019   William Blair Funds 105

Macro Allocation Fund

Portfolio of Investments, June 30, 2019(all dollar amounts in thousands) (unaudited)

Total Return Swaps

Reference Entity

Pay/ Receive Floating Rate

Floating Rates

Maturity Dates

Counterparty

Notional Amount (in thousands

)

Market Value

Unrealized Appreciation (Depreciation)

Euro-OAT Future

Receive

0 bp

Sep 2019

Credit Suisse International

EUR 69,029

$

(1,184

)

$

(1,184

)

Euro-BUND Future

Receive

0 bp

Sep 2019

Credit Suisse International

EUR 5,122

(68

)

(68

)

10YR T-Note Future

Pay

0 bp

Sep 2019

Credit Suisse International

$57,306

919

919

5YR T-Notes Future

Receive

0 bp

Sep 2019

Credit Suisse International

9,084

(133

)

(133

)

MSCI Emerging Markets India Net Total Return Index

Pay

3 Month LIBOR minus 21 bp

Dec 2019

Goldman Sachs International

15,810

1,773

1,773

MSCI Emerging Markets Indonesia Net Total Return USD

Pay

3 Month LIBOR minus 5 bp

Jun 2020

Citibank N.A.

15,198

2,259

2,259

Swiss Market Index (Total Return)

Receive

3 Month CHF LIBOR minus 20 bp

Sep 2019

Goldman Sachs International

CHF 12,092

31

31

$

3,597

Total net unrealized appreciation (depreciation) on swaps

$

2,407

See accompanying Notes to Financial Statements.

106 Semiannual Report June 30, 2019

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	Growth Fund		Large Cap Growth Fund		Mid Cap Growth Fund
Assets
Investments in securities, at cost	$	170,555	$	159,137	$	56,162
Investments in securities, at value	$	259,985	$	230,644	$	69,297
Receivable for securities sold		—		1,238		328
Receivable for fund shares sold		62		296		39
Receivable from Adviser		1		27		18
Dividend and interest receivable		76		54		16
Total assets		260,124		232,259		69,698
Liabilities
Payable for investment securities purchased		—		1,457		850
Payable for fund shares redeemed		113		244		6
Payable to custodian		6		4		2
Management fee payable		157		110		50
Distribution fee payable		8		11		1
Other payables and accrued expenses		56		31		42
Total liabilities		340		1,857		951
Net assets	$	259,784	$	230,402	$	68,747
Capital
Composition of net assets
Paid in capital	$	148,558	$	147,302	$	48,413
Total distributable earnings (loss)		111,226		83,100		20,334
Net assets	$	259,784	$	230,402	$	68,747
Class N shares
Net assets	$	40,589	$	56,605	$	5,974
Shares outstanding		4,191,446		3,804,408		528,563
Net asset value per share	$	9.68	$	14.88	$	11.30
Class I shares
Net assets	$	219,144	$	173,745	$	62,722
Shares outstanding		19,326,621		11,046,706		5,152,513
Net asset value per share	$	11.34	$	15.73	$	12.17
Class R6 shares
Net assets	$	51	$	52	$	51
Shares outstanding		4,521		3,307		4,191
Net asset value per share	$	11.34	$	15.73	$	12.17

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 107

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	Growth Fund			Large Cap Growth Fund				Mid Cap Growth Fund
Investment income
Dividends	$	1,192			$	1,084			$	241
Less foreign tax withheld		—				—				(1	)
Interest		5				5				2
Total income		1,197				1,089				242
Expenses
Investment advisory fees		929				684				300
Distribution fees		50				62				7
Custodian fees		38				23				20
Transfer agent fees		30				14				6
Sub-transfer agent fees
Class N		24				32				3
Class I		58				59				36
Professional fees		25				22				21
Registration fees		25				21				19
Shareholder reporting fees		8				7				1
Trustee fees		12				7				2
Other expenses		12				11				6
Total expenses before expense limitation		1,211				942				421
Expenses waived or reimbursed by the Adviser		(8	)			(112	)			(109	)
Net expenses		1,203				830				312
Net investment income (loss)		(6	)			259				(70	)
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities		14,964				8,820				5,243
Total net realized gain (loss)		14,964				8,820				5,243
Change in net unrealized appreciation (depreciation) of:
Investments in securities		34,949				34,565				10,069
Change in net unrealized appreciation (depreciation)		34,949				34,565				10,069
Net increase (decrease) in net assets resulting from operations	$	49,907			$	43,644			$	15,242

See accompanying Notes to Financial Statements.

108 Semiannual Report June 30, 2019

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	Growth Fund						Large Cap Growth Fund						Mid Cap Growth Fund
	2019			2018			2019			2018			2019			2018
Operations
Net investment income (loss)	$	(6	)	$	(311	)	$	259		$	86		$	(70	)	$	(180	)
Net realized gain (loss) on investments, and other assets and liabilities		14,964			81,637			8,820			32,604			5,243			13,079
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		34,949			(49,663	)		34,565			(17,587	)		10,069			(12,543	)
Net increase (decrease) in net assets resulting from operations		49,907			31,663			43,644			15,103			15,242			356
Distributions to shareholders from
Class N		—			(12,048	)		—			(6,522	)		—			(982	)
Class I		—			(51,103	)		—			(20,739	)		—			(9,097	)
Class R6		—			—			—			—			—			—
Total distributions		—			(63,151	)		—			(27,261	)		—			(10,079	)
Capital stock transactions
Proceeds from sale of shares		11,310			42,834			32,388			60,009			4,135			10,781
Shares issued in reinvestment of income dividends and capital gain distributions		—			60,277			—			23,837			—			9,695
Less cost of shares redeemed		(27,109	)		(199,681	)		(24,590	)		(96,291	)		(6,747	)		(32,171	)
Net increase (decrease) in net assets resulting from capital share transactions		(15,799	)		(96,570	)		7,798			(12,445	)		(2,612	)		(11,695	)
Increase (decrease) in net assets		34,108			(128,058	)		51,442			(24,603	)		12,630			(21,418	)
Net assets
Beginning of period		225,676			353,734			178,960			203,563			56,117			77,535
End of period	$	259,784		$	225,676		$	230,402		$	178,960		$	68,747		$	56,117

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 109

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	Small-Mid Cap Growth Fund			Small-Mid Cap Value Fund			Small Cap Growth Fund		Small Cap Value Fund
Assets
Investments in securities, at cost		$	2,365,016		$	1,514	$	590,048	$	357,892
Investments in securities, at value		$	2,836,275		$	1,717	$	705,498	$	448,640
Cash			67			—		—		—
Receivable for securities sold			12,391			110		6,946		16,325
Receivable for fund shares sold			3,648			—		1,759		630
Receivable from Adviser			158			10		21		23
Dividend and interest receivable			714			2		203		468
Total assets			2,853,253			1,839		714,427		466,086
Liabilities
Payable for investment securities purchased			7,864			48		5,069		12,494
Payable for fund shares redeemed			3,197			—		537		130
Payable to custodian			—			22		10		5
Management fee payable			2,282			1		625		402
Distribution fee payable			73			—		40		3
Other payables and accrued expenses			476			34		114		115
Total liabilities			13,892			105		6,395		13,149
Net assets		$	2,839,361		$	1,734	$	708,032	$	452,937
Capital
Composition of net assets
Paid in capital		$	2,209,562		$	1,529	$	595,418	$	349,409
Total distributable earnings (loss)			629,799			205		112,614		103,528
Net assets		$	2,839,361		$	1,734	$	708,032	$	452,937
Class N shares
Net assets		$	357,654		$	237	$	198,064	$	16,055
Shares outstanding			13,726,766			21,841		7,165,444		918,192
Net asset value per share		$	26.06		$	10.85	$	27.64	$	17.48
Class I shares
Net assets		$	2,469,870		$	1,487	$	491,045	$	436,832
Shares outstanding			89,725,644			138,001		15,862,359		24,208,335
Net asset value per share		$	27.53		$	10.78	$	30.96	$	18.04
Class R6 shares
Net assets		$	11,837		$	10	$	18,923	$	50
Shares outstanding			429,867			915		611,182		2,749
Net asset value per share		$	27.54		$	10.79	$	30.96	$	18.05

See accompanying Notes to Financial Statements.

110 Semiannual Report June 30, 2019

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	Small-Mid Cap Growth Fund				Small-Mid Cap Value Fund				Small Cap Growth Fund				Small Cap Value Fund
Investment income
Dividends		$	8,066			$	19			$	2,067			$	4,823
Less foreign tax withheld			(60	)			—				(36	)			—
Interest			169				—				50				32
Total income			8,175				19				2,081				4,855
Expenses
Investment advisory fees			13,396				9				3,768				2,737
Distribution fees			467				—				247				21
Custodian fees			27				27				28				26
Transfer agent fees			122				—				39				25
Sub-transfer agent fees
Class N			269				—				128				13
Class I			1,224				—				221				349
Professional fees			106				16				38				34
Registration fees			58				35				38				23
Shareholder reporting fees			140				—				33				15
Trustee fees			85				—				22				22
Other expenses			95				4				27				23
Total expenses before expense limitation			15,989				91				4,589				3,288
Expenses waived or reimbursed by the Adviser			(787	)			(83	)			(59	)			(157	)
Net expenses			15,202				8				4,530				3,131
Net investment income (loss)			(7,027	)			11				(2,449	)			1,724
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities			123,591				50				167				12,260
Redemptions in-kind			40,038				—				—				—
Total net realized gain (loss)			163,629				50				167				12,260
Change in net unrealized appreciation (depreciation) of:
Investments in securities			418,478				221				115,901				63,618
Change in net unrealized appreciation (depreciation)			418,478				221				115,901				63,618
Net increase (decrease) in net assets resulting from operations		$	575,080			$	282			$	113,619			$	77,602

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 111

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	Small-Mid Cap Growth Fund						Small-Mid Cap Value Fund								Small Cap Growth Fund						Small Cap Value Fund
	2019			2018			2019				2018				2019			2018			2019			2018
Operations
Net investment income (loss)	$	(7,027	)	$	(12,353	)		$	11			$	18		$	(2,449	)	$	(4,419	)	$	1,724		$	2,500
Net realized gain (loss) on investments, and other assets and liabilities		163,629			188,474				50				479			167			81,093			12,260			61,842
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		418,478			(287,618	)			221				(852	)		115,901			(111,007	)		63,618			(157,546	)
Net increase (decrease) in net assets resulting from operations		575,080			(111,497	)			282				(355	)		113,619			(34,333	)		77,602			(93,204	)
Distributions to shareholders from
Class N		—			(37,426	)			—				(59	)		—			(23,655	)		—			(2,248	)
Class I		—			(160,129	)			—				(381	)		—			(47,224	)		—			(57,005	)
Class R6		—			—				—				—			—			—			—			—
Total distributions		—			(197,555	)			—				(440	)		—			(70,879	)		—			(59,253	)
Capital stock transactions
Proceeds from sale of shares		497,946			1,291,881				469				488			151,027			326,138			29,774			71,840
Shares issued in reinvestment of income dividends and capital gain distributions		—			193,965				—				439			—			70,242			—			58,395
Less cost of shares redeemed		(637,635	)		(577,832	)			(696	)			(2,096	)		(135,921	)		(201,271	)		(145,954	)		(160,283	)
Net increase (decrease) in net assets resulting from capital share transactions		(139,689	)		908,014				(227	)			(1,169	)		15,106			195,109			(116,180	)		(30,048	)
Increase (decrease) in net assets		435,391			598,962				55				(1,964	)		128,725			89,897			(38,578	)		(182,505	)
Net assets
Beginning of period		2,403,970			1,805,008				1,679				3,643			579,307			489,410			491,515			674,020
End of period	$	2,839,361		$	2,403,970			$	1,734			$	1,679		$	708,032		$	579,307		$	452,937		$	491,515

See accompanying Notes to Financial Statements.

112 Semiannual Report June 30, 2019

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	Global Leaders Fund		International Leaders Fund			International Developed Plus Fund (In Liquidation)				Institutional International Developed Plus Fund (In Liquidation)
Assets
Investments in securities, at cost	$	156,950		$	445,614		$	20,229			$	16,561
Investments in securities, at value	$	211,846		$	546,722		$	24,248			$	20,513
Cash		4			—			23				—
Foreign currency, at value (cost $31; $94; $14; $3)		31			94			14				3
Receivable for securities sold		58			—			—				—
Receivable for fund shares sold		15			683			—				—
Receivable from Adviser		19			32			12				4
Dividend and interest receivable		451			1,488			201				68
Total assets		212,424			549,019			24,498				20,588
Liabilities
Payable for investment securities purchased		2,901			2,664			—				—
Payable for fund shares redeemed		—			77			8,416				—
Payable to custodian		—			3			—				—
Management fee payable		143			367			21				15
Distribution fee payable		2			2			—				—
Foreign capital gains tax liability		—			130			—				—
Other payables and accrued expenses		92			156			50				44
Total liabilities		3,138			3,399			8,487				59
Net assets	$	209,286		$	545,620		$	16,011			$	20,529
Capital
Composition of net assets
Paid in capital	$	153,312		$	446,223		$	(1,470	)		$	16,672
Total distributable earnings (loss)		55,974			99,397			17,481				3,857
Net assets	$	209,286		$	545,620		$	16,011			$	20,529
Class N shares
Net assets	$	8,263		$	10,341		$	1,963			$	—
Shares outstanding		596,915			621,454			119,643				—
Net asset value per share	$	13.84		$	16.64		$	16.41			$	—
Class I shares
Net assets	$	103,148		$	126,671		$	14,048			$	—
Shares outstanding		7,438,720			7,585,393			848,829				—
Net asset value per share	$	13.87		$	16.70		$	16.55			$	—
Institutional/Class R6 shares
Net assets	$	97,875		$	408,608		$	—			$	20,529
Shares outstanding		7,054,845			24,470,592			—				1,425,129
Net asset value per share	$	13.87		$	16.70		$	—			$	14.41

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 113

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	Global Leaders Fund			International Leaders Fund				International Developed Plus Fund (In Liquidation)				Institutional International Developed Plus Fund (In Liquidation)
Investment income
Dividends	$	1,762			$	6,597			$	798			$	253
Less foreign tax withheld		(102	)			(572	)			(65	)			(26	)
Interest		9				33				9				3
Total income		1,669				6,058				742				230
Expenses
Investment advisory fees		894				2,122				296				84
Distribution fees		10				12				2				—
Custodian fees		35				46				30				24
Transfer agent fees		6				9				2				—
Sub-transfer agent fees
Class N		5				7				1				—
Class I		30				35				45				—
Professional fees		31				43				22				19
Registration fees		25				31				16				10
Shareholder reporting fees		2				5				1				—
Trustee fees		7				15				4				1
Other expenses		12				21				6				2
Total expenses before expense limitation		1,057				2,346				425				140
Expenses waived or reimbursed by the Adviser		(94	)			(108	)			(94	)			(56	)
Net expenses		963				2,238				331				84
Net investment income (loss)		706				3,820				411				146
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities, net of foreign taxes, if applicable		1,374				(1,450	)			14,102				2
Foreign currency transactions		(2	)			(30	)			(15	)			—
Total net realized gain (loss)		1,372				(1,480	)			14,087				2
Change in net unrealized appreciation (depreciation) of:
Investments in securities		33,907				86,081				296				3,225
Foreign currency translations		1				(105	)			3				1
Change in net unrealized appreciation (depreciation)		33,908				85,976				299				3,226
Net increase (decrease) in net assets resulting from operations	$	35,986			$	88,316			$	14,797			$	3,374

See accompanying Notes to Financial Statements.

114 Semiannual Report June 30, 2019

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	Global Leaders Fund						International Leaders Fund						International Developed Plus Fund (In Liquidation)						Institutional International Developed Plus Fund (In Liquidation)
	2019			2018			2019			2018			2019			2018			2019				2018
Operations
Net investment income (loss)	$	706		$	813		$	3,820		$	4,623		$	411		$	1,273			$	146			$	233
Net realized gain (loss) on investments, and other assets and liabilities		1,372			28,281			(1,480	)		6,745			14,087			405				2				405
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		33,908			(39,539	)		85,976			(70,725	)		299			(19,925	)			3,226				(3,523	)
Net increase (decrease) in net assets resulting from operations		35,986			(10,445	)		88,316			(59,357	)		14,797			(18,247	)			3,374				(2,885	)
Distributions to shareholders from
Class N		—			(1,089	)		—			(312	)		—			(37	)			—				—
Class I		—			(13,017	)		—			(3,051	)		—			(2,203	)			—				—
Institutional/Class R6		—			(12,002	)		—			(13,274	)		—			—				—				(554	)
Total distributions		—			(26,108	)		—			(16,637	)		—			(2,240	)			—				(554	)
Capital stock transactions
Proceeds from sale of shares		7,933			46,840			68,495			153,690			50			799				2,000				—
Shares issued in reinvestment of income dividends and capital gain distributions		—			25,924			—			15,804			—			2,156				—				554
Less cost of shares redeemed		(5,333	)		(76,860	)		(21,190	)		(62,329	)		(87,417	)		(14,626	)			(1,000	)			(50	)
Net increase (decrease) in net assets resulting from capital share transactions		2,600			(4,096	)		47,305			107,165			(87,367	)		(11,671	)			1,000				504
Increase (decrease) in net assets		38,586			(40,649	)		135,621			31,171			(72,570	)		(32,158	)			4,374				(2,935	)
Net assets
Beginning of period		170,700			211,349			409,999			378,828			88,581			120,739				16,155				19,090
End of period	$	209,286		$	170,700		$	545,620		$	409,999		$	16,011		$	88,581			$	20,529			$	16,155

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 115

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	International Growth Fund			Institutional International Growth Fund		International Small Cap Growth Fund
Assets
Investments in securities, at cost		$	1,748,098	$	1,469,372		$	273,165
Investments in securities, at value		$	2,138,542	$	1,788,374		$	308,843
Foreign currency, at value (cost $1,621; $1,376; $102)			1,621		1,376			102
Receivable for securities sold			32,109		8,828			—
Receivable for fund shares sold			563		173			1,120
Receivable from Adviser			2		—			—
Dividend and interest receivable			7,711		5,841			965
Total assets			2,180,548		1,804,592			311,030
Liabilities
Payable for investment securities purchased			6,494		5,355			2,005
Payable for fund shares redeemed			6,425		135			115
Payable to custodian			16		7			2
Management fee payable			1,770		1,360			257
Distribution fee payable			101		—			1
Other payables and accrued expenses			826		418			196
Total liabilities			15,632		7,275			2,576
Net assets		$	2,164,916	$	1,797,317		$	308,454
Capital
Composition of net assets
Paid in capital		$	1,794,573	$	1,513,110		$	302,294
Total distributable earnings (loss)			370,343		284,207			6,160
Net assets		$	2,164,916	$	1,797,317		$	308,454
Class N shares
Net assets		$	502,011		—		$	3,534
Shares outstanding			18,267,928		—			287,365
Net asset value per share		$	27.48		—		$	12.30
Class I shares
Net assets		$	1,662,854		—		$	158,003
Shares outstanding			59,093,578		—			12,714,685
Net asset value per share		$	28.14		—		$	12.43
Institutional/Class R6 shares
Net assets		$	51	$	1,797,317		$	146,917
Shares outstanding			1,814		112,302,798			11,758,084
Net asset value per share		$	28.14	$	16.00		$	12.49

See accompanying Notes to Financial Statements.

116 Semiannual Report June 30, 2019

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	International Growth Fund				Institutional International Growth Fund				International Small Cap Growth Fund
Investment income
Dividends		$	30,305			$	26,123			$	4,863
Less foreign tax withheld			(2,560	)			(2,219	)			(447	)
Interest			44				57				26
Total income			27,789				23,961				4,442
Expenses
Investment advisory fees			10,797				8,649				1,686
Distribution fees			610				—				4
Custodian fees			132				105				68
Transfer agent fees			87				39				14
Sub-transfer agent fees
Class N			354				—				2
Class I			648				—				91
Professional fees			122				110				50
Registration fees			28				14				27
Shareholder reporting fees			88				6				19
Trustee fees			100				76				19
Other expenses			85				66				21
Total expenses before expense limitation			13,051				9,065				2,001
Expenses waived or reimbursed by the Adviser			(41	)			—				—
Net expenses			13,010				9,065				2,001
Net investment income (loss)			14,779				14,896				2,441
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities, net of foreign taxes, if applicable			238				(14,269	)			(10,667	)
Redemptions in-kind			—				7,223				—
Foreign currency transactions			(836	)			(421	)			(48	)
Total net realized gain (loss)			(598	)			(7,467	)			(10,715	)
Change in net unrealized appreciation (depreciation) of:
Investments in securities			376,087				319,149				67,523
Foreign currency translations			34				12				8
Change in net unrealized appreciation (depreciation)			376,121				319,161				67,531
Net increase (decrease) in net assets resulting from operations		$	390,302			$	326,590			$	59,257

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 117

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	International Growth Fund						Institutional International Growth Fund						International Small Cap Growth Fund
	2019			2018			2019			2018			2019			2018
Operations
Net investment income (loss)	$	14,779		$	22,467		$	14,896		$	21,963		$	2,441		$	3,491
Net realized gain (loss) on investments, and other assets and liabilities		(598	)		132,672			(7,467	)		98,966			(10,715	)		16,217
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		376,121			(661,540	)		319,161			(496,584	)		67,531			(159,626	)
Net increase (decrease) in net assets resulting from operations		390,302			(506,401	)		326,590			(375,655	)		59,257			(139,918	)
Distributions to shareholders from
Class N		—			(39,208	)		—			—			—			(462	)
Class I		—			(145,771	)		—			—			—			(25,473	)
Institutional/Class R6		—			—			—			(186,678	)		—			(21,100	)
Total distributions		—			(184,979	)		—			(186,678	)		—			(47,035	)
Capital stock transactions
Proceeds from sale of shares		191,097			309,595			91,490			268,610			31,067			95,395
Shares issued in reinvestment of income dividends and capital gain distributions		—			172,803			—			180,253			—			40,939
Less cost of shares redeemed		(519,827	)		(826,740	)		(405,198	)		(432,394	)		(122,594	)		(210,410	)
Net increase (decrease) in net assets resulting from capital share transactions		(328,730	)		(344,342	)		(313,708	)		16,469			(91,527	)		(74,076	)
Increase (decrease) in net assets		61,572			(1,035,722	)		12,882			(545,864	)		(32,270	)		(261,029	)
Net assets
Beginning of period		2,103,344			3,139,066			1,784,435			2,330,299			340,724			601,753
End of period	$	2,164,916		$	2,103,344		$	1,797,317		$	1,784,435		$	308,454		$	340,724

See accompanying Notes to Financial Statements.

118 Semiannual Report June 30, 2019

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	Emerging Markets Leaders Fund		Emerging Markets Growth Fund		Emerging Markets Small Cap Growth Fund
Assets
Investments in securities, at cost	$	192,402	$	656,133		$	238,283
Investments in securities, at value	$	223,414	$	801,627		$	277,149
Foreign currency, at value (cost $325; $2,003; $798)		326		2,003			798
Receivable for securities sold		—		17,075			4,360
Receivable for fund shares sold		592		166			217
Receivable from Adviser		23		—			10
Dividend and interest receivable		733		3,092			1,363
Total assets		225,088		823,963			283,897
Liabilities
Payable for investment securities purchased		—		4,449			1,109
Payable for fund shares redeemed		—		13,369			56
Payable to custodian		1		4			6
Management fee payable		196		728			250
Distribution fee payable		—		2			1
Foreign capital gains tax liability		626		2,528			2
Other payables and accrued expenses		202		553			481
Total liabilities		1,025		21,633			1,905
Net assets	$	224,063	$	802,330		$	281,992
Capital
Composition of net assets
Paid in capital	$	197,508	$	668,599		$	296,327
Total distributable earnings (loss)		26,555		133,731			(14,335	)
Net assets	$	224,063	$	802,330		$	281,992
Class N shares
Net assets	$	2,260	$	7,833		$	5,816
Shares outstanding		234,405		607,294			382,521
Net asset value per share	$	9.64	$	12.90		$	15.20
Class I shares
Net assets	$	43,233	$	74,224		$	155,857
Shares outstanding		4,472,033		5,692,732			10,184,514
Net asset value per share	$	9.67	$	13.04		$	15.30
Class R6 shares
Net assets	$	178,570	$	720,273		$	120,319
Shares outstanding		18,491,174		54,754,239			7,847,524
Net asset value per share	$	9.66	$	13.16		$	15.33

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 119

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	Emerging Markets Leaders Fund				Emerging Markets Growth Fund				Emerging Markets Small Cap Growth Fund
Investment income
Dividends		$	2,622			$	10,562			$	2,259
Less foreign tax withheld			(254	)			(838	)			(196	)
Interest			25				25				7
Total income			2,393				9,749				2,070
Expenses
Investment advisory fees			1,170				4,438				1,592
Distribution fees			3				9				8
Custodian fees			43				162				161
Transfer agent fees			6				20				35
Sub-transfer agent fees
Class N			1				3				5
Class I			12				31				69
Professional fees			45				82				112
Registration fees			25				32				33
Shareholder reporting fees			5				3				24
Trustee fees			13				37				15
Other expenses			13				31				18
Total expenses before expense limitation			1,336				4,848				2,072
Expenses waived or reimbursed by the Adviser			(51	)			—				(210	)
Net expenses			1,285				4,848				1,862
Net investment income (loss)			1,108				4,901				208
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities, net of foreign taxes, if applicable			269				2,583				(4,504	)
Foreign currency transactions			(48	)			(438	)			(403	)
Total net realized gain (loss)			221				2,145				(4,907	)
Change in net unrealized appreciation (depreciation) of:
Investments in securities			32,556				111,999				29,568
Foreign currency translations			(594	)			(2,486	)			(6	)
Change in net unrealized appreciation (depreciation)			31,962				109,513				29,562
Net increase (decrease) in net assets resulting from operations		$	33,291			$	116,559			$	24,863

See accompanying Notes to Financial Statements.

120 Semiannual Report June 30, 2019

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	Emerging Markets Leaders Fund						Emerging Markets Growth Fund						Emerging Markets Small Cap Growth Fund
	2019			2018			2019			2018			2019			2018
Operations
Net investment income (loss)	$	1,108		$	2,757		$	4,901		$	4,704		$	208		$	931
Net realized gain (loss) on investments, and other assets and liabilities		221			38,309			2,145			136,983			(4,907	)		(40,803	)
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		31,962			(116,117	)		109,513			(369,221	)		29,562			(81,984	)
Net increase (decrease) in net assets resulting from operations		33,291			(75,051	)		116,559			(227,534	)		24,863			(121,856	)
Distributions to shareholders from
Class N		—			(179	)		—			(966	)		—			(201	)
Class I		—			(3,674	)		—			(11,141	)		—			(4,413	)
Class R6		—			(16,113	)		—			(81,475	)		—			(2,353	)
Total distributions		—			(19,966	)		—			(93,582	)		—			(6,967	)
Capital stock transactions
Proceeds from sale of shares		17,634			45,869			82,724			228,271			49,731			157,577
Shares issued in reinvestment of income dividends and capital gain distributions		—			19,766			—			81,112			—			6,516
Less cost of shares redeemed		(25,776	)		(249,616	)		(137,924	)		(566,109	)		(69,537	)		(222,964	)
Net increase (decrease) in net assets resulting from capital share transactions		(8,142	)		(183,981	)		(55,200	)		(256,726	)		(19,806	)		(58,871	)
Increase (decrease) in net assets		25,149			(278,998	)		61,359			(577,842	)		5,057			(187,694	)
Net assets
Beginning of period		198,914			477,912			740,971			1,318,813			276,935			464,629
End of period	$	224,063		$	198,914		$	802,330		$	740,971		$	281,992		$	276,935

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 121

Statements of Assets and Liabilities

As of June 30, 2019(dollar amounts in thousands) (unaudited)

	Bond Fund			Income Fund			Low Duration Fund			Macro Allocation Fund
Assets
Investments in securities, at cost	$	399,854		$	63,498		$	100,898			$	816,241
Investments in securities, at value	$	413,369		$	63,840		$	100,694			$	864,934
Cash		—			1			—				—
Receivable for securities sold		10,043			3,003			12,013				36,165
Receivable for fund shares sold		382			23			4				537
Receivable for variation margin on centrally cleared swaps		—			—			—				9
Receivable from Adviser		8			3			11				—
Dividend and interest receivable		3,177			373			396				1,859
Unrealized appreciation on swap contracts		—			—			—				4,982
Unrealized appreciation on forward foreign currency contracts		—			—			—				8,544
Total assets		426,979			67,243			113,118				917,030
Liabilities
Security sold, not yet purchased (proceeds $10,043; $3,003; $12,013; $—)		10,086			3,021			12,085				—
Payable for futures variation margin		—			—			—				1,130
Payable for variation margin on centrally cleared swaps		15			—			—				—
Payable for investment securities purchased		—			—			—				7,081
Payable for fund shares redeemed		763			91			721				1,879
Payable to custodian		6			1			1				21
Cash received as collateral, due to broker		—			—			—				3,922
Unrealized depreciation on swap contracts		—			—			—				1,385
Unrealized depreciation on forward foreign currency contracts		—			—			—				10,490
Management fee payable		102			21			25				600
Distribution fee payable		8			3			—				8
Distributions payable to shareholders		162			9			62				—
Other payables and accrued expenses		65			26			31				237
Total liabilities		11,207			3,172			12,925				26,753
Net assets	$	415,772		$	64,071		$	100,193			$	890,277
Capital
Composition of net assets
Paid in capital	$	427,920		$	69,966		$	127,247			$	1,018,440
Total distributable earnings (loss)		(12,148	)		(5,895	)		(27,054	)			(128,163	)
Net assets	$	415,772		$	64,071		$	100,193			$	890,277
Class N shares
Net assets	$	67,493		$	21,319		$	1,632			$	37,918
Shares outstanding		6,541,351			2,483,698			186,407				3,243,490
Net asset value per share	$	10.32		$	8.58		$	8.75			$	11.69
Class I shares
Net assets	$	281,303		$	42,701		$	54,744			$	440,655
Shares outstanding		27,553,950			5,008,512			6,258,559				37,752,463
Net asset value per share	$	10.21		$	8.53		$	8.75			$	11.68
Class R6 shares
Net assets	$	66,976		$	51		$	43,817			$	411,704
Shares outstanding		6,564,107			5,951			5,006,245				35,248,111
Net asset value per share	$	10.20		$	8.53		$	8.75			$	11.68

See accompanying Notes to Financial Statements.

122 Semiannual Report June 30, 2019

Statements of Operations

For the Period Ended June 30, 2019(all amounts in thousands) (unaudited)

	Bond Fund				Income Fund				Low Duration Fund				Macro Allocation Fund
Investment income
Dividends		$	—			$	—			$	—			$	6,216
Interest			7,675				908				1,458				3,118
Total income			7,675				908				1,458				9,334
Expenses
Investment advisory fees			620				123				151				3,679
Distribution fees			50				16				1				54
Custodian fees			36				27				29				60
Transfer agent fees			33				5				4				129
Sub-transfer agent fees
Class N			47				15				1				17
Class I			103				8				9				188
Professional fees			43				20				23				59
Registration fees			31				19				24				38
Shareholder reporting fees			21				3				1				24
Trustee fees			18				3				6				41
Other expenses			22				6				10				93
Total expenses before expense limitation			1,024				245				259				4,382
Expenses waived or reimbursed by the Adviser			(62	)			(12	)			(70	)			—
Net expenses			962				233				189				4,382
Net investment income (loss)			6,713				675				1,269				4,952
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities			(918	)			(183	)			(582	)			29,018
Options			—				—				—				(3,270	)
Futures contracts			—				—				—				(60,739	)
Swaps			(126	)			—				—				(3,756	)
Forward foreign currency contracts			—				—				—				15,943
Foreign currency transactions			—				—				—				(36	)
Total net realized gain (loss)			(1,044	)			(183	)			(582	)			(22,840	)
Change in net unrealized appreciation (depreciation) of:
Investments in securities			27,278				2,207				1,864				58,061
Options			—				—				—				921
Futures contracts			—				—				—				(13,442	)
Swaps			(426	)			—				—				3,621
Forward foreign currency contracts			—				—				—				(7,141	)
Foreign currency translations			—				—				—				67
Change in net unrealized appreciation (depreciation)			26,852				2,207				1,864				42,087
Net increase (decrease) in net assets resulting from operations		$	32,521			$	2,699			$	2,551			$	24,199

See accompanying Notes to Financial Statements.

June 30, 2019 William Blair Funds 123

Statements of Changes in Net Assets

For the Period Ended June 30, 2019(unaudited)and the Year Ended December 31, 2018(all amounts in thousands)

	Bond Fund						Income Fund						Low Duration Fund						Macro Allocation Fund
	2019			2018			2019			2018			2019			2018			2019			2018
Operations
Net investment income (loss)	$	6,713		$	16,661		$	675		$	1,481		$	1,269		$	3,651		$	4,952		$	11,691
Net realized gain (loss) on investments, and other assets and liabilities		(1,044	)		(4,154	)		(183	)		(654	)		(582	)		(1,308	)		(22,840	)		78,431
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		26,852			(25,201	)		2,207			(1,488	)		1,864			(410	)		42,087			(109,906	)
Net increase (decrease) in net assets resulting from operations		32,521			(12,694	)		2,699			(661	)		2,551			1,933			24,199			(19,784	)
Distributions to shareholders from
Class N		(1,394	)		(3,412	)		(358	)		(993	)		(31	)		(62	)		—			(675	)
Class I		(6,014	)		(14,892	)		(709	)		(1,404	)		(1,054	)		(2,632	)		—			(15,790	)
Class R6		(1,504	)		(3,657	)		—			—			(894	)		(3,226	)		—			(13,220	)
Total distributions		(8,912	)		(21,961	)		(1,067	)		(2,397	)		(1,979	)		(5,920	)		—			(29,685	)
Capital stock transactions
Proceeds from sale of shares		36,804			117,343			15,250			10,624			8,500			16,290			176,292			301,576
Shares issued in reinvestment of income dividends and capital gain distributions		7,909			20,114			1,006			2,283			1,564			5,084			—			25,916
Less cost of shares redeemed		(75,096	)		(240,011	)		(11,032	)		(43,412	)		(15,809	)		(145,098	)		(232,032	)		(664,845	)
Net increase (decrease) in net assets resulting from capital share transactions		(30,383	)		(102,554	)		5,224			(30,505	)		(5,745	)		(123,724	)		(55,740	)		(337,353	)
Increase (decrease) in net assets		(6,774	)		(137,209	)		6,856			(33,563	)		(5,173	)		(127,711	)		(31,541	)		(386,822	)
Net assets
Beginning of period		422,546			559,755			57,215			90,778			105,366			233,077			921,818			1,308,640
End of period	$	415,772		$	422,546		$	64,071		$	57,215		$	100,193		$	105,366		$	890,277		$	921,818

See accompanying Notes to Financial Statements.

124 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

(1) Organization

(a) Description of the Trust

William Blair Funds (the “Trust”) is a mutual fund registered under the Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management investment company. The Trust currently consists of the following twenty-one funds (the “Funds”), each with its own investment objective and policies. For each Fund, the number of shares authorized is unlimited.

U.S. Equity Funds	International Equity Funds	Fixed Income Funds
Growth	International Leaders	Bond
Large Cap Growth	International Developed Plus	Income
Mid Cap Growth	Institutional International Developed Plus	Low Duration
Small-Mid Cap Growth	International Growth
Small-Mid Cap Value	Institutional International Growth	Multi-Asset and Alternative Fund
Small Cap Growth	International Small Cap Growth	Macro Allocation
Small Cap Value	Emerging Markets Leaders
Global Equity Fund	Emerging Markets Growth
Global Leaders	Emerging Markets Small Cap Growth

William Blair Investment Management, LLC (the “Adviser”) serves as the Trust’s investment adviser. William Blair & Company, L.L.C. (“WBC” or the “Distributor”), an affiliate of the Adviser, serves as the Trust’s principal underwriter and distributor.

Upon recommendation of the Adviser, the Board of Trustees of the Trust determined that it was in the best interests of the International Developed Plus Fund and the Institutional International Developed Plus Fund to redeem all the shares of the International Developed Plus Fund and the Institutional International Developed Plus Fund on or before September 30, 2019, and then terminate the International Developed Plus Fund and the Institutional International Developed Plus Fund.

(b) Share Classes

Each Fund is comprised of Class N, Class I and Class R6 shares, except the International Developed Plus Fund which is comprised of Class N and Class I shares and the Institutional International Developed Plus Fund and Institutional International Growth Fund.

Effective May 1, 2019, Institutional Class shares of Global Leaders, International Leaders, International Small Cap Growth, Emerging Markets Leaders, Emerging Markets Growth, Emerging Markets Small Cap Growth, Bond, Low Duration and Macro Allocation Funds were redesignated as Class R6 shares. On that same date, the Growth, Large Cap Growth, Mid Cap Growth, Small-Mid Cap Growth, Small-Mid Cap Value, Small Cap Growth, Small Cap Value, International Growth and Income Funds began offering Class R6 shares.

Class Nshares are available to the general public, either directly through the Trust’s distributor or through a select number of financial intermediaries. Class N shares are sold without any sales load and carry an annual 12b-1 distribution fee at a fixed rate (0.25% for the U.S. Equity, Global Equity, International Equity and Multi-Asset and Alternative Funds and 0.15% for the Fixed Income Funds as discussed inNote 4(b) – Transactions with Affiliates – Underwriting Distribution Services and Shareholder Administration Agreements) and a sub-transfer agent fee that is not a fixed rate and varies by Fund and class, as discussed below.

Class Ishares are available to certain retirement and deferred compensation plans, clients of certain financial intermediaries, and asset-based fee advisory clients of William Blair. The minimum initial investment for a Class I account is $500,000, subject to certain exceptions. Class I shares do not carry any sales load or distribution fees and generally have lower ongoing expenses than Class N shares. Class I shares have a sub-transfer agent fee that is not a fixed rate and varies by Fund and class, as discussed below.

Class R6shares are available to certain retirement and deferred compensation plans, clients of certain financial intermediaries, asset-based fee advisory clients of William Blair, and additional types of investors, provided that neither the investor nor the financial intermediary requires the Funds to make any type of servicing or administrative payment. The minimum initial investment for a Class R6 account is $1 million, subject to certain exceptions.

June 30, 2019 William Blair Funds 125

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

Shares of the Institutional International Developed Plus Fund and Institutional International Growth Fund require a minimum initial investment of $5 million, subject to certain exceptions.

Class R6 shares and the Institutional International Developed Plus Fund and the Institutional International Growth Fund do not carry any sales load, distribution fees or sub-transfer agents fees. Class R6 shares of a Fund generally have lower ongoing expenses than the Fund’s Class N and Class I shares.

Sub-transfer agent fees:For Class N and Class I shares, the Funds may reimburse WBC for fees paid to intermediaries such as banks, broker-dealers, financial advisers or other financial institutions for sub-administration, sub-transfer agency and other services provided to investors whose shares of record are held in omnibus, other group accounts, retirement plans or accounts traded through registered securities clearing agents. These fees may vary based on, for example, the nature of services provided, but generally range up to 0.15% of the assets of the class serviced or maintained by the intermediary or up to $15 per sub-account maintained by the intermediary, depending on the method by which the intermediary charges for the services.

(c) Fund Objectives

The investment objectives of the Funds are as follows:

U.S. Equity Funds	Long-term capital appreciation.
Global Equity Fund	Long-term capital appreciation.
International Equity Funds	Long-term capital appreciation.
Bond Fund	Outperform the Bloomberg Barclays U.S. Aggregate Index by maximizing total return through a combination of income and capital appreciation.
Income Fund	High level of current income with relative stability of principal.
Low Duration Fund	Maximize total return. Total return includes both income and capital appreciation.
Macro Allocation Fund	Maximize long-term risk-adjusted total return.

(2) Significant Accounting Policies

The following is a summary of the Trust’s significant accounting policies in effect during the periods covered by the financial statements, which are in accordance with U.S. generally accepted accounting principles (“US GAAP”), which includes the accounting and reporting guidelines under Accounting Standards Topic 946,Financial Services—Investment Companies.

(a) Investment income and transactions

Investment income, realized and unrealized gains and losses, and certain Fund level expenses and expense reductions, if any, are allocated based on the relative net assets of each class, except for certain class specific expenses, which are charged directly to the appropriate class. Differences in class expenses may result in the payment of different per share dividends by class. All share classes of the Funds have equal rights with respect to voting, subject to class specific arrangements.

Dividend income and expenses are recorded on the ex-dividend date, except for those dividends from certain foreign securities that are recorded when the information is available.

Interest income is recorded on an accrual basis, adjusted for amortization of premium or accretion of discount. Variable rate bonds and floating rate notes earn interest at coupon rates that fluctuate at specific time intervals. The interest rates shown in the Portfolio of Investments for the Bond, Income, Low Duration and Macro Allocation Funds were the rates in effect on June 30, 2019. Put bonds may be redeemed at the discretion of the holder on specified dates prior to maturity.

Premiums and discounts are amortized and accreted on a straight-line basis for short-term investments and on an effective interest method for long-term investments.

Paydown gains and losses on mortgage-backed and asset-backed securities are treated as an adjustment to interest income. For the period ended June 30, 2019, the Bond, Income and Low Duration Funds recognized a reduction of interest income and a corresponding increase in net realized gain of $2,180, $391 and $712, respectively (in thousands). This reclassification had no effect on the net increase (decrease) in net assets resulting from operations, net asset value or the net assets of the Funds.

126 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

The Funds do not isolate the portion of operations resulting from fluctuations in foreign currency exchange rates on investments from the fluctuations arising from changes in the value of securities held. Such currency fluctuations are included with the net realized and unrealized gain or loss from investments.

Reported net realized foreign currency gains or losses arise from disposition of foreign currency, the difference in the foreign exchange rates between the trade and settlement dates on securities transactions, and the difference between the amounts of dividends, interest and foreign withholding taxes recorded on the ex-date or accrual date and the U.S. dollar equivalent of the amounts actually received or paid. Net unrealized foreign exchange gains and losses arise from changes (due to the changes in the exchange rate) in the value of foreign currency and other assets and liabilities denominated in foreign currencies held at period end.

For financial reporting purposes, security and shareholder transactions are recorded on trade date in accordance with US GAAP. Realized gains and losses from securities transactions are recognized on a specifically identified cost basis.

Awards from class action litigation may be recorded as a reduction of cost. If the Funds no longer own the applicable securities, the proceeds are recorded as realized gains.

(b) Share Valuation and Distributions to Shareholders

Shares are sold and redeemed on a continuous basis at net asset value. The net asset value per share is determined separately for each class by dividing the Fund’s net assets attributable to that class by the number of shares of the class outstanding as of the close of regular trading on the New York Stock Exchange (the “NYSE”), which is generally 4:00 p.m. Eastern time, on each day the NYSE is open.

Distributions from net investment income, if any, for all Equity and Multi-Asset and Alternative Funds are declared and paid at least annually. Distributions from net investment income for the Fixed Income Funds are declared daily and paid monthly. Capital gain distributions, if any, for all Funds, are declared and paid at least annually in December. Distributions payable to shareholders are recorded on the ex-dividend date.

(c) Foreign Currency Translation

The Funds may invest in securities denominated in foreign currencies. As such, assets and liabilities denominated in foreign currencies are translated into U.S. dollar amounts at the current exchange rate on the date of valuation. The values of foreign investments, open forward foreign currency contracts, and cash denominated in foreign currencies are translated into U.S. dollars using a spot market rate of exchange as of the time of the determination of each Fund’s net asset value, typically 4:00 p.m. Eastern time on days when there is regular trading on the NYSE. Payables and receivables for securities transactions, dividends, interest income and tax reclaims are translated into U.S. dollars using a spot market rate of exchange as of 4:00 p.m. Eastern time. Settlement of purchases and sales and dividend and interest receipts are translated into U.S. dollars using a spot market rate of exchange as of 11:00 a.m. Eastern time.

(d) Income Taxes

Each Fund intends to comply with the provisions of Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”), in order to qualify as regulated investment companies. Each Fund intends to make the requisite distributions of income and capital gains to its shareholders sufficient to relieve it from all, or substantially all, federal income and excise taxes. No provision for federal income and excise taxes has been made.

Certain Funds may be subject to foreign income taxes imposed on realized gains on securities of issuers from certain foreign countries. Such taxes, if applicable, are included within Net realized gain (loss) on transactions from Investments in securities in the Statement of Operations.

Management has evaluated all of the uncertain tax positions of the Funds and has determined that no liability is required to be recorded in the financial statements.

The statute of limitations on the Funds’ tax returns for the prior three years remains open and the returns are subject to examination.

June 30, 2019 William Blair Funds 127

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

Adjustments to the cost of investments for tax purposes may be due to the deferred loss associated with current and prior year wash sales, income recognition from investments in real estate investment trusts and partnerships, and the Funds’ election to mark-to-market their investments in Passive Foreign Investment Companies (“PFICs”). The cost of investments, including derivatives, for federal income tax purposes and related gross unrealized appreciation (depreciation) and net unrealized appreciation/(depreciation) at June 30, 2019, were as follows (in thousands):

Fund	Cost of Investments		Gross Unrealized Appreciation		Gross Unrealized Depreciation		Net Unrealized Appreciation/ (Depreciation)
Growth	$	171,370	$	93,271	$	4,656	$	88,615
Large Cap Growth		159,599		73,939		2,894		71,045
Mid Cap Growth		56,422		14,563		1,688		12,875
Small-Mid Cap Growth		2,378,453		528,220		70,398		457,822
Small-Mid Cap Value		1,562		201		46		155
Small Cap Growth		593,579		139,490		27,571		111,919
Small Cap Value		361,036		100,332		12,728		87,604
Global Leaders		157,963		56,325		2,442		53,883
International Leaders		450,189		99,795		3,262		96,533
International Developed Plus		20,311		3,939		2		3,937
Institutional International Developed Plus		16,569		3,984		40		3,944
International Growth		1,762,985		404,208		28,651		375,557
Institutional International Growth		1,478,763		334,632		25,021		309,611
International Small Cap Growth		279,615		44,584		15,356		29,228
Emerging Markets Leaders		195,215		32,682		4,483		28,199
Emerging Markets Growth		654,959		152,114		5,446		146,668
Emerging Markets Small Cap Growth		245,163		37,077		5,091		31,986
Bond		400,066		16,287		3,177		13,110
Income		63,506		936		620		316
Low Duration		100,899		569		846		(277	)
Macro Allocation		828,501		53,955		22,351		31,604

In addition, the Funds may periodically record reclassifications among certain capital accounts to reflect differences between financial reporting and income tax basis distributions. The reclassifications were reported in order to reflect the tax treatment for certain permanent differences that exist between income tax regulations and US GAAP. The reclassifications generally relate to the tax treatment of net operating losses, expiration of capital loss carryforwards, redemptions in-kind, and utilization of earnings and profits distributed to shareholders on redemption of shares. These reclassifications have no impact on the net asset values or the net assets of the Funds. Accordingly, at December 31, 2018 (the Funds’ most recent fiscal year end), the following reclassifications were recorded (in thousands):

128 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

Fund	Paid in Capital			Total Distributable Earnings (Loss)
Growth	$	19,805		$	(19,805	)
Large Cap Growth		5,048			(5,048	)
Mid Cap Growth		2,417			(2,417	)
Small-Mid Cap Growth		31,047			(31,047	)
Small-Mid Cap Value		98			(98	)
Small Cap Growth		12,551			(12,551	)
Small Cap Value		6,948			(6,948	)
Global Leaders		4,894			(4,894	)
International Leaders		—			—
International Developed Plus		—			—
Institutional International Developed Plus		(11	)		11
International Growth		18			(18	)
Institutional International Growth		—			—
International Small Cap Growth		(274	)		274
Emerging Markets Leaders		24,198			(24,198	)
Emerging Markets Growth		32,994			(32,994	)
Emerging Markets Small Cap Growth		(3,217	)		3,217
Bond		—			—
Income		—			—
Low Duration		(955	)		955
Macro Allocation		—			—

The timing and characterization of certain income and capital gain distributions are determined annually in accordance with federal income tax regulations that may differ from US GAAP. As a result, net investment income or loss and net realized gain or loss for a reporting period may differ from the amount distributed during such period.

Distributions from net realized gains for book purposes may include short-term capital gains, which are included as ordinary income for tax purposes. The tax character of distributions paid during 2018 and 2017 was as follows (in thousands):

	Distributions Paid in 2018								Distributions Paid in 2017
	Ordinary Income				Long-Term Capital Gains				Ordinary Income				Long-Term Capital Gains
Fund	Class N		Class I		Class N		Class I		Class N		Class I		Class N		Class I
Growth	$	815	$	3,461	$	11,233	$	47,642	$	351	$	3,113	$	10,311	$	80,701
Large Cap Growth		503		1,744		6,019		18,995		—		—		146		993
Mid Cap Growth		—		—		982		9,097		—		—		986		10,476
Small-Mid Cap Growth		576		2,467		36,850		157,662		—		—		11,906		81,736
Small-Mid Cap Value		11		75		47		307		—		12		28		320
Small Cap Growth		2,543		5,077		21,112		42,147		4,158		8,754		19,362		40,764
Small Cap Value		—		1,274		2,248		55,731		46		2,095		2,057		45,472
Global Leaders		107		1,617		982		11,400		71		739		215		1,738
International Leaders		37		672		275		2,379		117		844		71		437
International Developed Plus		23		1,522		14		681		55		2,202		—		—
International Growth		2,365		19,058		36,843		126,713		9,771		36,754		—		—
International Small Cap Growth		61		4,260		402		21,212		121		8,233		425		23,214

June 30, 2019 William Blair Funds 129

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

	Distributions Paid in 2018								Distributions Paid in 2017
	Ordinary Income				Long-Term Capital Gains				Ordinary Income				Long-Term Capital Gains
Fund	Class N		Class I		Class N		Class I		Class N		Class I		Class N		Class I
Emerging Markets Leaders	$	15	$	477	$	164	$	3,197	$	12	$	327		$ —	$	—
Emerging Markets Growth		69		1,152		897		9,989		77		1,188		—		—
Emerging Markets Small Cap Growth		—		303		201		4,110		391		8,028		35		651
Bond		3,412		14,892		—		—		3,978		14,049		—		—
Income		993		1,404		—		—		1,426		1,849		—		—
Low Duration		62		2,632		—		—		96		4,594		—		—
Macro Allocation		675		15,790		—		—		260		8,252		—		—

	Distributions Paid in 2018				Distributions Paid in 2017
	Ordinary Income		Long-Term Capital Gains		Ordinary Income		Long-Term Capital Gains
	Institutional/ Class R6		Institutional/ Class R6		Institutional/ Class R6		Institutional/ Class R6
Global Leaders	$	1,539	$	10,463	$	1,836	$	4,097
International Leaders		3,148		10,126		4,501		2,201
Institutional International Developed Plus		554		—		212		—
Institutional International Growth		20,298		166,380		54,743		39,224
International Small Cap Growth		3,872		17,228		6,246		17,011
Emerging Markets Leaders		2,228		13,885		3,069		—
Emerging Markets Growth		9,103		72,372		11,908		—
Emerging Markets Small Cap Growth		257		2,096		4,880		389
Bond		3,657		—		3,890		—
Low Duration		3,226		—		2,290		—
Macro Allocation		13,220		—		6,654		—

As of December 31, 2018, the components of distributable earnings on a tax basis were as follows (in thousands):

Fund	Undistributed Ordinary Income		Accumulated Capital and Other Losses			Undistributed Long-Term Capital Gain		Net Unrealized Appreciation/ (Depreciation)				Total
Growth	$	876	$	—		$	6,732	$	53,711		$	61,319
Large Cap Growth		86		(924	)		3,728		36,566			39,456
Mid Cap Growth		50		—			2,260		2,782			5,092
Small-Mid Cap Growth		—		—			8,545		46,174			54,719
Small-Mid Cap Value		5		(32	)		—		(50	)		(77	)
Small Cap Growth		—		(7,883	)		11,445		(4,567	)		(1,005	)
Small Cap Value		487		—			2,276		23,163			25,926
Global Leaders		70		(719	)		1,532		19,105			19,988
International Leaders		354		(32	)		—		10,759			11,081
International Developed Plus		—		(854	)		—		3,538			2,684
Institutional International Developed Plus		—		(226	)		—		709			483
International Growth		16,855		(39,676	)		—		2,862			(19,959	)
Institutional International Growth		—		(33,348	)		—		(9,035	)		(42,383	)
International Small Cap Growth		—		(15,671	)		—		(37,426	)		(53,097	)
Emerging Markets Leaders		1,130		(3,768	)		—		(4,098	)		(6,736	)
Emerging Markets Growth		4,115		(6,519	)		—		19,576			17,172
Emerging Markets Small Cap Growth		—		(38,594	)		—		(604	)		(39,198	)
Bond		353		(22,047	)		—		(13,975	)		(35,669	)
Income		15		(5,656	)		—		(1,882	)		(7,523	)
Low Duration		61		(25,492	)		—		(2,140	)		(27,571	)
Macro Allocation		16,690		(150,674	)		—		(18,378	)		(152,362	)

130 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

As of December 31, 2018, the Funds may have unused capital loss carryforwards available for federal income tax purposes to be applied against future capital gains, if any. Under current law, the Funds may carry forward net capital losses indefinitely to use to offset capital gains realized in future years. The following table details the Funds’ available capital loss carryforwards as of December 31, 2018, the capital loss carryforwards utilized by the Funds in 2018, and the capital loss carryforwards that expired in 2018 (in thousands):

	Available Capital Loss Carryforwards						Capital Loss Carryforwards		Capital Loss Carryforwards
Fund	Short Term		Long Term		Total		Utilized in 2018		Expired in 2018
Institutional International Developed Plus	$	91	$	—	$	91	$	122	$	—
Emerging Markets Growth		—		—		—		21,948		—
Emerging Markets Small Cap Growth		38,594		—		38,594		—		—
Bond		10,433		11,614		22,047		—		—
Income		2,100		3,556		5,656		—		—
Low Duration		11,653		13,839		25,492		—		955
Macro Allocation		150,674		—		150,674		67,739		—

In order to meet certain excise tax distribution requirements, the Funds are required to measure and distribute annually, net capital gains realized during a twelve month period ending October 31 and net investment income earned during a twelve month period ending December 31. In connection with this, the Funds are permitted for tax purposes to defer into their next fiscal year qualified late year losses. Qualified late year capital losses are any short term or long term capital losses incurred between November 1 and the end of their fiscal year, December 31, 2018. Qualified late year ordinary losses are comprised of losses related to foreign currency and PFICs incurred between November 1 and the end of their fiscal year, December 31, 2018.

As of December 31, 2018, the following Funds deferred, on a tax basis, qualified late year losses of (in thousands):

	Qualified Late Year Losses
Fund	Ordinary Income		Net Capital
Large Cap Growth	$	—	$	924
Small-Mid Cap Value		—		32
Small Cap Growth		—		7,883
Global Leaders		—		719
International Leaders		—		32
International Developed Plus		120		734
Institutional International Developed Plus		26		109
International Growth		—		39,676
Institutional International Growth		1,197		32,151
International Small Cap Growth		2,349		13,322
Emerging Markets Leaders		—		3,768
Emerging Markets Growth		—		6,519

(e) Repurchase Agreements

In a repurchase agreement, a Fund buys a security at one price and at the time of sale, the seller agrees to repurchase the security at a mutually agreed upon time and price (usually within seven days). The repurchase agreement thereby determines the yield during the purchaser’s holding period, while the seller’s obligation to repurchase is secured by the value of the underlying collateral. The Adviser monitors, on an ongoing basis, the value of the underlying collateral to ensure that the value always equals or exceeds the repurchase price plus accrued interest. Repurchase agreements may involve certain risks in the event of a default or insolvency of the other party to the agreement, including possible delays or restrictions upon a Fund’s ability to dispose of the underlying collateral. The risk to a Fund is limited to the ability of the seller to pay the agreed upon sum on the delivery date. In the event of default, a repurchase agreement provides that a Fund is entitled to sell the underlying collateral. The loss, if any, to a Fund will be the difference between the proceeds from the sale and the repurchase price. However, if bankruptcy proceedings are commenced with respect to the seller of the security, disposition of the collateral by the Fund may be delayed or limited. The Funds have master repurchase agreements which allow the Funds to offset amounts owed to a counterparty with amounts owed from the same counterparty, including any collateral, in the event the counterparty defaults. As of June 30, 2019, each Fund’s outstanding repurchase agreements, if any, and related collateral, are shown on the Fund’s Portfolio of Investments. Although no definitive creditworthiness criteria are used, the Adviser reviews the creditworthiness of the banks and non-bank dealers with which a Fund

June 30, 2019 William Blair Funds 131

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

enters into repurchase agreements to evaluate those risks. A Fund may, for tax purposes, deem repurchase agreements collateralized by U.S. Government securities to be investments in U.S. Government securities.

(f) TBA Securities

The Fixed Income Funds may invest in mortgage pass-through securities eligible to be sold in the “to-be announced” market (“TBAs”). TBAs provide for the forward or delayed delivery of the underlying instrument with settlement in up to 180 days. The term TBA comes from the fact that the specific mortgage-backed security that will be delivered to fulfill a TBA trade is not designated at the time the trade is made, but rather is generally announced 48 hours before the settlement date. A Fund generally has the ability to close out a TBA obligation on or before the settlement date, rather than take delivery of the security. When a Fund sells TBAs, it incurs risks similar to those incurred in short sales. For example, when a Fund sells TBAs without owning or having the right to obtain the deliverable securities it incurs a risk of loss because it could have to purchase the securities at a price that is higher than the price at which it sold the securities.

(g) Securities Sold, Not Yet Purchased

A Fund may sell a security it does not own (known as selling a security short) in anticipation of a decline in the fair value of that security. When a Fund sells a security short, it must borrow the security sold short and deliver it to the broker through which it made the short sale. A gain, limited to the price at which the fund sold the security short, or a loss, unlimited in size, will be recognized upon the termination of the short sale. A Fund is also subject to the risk that it may be unable to acquire a security to terminate a short position except at a price substantially in excess of the price at which it sold the security short.

(h) Use of Estimates

The preparation of financial statements in conformity with US GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements. Actual results may differ from those estimates.

(i) Indemnification

In the normal course of business, the Funds have entered into contracts in which the Funds agree to indemnify the other party or parties against various potential costs or liabilities. The Funds’ maximum exposure under these arrangements is unknown. No claim has been made for indemnification pursuant to any such agreement of the Funds.

(j) Redemption In-Kind

In accordance with the Trust’s prospectus, the Funds may distribute portfolio securities rather than cash as payment for a redemption of Fund shares (in-kind redemption). For financial reporting purposes, the Fund recognizes a gain or loss on the transfer of securities depending on the value of those securities on the date of redemption. Gains and losses realized on in-kind redemptions may not be recognized for tax purposes and are reclassified from accumulated net realized gain (loss) to capital paid in excess of par value. During the period ended June 30, 2019, the Small-Mid Cap Growth and Institutional International Growth Funds redeemed $122,137 and $50,390 (in thousands), respectively, of Fund shares in-kind rather than with cash and recognized net realized gains of $40,038 and $7,223 (in thousands), respectively, on the securities distributed to shareholders.

(k) Recent Accounting Pronouncements

In March 2017, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update 2017-08 –Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities(“ASU 2017-08”). ASU 2017-08 changes the amortization of premium on certain debt securities with explicit noncontingent call features that are callable at fixed prices on preset dates by reducing the amortization period from maturity date to the earliest date a bond could be called. As of June 30, 2019, the Funds have adopted ASU 2017-08, which did not have a material impact on the financial statements, and had no effect on the net increase (decrease) in net assets resulting from operations, net asset value or the net assets of the Funds.

(3) Valuation

(a) Investment Valuation

The value of U.S. equity securities, including exchange-traded funds, is determined by valuing securities traded on national securities markets or in the over-the-counter markets at the last sale price or, if applicable, the official closing price or, in the absence of a recent sale on the date of determination, at the mean between the last reported bid and ask prices.

132 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

The value of foreign equity securities is generally determined based upon the last sale price on the foreign exchange or market on which it is primarily traded and in the currency of that market as of the close of the appropriate exchange or, if there have been no sales during that day, at the mean between the last reported bid and ask prices. The Board of Trustees has determined that the passage of time between when the foreign exchanges or markets close and when the Funds compute their net asset values could cause the value of foreign equity securities to no longer be representative or accurate and, as a result, may necessitate that such securities be fair valued. Accordingly, for foreign equity securities, the Funds may use an independent pricing service to fair value price the security as of the close of regular trading on the NYSE. As a result, a Fund’s value for a foreign security may be different from the last sale price (or the mean between the last reported bid and ask prices). As of June 30, 2019, fair valuation estimates for foreign equity securities were not obtained.

Fixed income securities are generally valued using evaluated prices provided by an independent pricing service. The evaluated prices are formed using various market inputs that the pricing service believes accurately represent the market value of a security at a particular point in time. The pricing service determines evaluated prices for fixed income securities using inputs including, but not limited to, recent transaction prices for such securities, dealer quotes, transaction prices for other securities with similar characteristics, collateral characteristics, credit quality, payment history, liquidity and market conditions.

Repurchase agreements and commercial paper are valued at cost, which approximates fair value.

Option contracts on securities, currencies and other financial instruments traded on one or more exchanges are valued at their most recent sale price on the exchange on which they are traded most extensively. Option contracts on foreign indices are valued at the settlement price. If there were no sales that day or if no settlement price is available, such option contracts are valued at the mean between the last reported bid and ask prices. Option contracts traded in the Over-the-Counter (“OTC”) market shall be valued by an independent pricing service. Futures contracts are valued at the most recent settlement price on the exchange on which they are traded most extensively, or if no settlement price is available, at the last sale price as of the close of the exchange. Forward foreign currency contracts are valued on the basis of the value of the underlying currencies at the prevailing currency exchange rate as supplied by an independent pricing service.

Swaps that are centrally cleared through an exchange are valued at the most recent settlement price provided by the exchange on which they are cleared. Total return swaps on equities, equity baskets, indices and other financial instruments are valued by an independent pricing service, or if unavailable, based on the security’s or instrument’s underlying reference asset. All other swap contracts are valued by an independent pricing service. Depending on the product and the terms of the transaction, the independent pricing service may use a series of techniques, including simulation pricing models. The pricing models use inputs that are observed from actively quoted markets such as issuer details, indices, spreads, interest rates, yield curves, dividends and exchange rates.

Securities, and other assets, for which a market price is not available or is deemed unreliable (e.g., securities affected by unusual or extraordinary events, such as natural disasters or securities affected by market or economic events, such as bankruptcy filings), or the value of which is affected by a significant valuation event, are valued at a fair value as determined in good faith by, or under the direction of, the Board of Trustees and in accordance with the Valuation Procedures approved by the Board of Trustees. The value of these fair valued securities may be different from the last sale price (or the mean between the last reported bid and ask prices), and there is no guarantee that a fair valued security will be sold at the price at which a Fund is carrying the security.

(b) Fair Value Measurements

Fair value is defined as the price that a Fund would receive upon selling a security in an orderly transaction to an independent buyer in the principal or most advantageous market for the investment. Various inputs are used in determining the value of a Fund’s investments. A three-tier hierarchy of inputs is used to classify fair value measurements for disclosure purposes. The three-tier hierarchy of inputs is summarized in the three broad levels listed below:

• Level 1—Quoted prices (unadjusted) in active markets for an identical security.

• Level 2—Prices determined using other significant observable inputs. Observable inputs are inputs that other market participants would use in pricing a security. These may include quoted prices for similar securities, interest rates, prepayment speeds, credit risk, and others. In addition, other observable inputs such as foreign exchange rates, benchmark securities indices and foreign futures contracts may be utilized in the valuation of certain foreign securities when significant events occur between the last sale on the foreign securities exchange and the time at which the net asset value of the Fund is calculated.

• Level 3—Prices determined using significant unobservable inputs. In situations where quoted prices or observable inputs are unavailable (for example, when there is little or no market activity for an investment), unobservable inputs may be used. Unobservable inputs reflect the Fund’s own assumptions about the factors market participants would use in pricing an investment, and are based on the best information available.

June 30, 2019 William Blair Funds 133

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

The inputs or methodology used for valuing an investment are not necessarily an indication of the risk associated with investing in those securities.

A description of the valuation methodologies applied to the Funds’ major categories of assets and liabilities measured at fair value on a recurring basis is as follows:

Exchange-Traded Securities

Securities traded on a national securities exchange (or reported on the NASDAQ national market), including exchange-traded funds, are stated at the last reported sales price on the day of valuation. Other securities traded in the over-the-counter market and listed securities for which no sale was reported on that date are stated at the mean between the last reported bid and ask prices. To the extent these securities are actively traded and valuation adjustments are not applied, they are categorized as Level 1 of the fair value hierarchy. Securities traded on inactive markets or valued by reference to similar instruments are generally categorized as Level 2 of the fair value hierarchy.

Fixed Income Securities

Fixed income securities including corporate, convertible and municipal bonds and notes, U.S. government agency obligations, U.S. treasury obligations, sovereign issues, bank loans, convertible preferred securities, asset-backed securities and non-U.S. bonds are generally valued using evaluated prices provided by an independent pricing service. The evaluated prices are formed using various market inputs that the pricing service believes accurately represent the fair value of a security at a particular point in time. The pricing service determines evaluated prices for fixed income securities using inputs including, but not limited to, recent transaction prices for such securities, dealer quotes, transaction prices for other securities with similar characteristics, collateral characteristics, credit quality, payment history, liquidity and market conditions. Securities that use similar valuation techniques and observable inputs as described above are categorized as Level 2 of the fair value hierarchy.

Short-Term Investments

Repurchase agreements and commercial paper are valued at cost, which approximates fair value. These investments are categorized as Level 2 of the fair value hierarchy.

Derivative Instruments

Listed derivatives, such as certain options and futures contracts, that are actively traded are valued based on quoted prices from the exchange on which they are traded most extensively and are categorized as Level 1 of the fair value hierarchy. OTC derivative contracts include forward foreign currency contracts, swap and certain option contracts related to interest rates, foreign currencies, the credit standing of reference entities, equity prices, or commodity prices. Depending on the product and the terms of the transaction, the fair value of OTC derivative products can be modeled by independent pricing services taking into account the counterparties’ creditworthiness and using a series of techniques, including simulation models. Many pricing models do not entail material subjectivity because the methodologies employed do not necessitate significant judgments and the pricing inputs are observed from actively quoted markets, as is the case of forward foreign currency contracts and interest rate swaps. A substantial majority of OTC derivative products valued by a Fund using pricing models fall into this category and are categorized as Level 2 of the fair value hierarchy.

134 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

As of June 30, 2019, the value of securities and other assets, segregated by their hierarchical input levels used in determining fair value and by security class or other financial instruments, are shown below (in thousands).

Investments in securities							Growth			Large Cap Growth			Mid Cap Growth
Level 1—Quoted prices
Common Stocks								$	258,225		$	227,841		$	68,372
Level 2—Other significant observable inputs
Short-Term Investments									1,760			2,803			925
Level 3—Significant unobservable inputs
None									—			—			—
Total investments in securities								$	259,985		$	230,644		$	69,297
Investments in securities				Small-Mid Cap Growth			Small-Mid Cap Value			Small Cap Growth			Small Cap Value
Level 1—Quoted prices
Common Stocks					$	2,778,249		$	1,717		$	694,086		$	442,230
Level 2—Other significant observable inputs
Short-Term Investments						58,026			—			11,412			6,410
Level 3—Significant unobservable inputs
None						—			—			—			—
Total investments in securities					$	2,836,275		$	1,717		$	705,498		$	448,640
Investments in securities	Global Leaders			International Leaders			International Developed Plus			Institutional International Developed Plus			International Growth
Level 1—Quoted prices
Common Stocks		$	207,081		$	529,004		$	22,202		$	18,753		$	2,115,755
Rights			—			381			—			—			479
Level 2—Other significant observable inputs
Common Stocks			—			—			—			—			11,542
Short-Term Investments			4,765			17,337			2,046			1,760			10,766
Level 3—Significant unobservable inputs
None			—			—			—			—			—
Total investments in securities		$	211,846		$	546,722		$	24,248		$	20,513		$	2,138,542
Investments in securities	Institutional  International  Growth			International  Small Cap  Growth			Emerging  Markets  Leaders			Emerging  Markets  Growth			Emerging  Markets  Small Cap  Growth
Level 1—Quoted prices
Common Stocks		$	1,764,526		$	292,815		$	206,136		$	746,662		$	265,633
Preferred Stocks			—			—			—			13,645			2,138
Rights			396			—			—			—			—
Level 2—Other significant observable inputs
Common Stocks			9,604			2,748			8,195			26,557			9,154
Short-Term Investments			13,848			13,280			9,083			14,763			224
Level 3—Significant unobservable inputs
None			—			—			—			—			—
Total investments in securities		$	1,788,374		$	308,843		$	223,414		$	801,627		$	277,149

June 30, 2019 William Blair Funds 135

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

Investments in securities	Bond			Income				Low Duration				Macro Allocation
Assets
Level 1—Quoted Prices
Exchange-Traded Funds	$	—			$	—			$	—			$	568,290
Level 2—Other significant observable inputs
Asset-Backed Securities		6,589				2,823				12,030				—
Commercial Paper		7,000				1,200				1,500				—
Corporate Obligations		183,475				22,687				33,360				—
Foreign Government Bond		—				—				—				20,759
Short-Term Investments		1,083				1,878				731				66,869
U.S. Government and U.S. Government Agency		215,222				35,252				53,073				209,016
Level 3—Significant unobservable inputs
None		—				—				—				—
Liabilities
Level 1—Quoted Prices
None		—				—				—				—
Level 2—Other significant observable inputs
None		—				—				—				—
Level 3—Significant unobservable inputs
None		—				—				—				—
Total investments in securities	$	413,369			$	63,840			$	100,694			$	864,934
Other financial instruments
Assets
Level 1—Quoted Prices
Futures Contracts	$	—			$	—			$	—			$	3,354
Level 2—Other significant observable inputs
Forward Foreign Currency Contracts		—				—				—				8,544
Swaps		(150	)			—				—				5,057
Level 3—Significant unobservable inputs
None		—				—				—				—
Liabilities
Level 1—Quoted Prices
Futures Contracts		—				—				—				(8,643	)
Level 2—Other significant observable inputs
Forward Foreign Currency Contracts		—				—				—				(10,490	)
Swaps		—				—				—				(2,650	)
U.S. Government Agency		(10,086	)			(3,021	)			(12,085	)			—
Level 3—Significant unobservable inputs
None		—				—				—				—
Total Other Financial Instruments	$	(10,236	)		$	(3,021	)		$	(12,085	)		$	(4,828	)

Level 1 Common Stocks are exchange-traded securities with a quoted price. See Portfolio of Investments for Sector Classification.

136 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

(4) Transactions with Affiliates

(a) Management and Expense Limitation Agreements

Each Fund has a management agreement with the Adviser for investment management, clerical, bookkeeping and administrative services. Each Fund pays the Adviser an annual management fee, which is accrued daily and paid monthly, based on a specified percentage of the Fund’s average daily net assets. Each Fund’s annual management fee rate is as follows:

U.S. Equity Funds
Growth	0.75	%
Large Cap Growth2	0.60	%
Mid Cap Growth3	0.90	%
Small-Mid Cap Growth	1.00	%
Small-Mid Cap Value4	0.95	%
Small Cap Growth	1.10	%
Small Cap Value	1.10	%
Fixed Income Funds
Bond	0.30	%
Income1:
First $250 million	0.25	%
In excess of $250 million	0.20	%
Low Duration	0.30	%
Multi-Asset and Alternative Fund
Macro Allocation	0.80	%
Global Equity Fund
Global Leaders5	0.85	%

International Equity Funds
International Leaders6	0.85	%
International Developed Plus	0.90	%
Institutional International Developed Plus:
First $500 million	0.90	%
Next $500 million	0.85	%
In excess of $1 billion	0.80	%
International Growth:
First $250 million	1.10	%
Next $2.25 billion	1.00	%
Next $2.5 billion	0.975	%
Next $5 billion	0.95	%
Next $5 billion	0.925	%
In excess of $15 billion	0.90	%
Institutional International Growth:
First $500 million	1.00	%
Next $500 million	0.95	%
Next $1.5 billion	0.90	%
Next $2.5 billion	0.875	%
Next $5 billion	0.85	%
Next $5 billion	0.825	%
In excess of $15 billion	0.80	%
International Small Cap Growth	1.00	%
Emerging Markets Leaders	1.10	%
Emerging Markets Growth	1.10	%
Emerging Markets Small Cap Growth	1.10	%

1	Management fee also includes a charge of 5% of gross income.
2	Prior to May 1, 2019, the Large Cap Growth Fund paid a management fee at a rate of 0.70% of the Fund’s average daily net assets. Effective May 1, 2019, the management fee paid to the Adviser was reduced to 0.60%.
3	Prior to May 1, 2019, the Mid Cap Growth Fund paid a management fee at a rate of 0.95% of the Fund’s average daily net assets. Effective May 1, 2019, the management fee paid to the Adviser was reduced to 0.90%.
4	Prior to May 1, 2019, the Small-Mid Cap Value Fund paid a management fee at a rate of 1.00% of the Fund’s average daily net assets. Effective May 1, 2019, the management fee paid to the Adviser was reduced to 0.95%.
5	Prior to May 1, 2019, the Global Leaders Fund paid a management fee at a rate of 0.95% of the Fund’s average daily net assets. Effective May 1, 2019, the management fee paid to the Adviser was reduced to 0.85%.
6	Prior to May 1, 2019, the International Leaders Fund paid a management fee at a rate of 0.90% of the Fund’s average daily net assets. Effective May 1, 2019, the management fee paid to the Adviser was reduced to 0.85%.

June 30, 2019 William Blair Funds 137

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

The Funds have also entered into an Amended and Restated Expense Limitation Agreement with the Adviser. Under the terms of the agreement, the Adviser will waive its management fee and/or reimburse a Fund for certain operating expenses, subject to certain excluded expenses, in excess of the agreed upon rate through April 30, 2020. The amount the Adviser owes a Fund as of the reporting date is recorded as Receivable from Adviser in the Statements of Assets and Liabilities. The Adviser reimburses the Funds on a monthly basis. The Adviser will waive fees and/or reimburse expenses to the extent that the total operating expenses for the stated class of the Funds, subject to certain excluded expenses, exceed the following rates (as a percentage of average daily net assets):

	Class N						Class I						Class R6/Institutional Class
Fund	Effective May 1, 2019 through April 30, 2020			Effective May 1, 2018 through April 30, 2019			Effective May 1, 2019 through April 30, 2020			Effective May 1, 2018 through April 30, 2019			Effective May 1, 2019 through April 30, 2020			Effective May 1, 2018 through April 30, 2019
Growth		1.20	%		1.20	%		0.95	%		0.95	%		0.90	%		N/A
Large Cap Growth		0.90	%		1.05	%		0.65	%		0.80	%		0.60	%		N/A
Mid Cap Growth		1.20	%		1.20	%		0.95	%		0.95	%		0.90	%		N/A
Small-Mid Cap Growth		1.35	%		1.35	%		1.10	%		1.10	%		1.05	%		N/A
Small-Mid Cap Value		1.25	%		1.25	%		1.00	%		1.00	%		0.95	%		N/A
Small Cap Growth		1.50	%		1.50	%		1.25	%		1.25	%		1.20	%		N/A
Small Cap Value		1.50	%		1.50	%		1.25	%		1.25	%		1.20	%		N/A
Global Leaders		1.15	%		1.30	%		0.90	%		1.05	%		0.85	%		1.00	%
International Leaders		1.15	%		1.25	%		0.90	%		1.00	%		0.85	%		0.95	%
International Developed Plus		1.25	%		1.25	%		1.00	%		1.00	%		N/A			N/A
Institutional International Developed Plus		N/A			N/A			N/A			N/A			0.90	%		0.90	%
International Growth		1.45	%		1.45	%		1.20	%		1.20	%		1.15	%		N/A
Institutional International Growth		N/A			N/A			N/A			N/A			1.05	%		1.05	%
International Small Cap Growth		1.55	%		1.55	%		1.30	%		1.30	%		1.25	%		1.25	%
Emerging Markets Leaders		1.40	%		1.55	%		1.15	%		1.30	%		1.10	%		1.25	%
Emerging Markets Growth		1.60	%		1.60	%		1.35	%		1.35	%		1.30	%		1.30	%
Emerging Markets Small Cap Growth		1.55	%		1.55	%		1.30	%		1.30	%		1.25	%		1.25	%
Bond		0.60	%		0.60	%		0.45	%		0.45	%		0.40	%		0.40	%
Income		0.85	%		0.85	%		0.70	%		0.70	%		0.65	%		N/A
Low Duration		0.55	%		0.55	%		0.40	%		0.40	%		0.35	%		0.35	%
Macro Allocation		1.25	%		1.25	%		1.00	%		1.00	%		0.95	%		0.95	%

138 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

For the period ended June 30, 2019, the fee waivers and/or expense reimbursements received by each Fund were as follows (in thousands):

Fund	Class N  Waiver		Class I  Waiver		Institutional/Class R6  Waiver		Total  Waiver
Growth		$8		$—		$—		$8
Large Cap Growth		37		75		—		112
Mid Cap Growth		9		100		—		109
Small-Mid Cap Growth		171		616		—		787
Small-Mid Cap Value		13		70		—		83
Small Cap Growth		44		15		—		59
Small Cap Value		6		151		—		157
Global Leaders		7		48		39		94
International Leaders		6		30		72		108
International Developed Plus		3		91		—		94
Institutional International Developed Plus		—		—		56		56
International Growth		41		—		—		41
Institutional International Growth		—		—		—		—
International Small Cap Growth		—		—		—		—
Emerging Markets Leaders		1		11		39		51
Emerging Markets Growth		—		—		—		—
Emerging Markets Small Cap Growth		7		133		70		210
Bond		30		32		—		62
Income		11		1		—		12
Low Duration		2		36		32		70
Macro Allocation		—		—		—		—

(b)Underwriting, Distribution Services, and Shareholder Administration Agreements

Pursuant to separate Underwriting and Distribution Agreements, WBC is the principal underwriter and distributor for the continuous offering of shares of the Trust and acts as agent of the Trust in the sale of its shares. The Underwriting Agreement provides that the Distributor will use its best efforts to distribute the Trust’s shares. The Distributor is not compensated under the Underwriting Agreement.

Each Fund, except the Institutional International Developed Plus Fund and Institutional International Growth Fund, has a Distribution Agreement with WBC for distribution services to the Funds’ Class N shares. Each Fund pays WBC an annual fee, payable monthly, based on a specified percentage of its average daily net assets of Class N shares. The annual rate expressed as a percentage of average daily net assets for Class N is 0.25% for all Funds except the Bond, Income and Low Duration Funds, which is 0.15%. Pursuant to the Distribution Agreement, WBC enters into related selling group agreements with various firms at various rates for sales of the Funds’ Class N shares.

The Global Leaders, International Leaders, International Small Cap Growth, Emerging Markets Leaders, Emerging Markets Growth, Emerging Markets Small Cap Growth, Bond, Low Duration and Macro Allocation Funds have a Shareholder Administration Agreement with WBC to provide shareholder administration services to Class N and Class I shares. Class N and Class I shares of the Funds previously agreed to pay an annual fee, payable monthly, of 0.15% of average daily net assets attributable to each class, respectively, all of which had been waived by WBC since January 2015. Effective January 1, 2018, the fee was reduced to 0.00%. WBC has provided, and continues to provide, shareholder administration services pursuant to the Shareholder Administration Agreements.

June 30, 2019 William Blair Funds 139

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

(5) Investment Transactions

Investment transactions, excluding U.S. government securities and securities whose maturities or expiration dates at the time of purchase were one year or less, for the period ended June 30, 2019, were as follows (in thousands):

Fund	Purchases		Sales
Growth	$	44,023	$	60,904
Large Cap Growth		40,070		32,964
Mid Cap Growth		18,527		20,538
Small-Mid Cap Growth		790,598		904,654
Small-Mid Cap Value		1,008		1,223
Small Cap Growth		201,656		199,305
Small Cap Value		155,163		262,950
Global Leaders		31,760		27,332
International Leaders		108,900		61,159
International Developed Plus		14,481		89,764
Institutional International Developed Plus		5,194		4,833
International Growth		494,386		833,873
Institutional International Growth		400,619		693,761
International Small Cap Growth		59,050		154,059
Emerging Markets Leaders		27,288		38,773
Emerging Markets Growth		311,413		365,103
Emerging Markets Small Cap Growth		247,689		273,933
Bond		116,071		149,913
Income		37,830		33,447
Low Duration		93,828		94,561
Macro Allocation		75,329		174,152

Investment transactions in U.S. government securities whose maturities at the time of purchase were greater than one year for the period ended June 30, 2019, were as follows (in thousands):

Fund	Purchases		Sales
Bond	$	500	$	1,374
Income		—		295
Low Duration		—		—
Macro Allocation		87,878		69,000

140 Semiannual Report June 30, 2019

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

(6) Financial Derivative Instruments

Each Fund may use derivative instruments to maintain liquidity, to provide hedging, or in anticipation of changes in the composition of its portfolio holdings or as otherwise provided in each Fund’s prospectus. Macro Allocation Fund may also use derivative instruments to obtain investment exposures. The derivative instruments held as of June 30, 2019, as disclosed in each Fund’s Portfolios of Investments, are representative of each Fund’s derivative instrument trading activity during the period ended June 30, 2019.

Derivative transactions carry counterparty risk as they are based on contracts between a Fund and the applicable counterparty. For exchange-traded or cleared derivative contracts, such counterparty risk is limited due to the role of the exchange or clearinghouse. OTC derivative contracts, however, are exposed to counterparty risk in the amount of unrealized gains, net of collateral held, for the duration of the contract.

Macro Allocation Fund is subject to certain netting arrangements through International Swaps and Derivatives Association, Inc. Master Agreements and Credit Support Annexes (“ISDAs”). The ISDAs maintain provisions for general obligations, representations, agreements, collateral and events of default or termination. The ISDAs cover certain OTC derivative securities entered into by Macro Allocation Fund with various counterparties and allow Macro Allocation Fund to close out and net its total exposure to a counterparty in the event of a default.

Futures Contracts

A futures contract provides for the future sale by one party and purchase by another party of a specified amount of a specific financial instrument for a specified price at a designated date, time and place. An index futures contract is an agreement pursuant to which the parties agree to take or make delivery of an amount of cash equal to the difference between the value of the index at the close of the last trading day of the contract and the price at which the index futures contract was originally written. A futures contract can be closed out prior to delivery by entering into an offsetting transaction in a matching futures contract. Although the value of an index might be a function of the value of certain specified securities, no physical delivery of those securities is made. If the offsetting purchase price is less than the original sale price, a Fund realizes a gain; if it is more, a Fund realizes a loss. Conversely, if the offsetting sale price is more than the original purchase price, a Fund realizes a gain; if it is less, a Fund realizes a loss. The transaction costs must also be included in these calculations. There can be no assurance, however, that a Fund will be able to enter into an offsetting transaction with respect to a particular futures contract at a particular time. If a Fund is not able to enter into an offsetting transaction, a Fund will continue to be required to maintain the margin deposits on the futures contract.

Upon entering into a futures contract, a Fund is required to pledge to the broker an amount of cash, U.S. government securities, or other liquid assets equal to a certain percentage of the contract amount (“initial margin deposit”). Futures contracts are marked to market daily and an appropriate payable or receivable for the change in value (“variation margin”) is recorded by a Fund and a cash payment is either made to or received from the broker each day. Gains or losses on futures contracts are recognized but not considered realized until the contracts expire or are closed and are included in the Statement of Operations.

Options

The purchase or sale of an option by a Fund involves the payment or receipt of a premium by the investor and the corresponding right or obligation, as the case may be, either to purchase or sell the underlying security, commodity, or other instrument for a specific price at a certain time or during a certain period. Purchasing options involves the risk that the underlying instrument will not change price in the manner expected, so the investor loses its premium. Writing options involves potentially greater risk because the investor is exposed to the extent of the actual price movement in the underlying security rather than only the amount of the premium paid (which could result in a potentially unlimited loss). OTC options also involve counterparty credit risk. Purchased options are shown as an asset in the Statement of Assets and Liabilities and are included in Investments in securities. Premiums received for written options are shown as a liability in the Statement of Assets and Liabilities. Realized gains and losses on the sale, expiration or assignment of an option are disclosed in the Statement of Operations.

Forward Foreign Currency Contracts

The Global Equity, International Equity and Multi-Asset and Alternative Funds may enter into forward foreign currency contracts. When entering into a forward foreign currency contract, a Fund agrees to receive or deliver a fixed quantity of foreign currency for an agreed-upon price on an agreed future date. A Fund’s net equity therein, representing unrealized gain or loss on the contracts as measured by the difference between the forward foreign exchange rates at the dates of entry into the contracts and

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the forward rates at the reporting date, is included in the Statement of Assets and Liabilities as unrealized appreciation/depreciation on forward foreign currency contracts. Realized and unrealized gains and losses are included in the Statement of Operations. These instruments may involve market risk, credit risk, or both kinds of risks in excess of the amount recognized in the Statement of Assets and Liabilities. Risks arise from the possible inability of counterparties to meet the terms of their contracts and from the price movements in currencies.

Swap Contracts

Swap agreements may include total return, interest rate, securities index, commodity, security, currency exchange rate, credit default index, volatility and variance swaps. Cleared swaps are transacted through futures commission merchants that are members of central clearing houses with the clearing house serving as a central counterparty similar to transactions in futures contracts. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. The gross returns to be exchanged or “swapped” between the parties are calculated with respect to a “notional amount” (i.e., the change in the value of a particular dollar amount invested, for example, at a particular interest rate, in a particular foreign currency, or in a “basket” of securities representing a particular index). Swap agreements are subject to the risk that the counterparty to the swap will default on its obligation to pay a Fund and the risk that a Fund will not be able to meet its obligations to pay the counterparty to the swap. Swap agreements may also involve fees, commissions or other costs that may reduce a Fund’s gains from a swap agreement or may cause a Fund to lose money. To the extent permitted by its investment policies and restrictions, a Fund may invest in the following types of swaps:

Credit Default Swaps—A Fund may invest in credit default swaps as a means of “buying” credit protection (i.e., attempting to mitigate the risk of default or credit quality deterioration in some portion of a Fund’s holdings) or “selling” credit protection (i.e., attempting to gain exposure to an underlying issuer’s credit quality characteristics without directly investing in that issuer). A credit default swap is a contract between a buyer and a seller of protection against a pre-defined credit event (e.g., a ratings downgrade or default) on an underlying reference obligation, which may be a single debt instrument or baskets or indices of securities. A Fund may be a buyer or seller of a credit default swap. As a seller of protection on credit default swap agreements, a Fund will generally receive from the buyer of protection a fixed rate of income throughout the term of the swap provided that there is no credit event. A Fund adds leverage to its portfolio because the Fund is subject to investment exposure on the notional amount of the swap. The maximum potential amount of future payments that a Fund as a seller of protection could be required to make under a credit default swap agreement equals the notional amount of the agreement. Notional amounts of each individual credit default swap agreement outstanding as of the period end for which a Fund is the seller of protection are disclosed in the Fund’s Portfolio of Investments. These potential amounts would be partially offset by any recovery values of the respective referenced obligations, upfront payments received upon entering into the agreement, or net amounts received from the settlement of buy protection credit default swap agreements entered into by the same Fund for the same referenced entity or entities. For credit default swap contracts on credit indices, the quoted market prices and resulting values serve as an indicator of the payment performance risk. Increasing market values, in absolute terms when compared to the notional amount of the swap, typically represent deterioration of the referenced entities’ credit soundness and a greater likelihood or risk of default or other credit event occurring as defined under the terms of the swap.

Interest Rate Swap—A Fund may invest in interest rate swaps to gain or mitigate exposure to changes in interest rates. Interest rate swap agreements involve a commitment between parties to pay either a fixed interest rate or a floating interest rate based on a notional amount of principal. The parties make payments at predetermined intervals throughout the life of the swap. As a payer, a Fund would make the fixed payment and receive the floating payment. As a receiver, a Fund would make the floating payment and receive the fixed payment.

Total Return Swap—A Fund may invest in total return swaps to gain or mitigate exposure to an underlying security, or securities. Total return swap agreements may involve commitments to pay interest in exchange for the return on the underlying security, or securities. At maturity, a net cash flow is exchanged between the parties based on the total return of the underlying security, or securities, less a financing rate. As a receiver in the transaction, a Fund would receive a payment for a positive return and would make a payment for a negative return. As a payer in the transaction, a Fund would make a payment for a positive return and would receive a payment for a negative return.

Variance Swap—A Fund may invest in variance swaps in order to gain or mitigate its exposure to an underlying reference entity such as a broad based index. A variance swap is an agreement between two parties to exchange cash flows based on the measured variance of a reference entity. The payer agrees to exchange the fixed rate, which is the variance strike price of the reference

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entity, to the receiver for the floating rate, which is the realized variance price of the reference entity. At the time the trade is originated, the agreed upon variance strike price is generally set so that the fair value of the swap is near zero. At maturity, a net cash flow is exchanged between the parties based on the difference between the final realized variance price of the swap and the variance strike price multiplied by the notional, or vega amount. As a receiver of the floating rate, a Fund would receive a payment if the final realized variance price is greater than the variance strike price and would make a payment if the final realized variance price is less than the variance strike price. As a payer of the floating rate, a Fund would receive a payment if the final realized variance price is less than the variance strike price and would make a payment if the final realized variance price is greater than the variance strike price.

The following table presents the value of financial derivative instruments, by Fund and primary risk exposure, as of June 30, 2019, and their respective location in the Statements of Assets and Liabilities (in thousands):

	Assets			Liabilities
Fund and Primary Risk Exposure	Statements of Assets and Liabilities	Value		Statements of Assets and Liabilities	Value
Bond
Credit	Receivable for variation margin on centrally cleared swaps	$	—	Payable for variation margin on centrally cleared swaps	$	150
Macro Allocation
Credit	Receivable for variation margin on centrally cleared swaps		75	Payable for variation margin on centrally cleared swaps		—
Currency	Unrealized appreciation on forward foreign currency contracts		8,544	Unrealized depreciation on forward foreign currency contracts		10,490
Equity	Receivable for variation margin on futures		3,354	Payable for variation margin on futures		8,311
Equity	Unrealized appreciation on swap contracts		4,063	Unrealized depreciation on swap contracts		—
Interest rate	Unrealized appreciation on swap contracts		919	Unrealized depreciation on swap contracts		1,385
Interest rate	Receivable for variation margin on futures		—	Payable for variation margin on futures		332
Interest rate	Receivable for variation margin on centrally cleared swaps		—	Payable for variation margin on centrally cleared swaps		1,265

The table above includes cumulative appreciation/(depreciation) on futures contracts and centrally cleared swaps as reported in the applicable Fund’s Portfolio of Investments. Variation margin receivable/payable on futures contracts and centrally cleared swaps is reported within the Statements of Assets and Liabilities.

June 30, 2019 William Blair Funds 143

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The following table indicates the effect of derivatives, by Fund and primary risk exposure, in the Statements of Operations for the period ended June 30, 2019 (in thousands):

	Realized Gain (Loss)				Change in Net Unrealized Appreciation (Depreciation)
Fund and Primary Risk Exposure	Statements of Operations	Value			Statements of Operations	Value
Bond
Credit	Swaps	$	(126	)	Swaps	$	(426	)
Macro Allocation
Credit	Swaps		275		Swaps		193
Currency	Forward foreign currency contracts		15,943		Forward foreign currency contracts		(7,141	)
Currency	Options		(1,844	)	Options		1,484
Equity	Futures contracts		(58,877	)	Futures contracts		(13,552	)
Equity	Options		(566	)	Options		(154	)
Equity	Swaps		130		Swaps		4,222
Interest rate	Futures contracts		(1,862	)	Futures contracts		110
Interest rate	Options		(860	)	Options		(409	)
Interest rate	Swaps		(4,161	)	Swaps		(794	)

The following table is a summary by counterparty of the derivative instruments and collateral pledged/(received) included in the Macro Allocation Fund’s Statement of Assets and Liabilities at June 30, 2019 (in thousands):

	Financial Derivative Assets						Financial Derivative Liabilities
Counterparty	Forward Foreign Currency Contracts		Swaps		Total		Forward Foreign Currency Contracts			Swaps			Total			Net Market Value			Collateral Pledged (Received)			Net Exposure
Citibank N.A.	$	8,544	$	2,259	$	10,803	$	(10,490	)	$	—		$	(10,490	)	$	313		$	(313	)	$	—
Credit Suisse		—		919		919		—			(1,385	)		(1,385	)		(466	)		5,925			5,459
Goldman Sachs		—		1,804		1,804		—			—			—			1,804			(1,804	)		—
	$	8,544	$	4,982	$	13,526	$	(10,490	)	$	(1,385	)	$	(11,875	)	$	1,651		$	3,808		$	5,459

The net exposure represents the amount due from the counterparty in the event of default. Any net exposure is generally due to changes in market value of the underlying derivative instruments on the last day of the period as timing of collateral movement occurs the following day. For Credit Suisse, the collateral pledged is due to initial margin requirements of approximately $5,037 (in thousands) for total return swaps on futures contracts and $888 (in thousands) for the net market value of all OTC swaps. The table does not include additional collateral received in the amounts of $1,759 (in thousands) and $46 (in thousands) for Citibank N.A. and Goldman Sachs, respectively.

144 Semiannual Report June 30, 2019

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(7) Fund Share Transactions

The following tables summarize the activity in capital shares of each Fund for the period ended June 30, 2019 (in thousands):

																Class N
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	2,811	$	—	$	8,671	$	(5,860	)		319		—		981		(662	)
Large Cap Growth		13,195		—		8,329		4,866			964		—		609		355
Mid Cap Growth		147		—		436		(289	)		14		—		42		(28	)
Small-Mid Cap Growth		45,480		—		200,334		(154,854	)		1,892		—		8,428		(6,536	)
Small-Mid Cap Value		31		—		68		(37	)		3		—		6		(3	)
Small Cap Growth		34,350		—		38,509		(4,159	)		1,320		—		1,432		(112	)
Small Cap Value		894		—		3,791		(2,897	)		52		—		223		(171	)
Global Leaders		688		—		1,104		(416	)		53		—		86		(33	)
International Leaders		961		—		1,131		(170	)		62		—		72		(10	)
International Developed Plus		31		—		221		(190	)		3		—		15		(12	)
International Growth		35,917		—		75,596		(39,679	)		1,406		—		2,951		(1,545	)
International Small Cap Growth		38		—		559		(521	)		3		—		48		(45	)
Emerging Markets Leaders		2,278		—		2,582		(304	)		242		—		279		(37	)
Emerging Markets Growth		1,321		—		1,683		(362	)		110		—		140		(30	)
Emerging Markets Small Cap Growth		545		—		4,283		(3,738	)		36		—		296		(260	)
Bond		5,599		1,378		13,552		(6,575	)		556		137		1,358		(665	)
Income		903		351		2,926		(1,672	)		107		41		346		(198	)
Low Duration		121		27		187		(39	)		13		3		21		(5	)
Macro Allocation		6,512		—		13,185		(6,673	)		570		—		1,138		(568	)

																Class I
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	8,449	$	—	$	18,438	$	(9,989	)		807		—		1,738		(931	)
Large Cap Growth		19,141		—		16,261		2,880			1,333		—		1,155		178
Mid Cap Growth		3,938		—		6,311		(2,373	)		349		—		556		(207	)
Small-Mid Cap Growth		441,120		—		437,301		3,819			17,129		—		16,854		275
Small-Mid Cap Value		430		—		628		(198	)		40		—		59		(19	)
Small Cap Growth		98,261		—		97,412		849			3,329		—		3,251		78
Small Cap Value		28,829		—		142,163		(113,334	)		1,630		—		8,070		(6,440	)
Global Leaders		5,776		—		4,169		1,607			449		—		316		133
International Leaders		41,606		—		8,949		32,657			2,652		—		588		2,064
International Developed Plus		19		—		87,196		(87,177	)		1		—		5,505		(5,504	)
International Growth		155,129		—		444,231		(289,102	)		5,958		—		16,762		(10,804	)
International Small Cap Growth		27,334		—		63,082		(35,748	)		2,372		—		5,490		(3,118	)
Emerging Markets Leaders		4,307		—		1,799		2,508			459		—		192		267
Emerging Markets Growth		3,912		—		21,106		(17,194	)		314		—		1,680		(1,366	)
Emerging Markets Small Cap Growth		27,540		—		56,237		(28,697	)		1,903		—		3,816		(1,913	)
Bond		29,095		5,037		50,142		(16,010	)		2,944		505		5,071		(1,622	)
Income		14,297		655		8,106		6,846			1,709		78		969		818
Low Duration		4,575		1,036		7,302		(1,691	)		526		119		838		(193	)
Macro Allocation		68,581		—		126,596		(58,015	)		5,954		—		10,953		(4,999	)

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														Institutional/Class R6
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth (a)	$	50	$	—	$	—	$	50			5		—		—		5
Large Cap Growth (a)		52		—		—		52			3		—		—		3
Mid Cap Growth (a)		50		—		—		50			4		—		—		4
Small-Mid Cap Growth (a)		11,346		—		—		11,346			430		—		—		430
Small-Mid Cap Value (a)		18		—		—		8			1		—		—		1
Small Cap Growth (a)		18,416		—		—		18,416			611		—		—		611
Small Cap Value (a)		51		—		—		51			3		—		—		3
Global Leaders		1,469		—		60		1,409			114		—		5		109
International Leaders		25,928		—		11,110		14,818			1,669		—		689		980
Institutional International Developed Plus		2,000		—		1,000		1,000			142		—		70		72
International Growth (a)		51		—		—		51			2		—		—		2
Institutional International Growth		91,490		—		405,198		(313,708	)		6,149		—		27,024		(20,875	)
International Small Cap Growth		3,695		—		58,953		(55,258	)		315		—		4,919		(4,604	)
Emerging Markets Leaders		11,049		—		21,395		(10,346	)		1,218		—		2,324		(1,106	)
Emerging Markets Growth		77,491		—		115,135		(37,644	)		6,344		—		9,265		(2,921	)
Emerging Markets Small Cap Growth		21,646		—		9,017		12,629			1,474		—		612		862
Bond		2,110		1,494		11,402		(7,798	)		214		150		1,149		(785	)
Income (a)		50		—		—		50			6		—		—		6
Low Duration		3,804		501		8,320		(4,015	)		437		57		955		(461	)
Macro Allocation		101,199		—		92,251		8,948			8,782		—		7,962		820

	Net Change in Net Assets Relating to Fund Share Activity
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	11,310	$	—	$	27,109	$	(15,799	)		1,131		—		2,719		(1,588	)
Large Cap Growth		32,388		—		24,590		7,798			2,300		—		1,764		536
Mid Cap Growth		4,135		—		6,747		(2,612	)		367		—		598		(231	)
Small-Mid Cap Growth		497,946		—		637,635		(139,689	)		19,451		—		25,282		(5,831	)
Small-Mid Cap Value		469		—		696		(227	)		44		—		65		(21	)
Small Cap Growth		151,027		—		135,921		15,106			5,260		—		4,683		577
Small Cap Value		29,774		—		145,954		(116,180	)		1,685		—		8,293		(6,608	)
Global Leaders		7,933		—		5,333		2,600			616		—		407		209
International Leaders		68,495		—		21,190		47,305			4,383		—		1,349		3,034
International Developed Plus		50		—		87,417		(87,367	)		4		—		5,520		(5,516	)
Institutional International Developed Plus		2,000		—		1,000		1,000			142		—		70		72
International Growth		191,097		—		519,827		(328,730	)		7,366		—		19,713		(12,347	)
Institutional International Growth		91,490		—		405,198		(313,708	)		6,149		—		27,024		(20,875	)
International Small Cap Growth		31,067		—		122,594		(91,527	)		2,690		—		10,457		(7,767	)
Emerging Markets Leaders		17,634		—		25,776		(8,142	)		1,919		—		2,795		(876	)
Emerging Markets Growth		82,724		—		137,924		(55,200	)		6,768		—		11,085		(4,317	)
Emerging Markets Small Cap Growth		49,731		—		69,537		(19,806	)		3,413		—		4,724		(1,311	)
Bond		36,804		7,909		75,096		(30,383	)		3,714		792		7,578		(3,072	)
Income		15,250		1,006		11,032		5,224			1,822		119		1,315		626
Low Duration		8,500		1,564		15,809		(5,745	)		976		179		1,814		(659	)
Macro Allocation		176,292		—		232,032		(55,740	)		15,306		—		20,053		(4,747	)

(a) For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.

146 Semiannual Report June 30, 2019

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The following tables summarize the activity in capital shares of each Fund for the year ended December 31, 2018 (in thousands):

	Class N
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	23,472	$	11,875	$	21,376	$	13,971			2,069		1,409		2,022		1,456
Large Cap Growth		29,850		6,475		14,335		21,990			2,017		509		994		1,532
Mid Cap Growth		708		913		1,816		(195	)		60		98		165		(7	)
Small-Mid Cap Growth		380,723		37,279		163,129		254,873			15,220		1,679		6,431		10,468
Small-Mid Cap Value		113		58		122		49			7		6		8		5
Small Cap Growth		123,547		23,316		86,965		59,898			4,080		939		3,187		1,832
Small Cap Value		5,677		2,217		14,925		(7,031	)		281		138		782		(363	)
Global Leaders		1,661		1,030		1,425		1,266			109		85		98		96
International Leaders		3,308		312		2,911		709			200		22		181		41
International Developed Plus		210		37		1,229		(982	)		12		3		77		(62	)
International Growth		108,982		38,814		295,580		(147,784	)		3,862		1,621		10,783		(5,300	)
International Small Cap Growth		239		429		1,644		(976	)		17		40		130		(73	)
Emerging Markets Leaders		4,063		179		4,196		46			410		21		410		21
Emerging Markets Growth		1,881		889		2,909		(139	)		116		79		205		(10	)
Emerging Markets Small Cap Growth		3,416		201		6,551		(2,934	)		198		14		377		(165	)
Bond		23,108		3,396		34,380		(7,876	)		2,284		340		3,453		(829	)
Income		2,428		983		19,283		(15,872	)		286		116		2,264		(1,862	)
Low Duration		1,165		56		1,495		(274	)		132		6		169		(31	)
Macro Allocation		22,540		666		19,962		3,244			1,959		59		1,710		308

																	Class I
							Dollars										Shares
Fund	Sales		Reinvest		Redemptions		Total				Sales		Reinvest		Redemptions		Total
Growth	$	19,362	$	48,402	$	178,305	$	(110,541	)			1,521		4,909		13,868		(7,438	)
Large Cap Growth		30,159		17,362		81,956		(34,435	)			1,958		1,293		5,120		(1,869	)
Mid Cap Growth		10,073		8,782		30,355		(11,500	)			806		873		2,485		(806	)
Small-Mid Cap Growth		911,158		156,686		414,703		653,141				34,323		6,690		15,937		25,076
Small-Mid Cap Value		375		381		1,974		(1,218	)			27		39		145		(79	)
Small Cap Growth		202,591		46,926		114,306		135,211				6,183		1,690		3,677		4,196
Small Cap Value		66,163		56,178		145,358		(23,017	)			3,311		3,405		7,213		(497	)
Global Leaders		41,290		12,892		9,995		44,187				2,836		1,066		722		3,180
International Leaders		56,269		2,896		28,827		30,338				3,554		202		1,902		1,854
International Developed Plus		589		2,119		13,397		(10,689	)	��		36		150		843		(657	)
International Growth		200,613		133,989		531,160		(196,558	)			6,692		5,473		18,564		(6,399	)
International Small Cap Growth		82,715		19,411		169,747		(67,621	)			5,533		1,796		13,158		(5,829	)
Emerging Markets Leaders		9,820		3,475		14,210		(915	)			917		412		1,420		(91	)
Emerging Markets Growth		26,970		10,009		49,600		(12,621	)			1,675		876		3,405		(854	)
Emerging Markets Small Cap Growth		101,685		4,171		141,110		(35,254	)			5,901		296		9,187		(2,990	)
Bond		89,791		13,105		182,485		(79,589	)			9,041		1,324		18,497		(8,132	)
Income		8,196		1,300		24,129		(14,633	)			976		154		2,848		(1,718	)
Low Duration		9,060		2,567		84,883		(73,256	)			1,029		291		9,591		(8,271	)
Macro Allocation		204,410		14,124		483,628		(265,094	)			17,377		1,250		41,548		(22,921	)

June 30, 2019 William Blair Funds 147

Notes to Financial Statements(information as of June 30, 2019 is unaudited)

														Institutional/Class R6
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Global Leaders	$	3,889	$	12,002	$	65,440	$	(49,549	)		268		993		4,170		(2,909	)
International Leaders		94,113		12,596		30,591		76,118			5,729		881		1,917		4,693
Institutional International Developed Plus		—		554		50		504			—		45		4		41
Institutional International Growth		268,610		180,253		432,394		16,469			15,659		12,959		24,320		4,298
International Small Cap Growth		12,441		21,099		39,019		(5,479	)		833		1,941		2,717		57
Emerging Markets Leaders		31,986		16,112		231,210		(183,112	)		2,961		1,911		23,818		(18,946	)
Emerging Markets Growth		199,420		70,214		513,600		(243,966	)		14,257		6,095		34,162		(13,810	)
Emerging Markets Small Cap Growth		52,476		2,144		75,303		(20,683	)		2,989		152		5,051		(1,910	)
Bond		4,444		3,613		23,146		(15,089	)		448		366		2,364		(1,550	)
Low Duration		6,065		2,461		58,720		(50,194	)		687		279		6,709		(5,743	)
Macro Allocation		74,626		11,126		161,255		(75,503	)		6,351		985		13,863		(6,527	)

							Net Change in Net Assets Relating to Fund Share Activity
								Dollars									Shares
Fund	Sales		Reinvest		Redemptions			Total			Sales		Reinvest		Redemptions		Total
Growth	$	42,834	$	60,277	$	199,681		$	(96,570	)		3,590		6,318		15,890		(5,982	)
Large Cap Growth		60,009		23,837		96,291			(12,445	)		3,975		1,802		6,114		(337	)
Mid Cap Growth		10,781		9,695		32,171			(11,695	)		866		971		2,650		(813	)
Small-Mid Cap Growth		1,291,881		193,965		577,832			908,014			49,543		8,369		22,368		35,544
Small-Mid Cap Value		488		439		2,096			(1,169	)		34		45		153		(74	)
Small Cap Growth		326,138		70,242		201,271			195,109			10,263		2,629		6,864		6,028
Small Cap Value		71,840		58,395		160,283			(30,048	)		3,592		3,543		7,995		(860	)
Global Leaders		46,840		25,924		76,860			(4,096	)		3,213		2,144		4,990		367
International Leaders		153,690		15,804		62,329			107,165			9,483		1,105		4,000		6,588
International Developed Plus		799		2,156		14,626			(11,671	)		48		153		920		(719	)
Institutional International Developed Plus		—		554	��	50			504			—		45		4		41
International Growth		309,595		172,803		826,740			(344,342	)		10,554		7,094		29,347		(11,699	)
Institutional International Growth		268,610		180,253		432,394			16,469			15,659		12,959		24,320		4,298
International Small Cap Growth		95,395		40,939		210,410			(74,076	)		6,383		3,777		16,005		(5,845	)
Emerging Markets Leaders		45,869		19,766		249,616			(183,981	)		4,288		2,344		25,648		(19,016	)
Emerging Markets Growth		228,271		81,112		566,109			(256,726	)		16,048		7,050		37,772		(14,674	)
Emerging Markets Small Cap Growth		157,577		6,516		222,964			(58,871	)		9,088		462		14,615		(5,065	)
Bond		117,343		20,114		240,011			(102,554	)		11,773		2,030		24,314		(10,511	)
Income		10,624		2,283		43,412			(30,505	)		1,262		270		5,112		(3,580	)
Low Duration		16,290		5,084		145,098			(123,724	)		1,848		576		16,469		(14,045	)
Macro Allocation		301,576		25,916		664,845			(337,353	)		25,687		2,294		57,121		(29,140	)

(8) Subsequent Events

The Funds have evaluated subsequent events through the date of issuance of the Funds’ financial statements and have determined there is no impact to the Funds’ financial statements.

148 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Growth Fund

		Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	7.91		$	10.27		$	11.41		$	12.52		$	13.55		$	14.79
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.04	)		(0.02	)		(0.02	)		(0.04	)		(0.07	)
Net realized and unrealized gain (loss) on investments			1.78			0.75			2.78			(0.08	)		0.75			1.03
Total from investment operations			1.77			0.71			2.76			(0.10	)		0.71			0.96
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			3.07			3.90			1.01			1.74			2.20
Total distributions			—			3.07			3.90			1.01			1.74			2.20
Net asset value, end of year		$	9.68		$	7.91		$	10.27		$	11.41		$	12.52		$	13.55
Total return (%)*			22.38			5.10			24.35			(0.98	)		5.31			6.59
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.24			1.22			1.20			1.21			1.19			1.18
Expenses, net of waivers and reimbursements			1.20			1.20			1.20			1.21			1.19			1.18
Net investment income (loss), before waivers and reimbursements			(0.27	)		(0.36	)		(0.14	)		(0.15	)		(0.29	)		(0.50	)
Net investment income (loss), net of waivers and reimbursements			(0.23	)		(0.34	)		(0.14	)		(0.15	)		(0.29	)		(0.50	)
Class N net assets at the end of the year (in thousands)		$	40,589		$	38,370		$	34,886		$	62,936		$	149,754		$	272,765
Portfolio turnover rate (%)*			18			46			38			79			78			100
		Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	9.25		$	11.51		$	12.39		$	13.50		$	14.43		$	15.56
Income (loss) from investment operations:
Net investment income (loss)			0.00	^		(0.01	)		0.02			0.03			0.01			(0.03	)
Net realized and unrealized gain (loss) on investments			2.09			0.82			3.02			(0.10	)		0.80			1.10
Total from investment operations			2.09			0.81			3.04			(0.07	)		0.81			1.07
Less distributions from:
Net investment income			—			0.00	^		0.02			0.03			—			—
Net realized gain			—			3.07			3.90			1.01			1.74			2.20
Total distributions			—			3.07			3.92			1.04			1.74			2.20
Net asset value, end of year		$	11.34		$	9.25		$	11.51		$	12.39		$	13.50		$	14.43
Total return (%)*			22.59			5.42			24.64			(0.69	)		5.69			6.96
Ratios to average daily net assets (%)**:
Expenses			0.93			0.91			0.92			0.90			0.89			0.86
Net investment income (loss)			0.04			(0.06	)		0.12			0.20			0.06			(0.20	)
Class I net assets at the end of the year (in thousands)		$	219,144		$	187,306		$	318,848		$	514,870		$	696,744		$	688,038
Portfolio turnover rate (%)*			18			46			38			79			78			100

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 149

Financial Highlights— For a share outstanding throughout each period

Growth Fund

		Class R6
	(unaudited)
	Period Ended
	June 30,
			2019(a)
Net asset value, beginning of year		$	11.06
Income (loss) from investment operations:
Net investment income (loss)			0.00	^
Net realized and unrealized gain (loss) on investments			0.28
Total from investment operations			0.28
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	11.34
Total return (%)*			2.53
Ratios to average daily net assets (%)**:
Expenses			0.87
Net investment income (loss)			0.23
Class R6 net assets at the end of the year (in thousands)		$	51
Portfolio turnover rate (%)*			18

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

150 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Large Cap Growth Fund

		Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	11.99		$	13.35		$	10.26		$	10.15		$	10.46		$	10.03
Income (loss) from investment operations:
Net investment income (loss)			0.00	^		(0.02	)		(0.02	)		0.02			(0.02	)		(0.02	)
Net realized and unrealized gain (loss) on investments			2.89			0.81			3.19			0.18			0.75			1.46
Total from investment operations			2.89			0.79			3.17			0.20			0.73			1.44
Less distributions from:
Net investment income			—			—			—			0.01			—			—
Net realized gain			—			2.15			0.08			0.08			1.04			1.01
Total distributions			—			2.15			0.08			0.09			1.04			1.01
Net asset value, end of year		$	14.88		$	11.99		$	13.35		$	10.26		$	10.15		$	10.46
Total return (%)*			24.10			4.96			30.88			1.97			7.04			14.29
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.15			1.21			1.19			1.23			1.28			1.31
Expenses, net of waivers and reimbursements			1.00			1.05			1.05			1.05			1.07			1.13
Net investment income (loss), before waivers and reimbursements			(0.09	)		(0.33	)		(0.27	)		(0.01	)		(0.43	)		(0.41	)
Net investment income (loss), net of waivers and reimbursements			0.06			(0.17	)		(0.13	)		0.17			(0.22	)		(0.23	)
Class N net assets at the end of the year (in thousands)		$	56,605		$	41,361		$	25,604		$	11,860		$	10,443		$	8,831
Portfolio turnover rate (%)*			16			47			29			44			38			50
		Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	12.66		$	13.97		$	10.70		$	10.58		$	10.84		$	10.33
Income (loss) from investment operations:
Net investment income (loss)			0.02			0.01			0.02			0.04			(0.00	)^		0.00	^
Net realized and unrealized gain (loss) on investments			3.05			0.85			3.33			0.19			0.78			1.52
Total from investment operations			3.07			0.86			3.35			0.23			0.78			1.52
Less distributions from:
Net investment income			—			0.02			—			0.03			—			—
Net realized gain			—			2.15			0.08			0.08			1.04			1.01
Total distributions			—			2.17			0.08			0.11			1.04			1.01
Net asset value, end of year		$	15.73		$	12.66		$	13.97		$	10.70		$	10.58		$	10.84
Total return (%)*			24.25			5.21			31.29			2.22			7.26			14.65
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.84			0.90			0.90			0.91			0.95			1.00
Expenses, net of waivers and reimbursements			0.75			0.80			0.80			0.80			0.82			0.88
Net investment income (loss), before waivers and reimbursements			0.22			(0.01	)		0.03			0.30			(0.10	)		(0.10	)
Net investment income (loss), net of waivers and reimbursements			0.31			0.09			0.13			0.41			0.03			0.02
Class I net assets at the end of the year (in thousands)		$	173,745		$	137,599		$	177,959		$	110,475		$	59,038		$	50,778
Portfolio turnover rate (%)*			16			47			29			44			38			50

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 151

Financial Highlights— For a share outstanding throughout each period

Large Cap Growth Fund

		Class R6
	(unaudited)
	Period Ended
	June 30,
	2019(a)
Net asset value, beginning of year		$	15.12
Income (loss) from investment operations:
Net investment income (loss)			0.01
Net realized and unrealized gain (loss) on investments			0.60
Total from investment operations			0.61
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	15.73
Total return (%)*			4.03
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.70
Expenses, net of waivers and reimbursements			0.60
Net investment income (loss), before waivers and reimbursements			0.26
Net investment income (loss), net of waivers and reimbursements			0.36
Class R6 net assets at the end of the year (in thousands)		$	52
Portfolio turnover rate (%)*			16

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

152 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Mid Cap Growth Fund

		Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	8.87		$	10.92		$	10.69		$	11.28		$	14.20		$	15.21
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)		(0.06	)		(0.08	)		(0.06	)		(0.09	)		(0.12	)
Net realized and unrealized gain (loss) on investments			2.45			0.03			2.29			0.09			0.04			1.26
Total from investment operations			2.43			(0.03	)		2.21			0.03			(0.05	)		1.14
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			2.02			1.98			0.62			2.87			2.15
Total distributions			—			2.02			1.98			0.62			2.87			2.15
Net asset value, end of year		$	11.30		$	8.87		$	10.92		$	10.69		$	11.28		$	14.20
Total return (%)*			27.40			(1.20	)		20.88			0.23			(0.20	)		7.53
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.53			1.57			1.49			1.45			1.43			1.35
Expenses, net of waivers and reimbursements			1.20			1.23			1.30			1.30			1.32			1.35
Net investment income (loss), before waivers and reimbursements			(0.78	)		(0.85	)		(0.84	)		(0.68	)		(0.76	)		(0.80	)
Net investment income (loss), net of waivers and reimbursements			(0.45	)		(0.51	)		(0.65	)		(0.53	)		(0.65	)		(0.80	)
Class N net assets at the end of the year (in thousands)		$	5,974		$	4,944		$	6,166		$	16,234		$	25,105		$	37,413
Portfolio turnover rate (%)*			29			58			59			60			65			81
		Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	9.55		$	11.57		$	11.20		$	11.76		$	14.65		$	15.58
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.03	)		(0.05	)		(0.03	)		(0.06	)		(0.09	)
Net realized and unrealized gain (loss) on investments			2.63			0.03			2.40			0.09			0.04			1.31
Total from investment operations			2.62			—			2.35			0.06			(0.02	)		1.22
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			2.02			1.98			0.62			2.87			2.15
Total distributions			—			2.02			1.98			0.62			2.87			2.15
Net asset value, end of year		$	12.17		$	9.55		$	11.57		$	11.20		$	11.76		$	14.65
Total return (%)*			27.43			(0.86	)		21.18			0.48			0.00			7.87
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.29			1.31			1.23			1.18			1.14			1.10
Expenses, net of waivers and reimbursements			0.95			0.98			1.05			1.05			1.07			1.10
Net investment income (loss), before waivers and reimbursements			(0.53	)		(0.58	)		(0.58	)		(0.39	)		(0.48	)		(0.55	)
Net investment income (loss), net of waivers and reimbursements			(0.19	)		(0.25	)		(0.40	)		(0.26	)		(0.41	)		(0.55	)
Class I net assets at the end of the year (in thousands)		$	62,722		$	51,173		$	71,369		$	119,424		$	174,617		$	302,373
Portfolio turnover rate (%)*			29			58			59			60			65			81

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 153

Financial Highlights— For a share outstanding throughout each period

Mid Cap Growth Fund

		Class R6
	(unaudited)
	Period Ended
	June 30,
	2019(a)
Net asset value, beginning of year		$	11.93
Income (loss) from investment operations:
Net investment income (loss)			0.00	^
Net realized and unrealized gain (loss) on investments			0.24
Total from investment operations			0.24
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	12.17
Total return (%)*			2.01
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.14
Expenses, net of waivers and reimbursements			0.90
Net investment income (loss), before waivers and reimbursements.			(0.23	)
Net investment income (loss), net of waivers and reimbursements			0.01
Class R6 net assets at the end of the year (in thousands)		$	51
Portfolio turnover rate (%)*			29

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

154 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Small-Mid Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	20.97		$	23.36		$	19.20		$	18.53		$	18.72		$	18.80
Income (loss) from investment operations:
Net investment income (loss)			(0.09	)		(0.18	)		(0.16	)		(0.09	)		(0.10	)		(0.12	)
Net realized and unrealized gain (loss) on investments			5.18			(0.25	)		5.62			1.29			0.93			1.68
Total from investment operations			5.09			(0.43	)		5.46			1.20			0.83			1.56
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			1.96			1.30			0.53			1.02			1.64
Total distributions			—			1.96			1.30			0.53			1.02			1.64
Net asset value, end of year		$	26.06		$	20.97		$	23.36		$	19.20		$	18.53		$	18.72
Total return (%)*			24.27			(2.29	)		28.57			6.45			4.47			8.33
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.44			1.44			1.43			1.43			1.42			1.38
Expenses, net of waivers and reimbursements			1.35			1.35			1.35			1.35			1.35			1.35
Net investment income (loss), before waivers and reimbursements			(0.86	)		(0.81	)		(0.82	)		(0.59	)		(0.58	)		(0.66	)
Net investment income (loss), net of waivers and reimbursements			(0.77	)		(0.72	)		(0.74	)		(0.51	)		(0.51	)		(0.63	)
Class N net assets at the end of the year (in thousands)		$	357,654		$	424,865		$	228,828		$	171,638		$	169,595		$	83,047
Portfolio turnover rate (%)*			30			46			64			66			44			49
	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	22.12		$	24.48		$	20.02		$	19.25		$	19.36		$	19.34
Income (loss) from investment operations:
Net investment income (loss)			(0.06	)		(0.12	)		(0.11	)		(0.05	)		(0.06	)		(0.08	)
Net realized and unrealized gain (loss) on investments			5.47			(0.28	)		5.87			1.35			0.97			1.74
Total from investment operations			5.41			(0.40	)		5.76			1.30			0.91			1.66
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			1.96			1.30			0.53			1.02			1.64
Total distributions			—			1.96			1.30			0.53			1.02			1.64
Net asset value, end of year		$	27.53		$	22.12		$	24.48		$	20.02		$	19.25		$	19.36
Total return (%)*			24.46			(2.06	)		28.90			6.72			4.74			8.62
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.15			1.16			1.16			1.16			1.15			1.15
Expenses, net of waivers and reimbursements			1.10			1.10			1.10			1.10			1.10			1.10
Net investment income (loss), before waivers and reimbursements			(0.53	)		(0.53	)		(0.55	)		(0.34	)		(0.33	)		(0.43	)
Net investment income (loss), net of waivers and reimbursements			(0.48	)		(0.47	)		(0.49	)		(0.28	)		(0.28	)		(0.38	)
Class I net assets at the end of the year (in thousands)		$	2,469,870		$	1,979,105		$	1,576,180		$	1,090,939		$	1,019,544		$	793,789
Portfolio turnover rate (%)*			30			46			64			66			44			49

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 155

Financial Highlights— For a share outstanding throughout each period

Small-Mid Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,
	2019(a)
Net asset value, beginning of year		$	26.76
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)
Net realized and unrealized gain (loss) on investments			0.79
Total from investment operations			0.78
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	27.54
Total return (%)*			2.91
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.06
Expenses, net of waivers and reimbursements			1.05
Net investment income (loss), before waivers and reimbursements			(0.31	)
Net investment income (loss), net of waivers and reimbursements			(0.30	)
Class R6 net assets at the end of the year (in thousands)		$	11,837
Portfolio turnover rate (%)*			30

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

156 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Small-Mid Cap Value Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	9.31		$	14.31		$	14.53		$	12.54		$	13.63		$	14.11
Income (loss) from investment operations:
Net investment income (loss)			0.05			0.09			0.04			0.04			0.04			0.00	^
Net realized and unrealized gain (loss) on investments			1.49			(2.08	)		1.33			2.55			(0.47	)		0.64
Total from investment operations			1.54			(1.99	)		1.37			2.59			(0.43	)		0.64
Less distributions from:
Net investment income			—			0.03			0.02			0.01			0.01			—
Net realized gain			—			2.98			1.57			0.59			0.65			1.12
Total distributions			—			3.01			1.59			0.60			0.66			1.12
Net asset value, end of year		$	10.85		$	9.31		$	14.31		$	14.53		$	12.54		$	13.63
Total return (%)*			16.67			(15.32	)		9.59			20.69			(3.13	)		4.66
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			10.81			6.88			4.83			4.15			3.93			4.50
Expenses, net of waivers and reimbursements			1.25			1.28			1.35			1.35			1.37			1.40
Net investment income (loss), before waivers and reimbursements			(8.65	)		(4.97	)		(3.21	)		(2.51	)		(2.29	)		(3.08	)
Net investment income (loss), net of waivers and reimbursements			0.91			0.63			0.27			0.29			0.27			0.02
Class N net assets at the end of the year (in thousands)		$	237		$	234		$	284		$	267		$	855		$	946
Portfolio turnover rate (%)*			58			104			70			45			35			69
	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	9.23		$	14.24		$	14.47		$	12.54		$	13.63		$	14.12
Income (loss) from investment operations:
Net investment income (loss)			0.06			0.11			0.07			0.08			0.07			0.05
Net realized and unrealized gain (loss) on investments			1.49			(2.06	)		1.33			2.55			(0.47	)		0.63
Total from investment operations			1.55			(1.95	)		1.40			2.63			(0.40	)		0.68
Less distributions from:
Net investment income			—			0.08			0.06			0.11			0.04			0.05
Net realized gain			—			2.98			1.57			0.59			0.65			1.12
Total distributions			—			3.06			1.63			0.70			0.69			1.17
Net asset value, end of year		$	10.78		$	9.23		$	14.24		$	14.47		$	12.54		$	13.63
Total return (%)*			16.79			(15.03	)		9.84			21.00			(2.86	)		4.96
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			10.39			6.54			4.55			3.92			3.72			4.16
Expenses, net of waivers and reimbursements			1.00			1.03			1.10			1.10			1.12			1.15
Net investment income (loss), before waivers and reimbursements			(8.21	)		(4.69	)		(2.94	)		(2.20	)		(2.08	)		(2.65	)
Net investment income (loss), net of waivers and reimbursements			1.18			0.82			0.51			0.62			0.52			0.36
Class I net assets at the end of the year (in thousands)		$	1,487		$	1,445		$	3,359		$	3,186		$	3,220		$	3,407
Portfolio turnover rate (%)*			58			104			70			45			35			69

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 157

Financial Highlights— For a share outstanding throughout each period

Small-Mid Cap Value Fund

	Class R6
	(unaudited) Period Ended June 30,
	2019(a)
Net asset value, beginning of year		$	10.93
Income (loss) from investment operations:
Net investment income (loss)			0.03
Net realized and unrealized gain (loss) on investments			(0.17	)
Total from investment operations			(0.14	)
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	10.79
Total Return (%)*			(1.28	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			14.63
Expenses, net of waivers and reimbursements			0.95
Net investment income (loss), before waivers and reimbursements			(12.04	)
Net investment income (loss), net of waivers and reimbursements			1.64
Class R6 net assets at the end of the year (in thousands)		$	10
Portfolio turnover rate (%)*			58

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

158 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Small Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	23.23		$	26.87		$	25.24		$	22.47		$	25.61		$	30.02
Income (loss) from investment operations:
Net investment income (loss)			(0.12	)		(0.27	)		(0.25	)		(0.18	)		(0.22	)		(0.30	)
Net realized and unrealized gain (loss) on investments			4.53			(0.10	)		6.88			4.43			(0.93	)		1.02
Total from investment operations			4.41			(0.37	)		6.63			4.25			(1.15	)		0.72
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			3.27			5.00			1.48			1.99			5.13
Total distributions			—			3.27			5.00			1.48			1.99			5.13
Net asset value, end of year		$	27.64		$	23.23		$	26.87		$	25.24		$	22.47		$	25.61
Total return (%)*			18.98			(2.14	)		26.70			18.89			(4.44	)		2.62
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.54			1.55			1.54			1.55			1.59			1.56
Expenses, net of waivers and reimbursements			1.50			1.50			1.50			1.50			1.50			1.50
Net investment income (loss), before waivers and reimbursements			(0.93	)		(0.94	)		(0.93	)		(0.84	)		(0.94	)		(1.06	)
Net investment income (loss), net of waivers and reimbursements			(0.89	)		(0.89	)		(0.89	)		(0.79	)		(0.85	)		(1.00	)
Class N net assets at the end of the year (in thousands)		$	198,064		$	169,074		$	146,291		$	117,068		$	111,944		$	148,201
Portfolio turnover rate (%)*			29			74			81			90			91			82
	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	25.99		$	29.61		$	27.34		$	24.17		$	27.32		$	31.61
Income (loss) from investment operations:
Net investment income (loss)			(0.10	)		(0.21	)		(0.20	)		(0.13	)		(0.17	)		(0.23	)
Net realized and unrealized gain (loss) on investments			5.07			(0.14	)		7.47			4.78			(0.99	)		1.07
Total from investment operations			4.97			(0.35	)		7.27			4.65			(1.16	)		0.84
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			3.27			5.00			1.48			1.99			5.13
Total distributions			—			3.27			5.00			1.48			1.99			5.13
Net asset value, end of year		$	30.96		$	25.99		$	29.61		$	27.34		$	24.17		$	27.32
Total return (%)*			19.12			(1.88	)		26.99			19.22			(4.20	)		2.87
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.26			1.25			1.25			1.27			1.30			1.30
Expenses, net of waivers and reimbursements			1.25			1.25			1.25			1.25			1.25			1.25
Net investment income (loss), before waivers and reimbursements			(0.65	)		(0.65	)		(0.64	)		(0.56	)		(0.66	)		(0.80	)
Net investment income (loss), net of waivers and reimbursements			(0.64	)		(0.65	)		(0.64	)		(0.54	)		(0.61	)		(0.75	)
Class I net assets at the end of the year (in thousands)		$	491,045		$	410,233		$	343,119		$	271,830		$	261,269		$	364,241
Portfolio turnover rate (%)*			29			74			81			90			91			82

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 159

Financial Highlights— For a share outstanding throughout each period

Small Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,
	2019(a)
Net asset value, beginning of year		$	31.00
Income (loss) from investment operations:
Net investment income (loss)			0.03
Net realized and unrealized gain (loss) on investments			(0.07	)
Total from investment operations			(0.04	)
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	30.96
Total Return (%)*			(0.13	)
Ratios to average daily net assets (%)**:
Expenses			1.17
Net investment income (loss)			0.49
Class R6 net assets at the end of the year (in thousands)		$	18,923
Portfolio turnover rate (%)*			29

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

160 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Small Cap Value Fund

				Class N
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	15.04	$	20.15		$	20.18		$	16.68	$	17.76		$	17.63
Income (loss) from investment operations:
Net investment income (loss)			0.04		0.03			0.01			0.04		0.02			(0.03	)
Net realized and unrealized gain (loss) on investments			2.40		(3.12	)		1.50			4.34		(1.05	)		0.81
Total from investment operations			2.44		(3.09	)		1.51			4.38		(1.03	)		0.78
Less distributions from:
Net investment income			—		—			—			0.04		—			—
Net realized gain			—		2.02			1.54			0.84		0.05			0.65
Total distributions			—		2.02			1.54			0.88		0.05			0.65
Net asset value, end of year		$	17.48	$	15.04		$	20.15		$	20.18	$	16.68		$	17.76
Total return (%)*			16.22		(15.93	)		7.57			26.19		(5.77	)		4.49
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.57		1.56			1.55			1.53		1.54			1.53
Expenses, net of waivers and reimbursements			1.50		1.50			1.50			1.50		1.50			1.50
Net investment income (loss), before waivers and reimbursements			0.37		0.08			(0.01	)		0.19		0.10			(0.20	)
Net investment income (loss), net of waivers and reimbursements			0.44		0.14			0.04			0.22		0.14			(0.17	)
Class N net assets at the end of the year (in thousands)		$	16,055	$	16,381		$	29,271		$	33,359	$	33,351		$	40,223
Portfolio turnover rate (%)*			32		56			38			33		30			39
					Class I
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019			2018		2017			2016		2015			2014
Net asset value, beginning of year		$	15.50	$	20.70		$	20.68		$	17.08	$	18.17		$	18.00
Income (loss) from investment operations:
Net investment income (loss)			0.06		0.08			0.06			0.09		0.08			0.02
Net realized and unrealized gain (loss) on investments			2.48		(3.21	)		1.54			4.44		(1.08	)		0.82
Total from investment operations			2.54		(3.13	)		1.60			4.53		(1.00	)		0.84
Less distributions from:
Net investment income			—		0.05			0.04			0.09		0.04			0.02
Net realized gain			—		2.02			1.54			0.84		0.05			0.65
Total distributions			—		2.07			1.58			0.93		0.09			0.67
Net asset value, end of year		$	18.04	$	15.50		$	20.70		$	20.68	$	17.08		$	18.17
Total return (%)*			16.39		(15.74	)		7.85			26.46		(5.47	)		4.73
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.31		1.30			1.29			1.29		1.24			1.23
Expenses, net of waivers and reimbursements			1.25		1.25			1.25			1.25		1.24			1.23
Net investment income (loss), before waivers and reimbursements			0.64		0.36			0.25			0.43		0.43			0.12
Net investment income (loss), net of waivers and reimbursements			0.70		0.41			0.29			0.47		0.43			0.12
Class I net assets at the end of the year (in thousands)		$	436,832	$	475,134		$	644,749		$	675,272	$	579,010		$	544,963
Portfolio turnover rate (%)*			32		56			38			33		30			39

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 161

Financial Highlights— For a share outstanding throughout each period

Small Cap Value Fund

	Class R6
	(unaudited)
	Period Ended
	June 30,
	2019(a)
Net asset value, beginning of year		$	18.19
Income (loss) from investment operations:
Net investment income (loss)			0.04
Net realized and unrealized gain (loss) on investments			(0.18	)
Total from investment operations			(0.14	)
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	18.05
Total Return (%)*			(0.77	)
Ratios to average daily net assets (%)**:
Expenses			1.17
Net investment income (loss)			1.30
Class R6 net assets at the end of the year (in thousands)		$	50
Portfolio turnover rate (%)*			32

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

162 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Global Leaders Fund

				Class N
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	11.47	$	14.53		$	11.60	$	11.58		$	11.84		$	11.43
Income (loss) from investment operations:
Net investment income (loss)			0.03		0.02			0.05		0.03			0.02			0.02
Net realized and unrealized gain (loss) on investments			2.34		(1.12	)		3.46		0.04			0.27			0.41
Total from investment operations			2.37		(1.10	)		3.51		0.07			0.29			0.43
Less distributions from:
Net investment income			—		—			0.10		—			0.01			—
Net realized gain			—		1.96			0.48		0.05			0.54			0.02
Total distributions			—		1.96			0.58		0.05			0.55			0.02
Net asset value, end of year		$	13.84	$	11.47		$	14.53	$	11.60		$	11.58		$	11.84
Total return (%)*			20.66		(8.23	)		30.31		0.62			2.49			3.76
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.42		1.47			1.63		1.62			1.61			1.62
Expenses, net of waivers and reimbursements			1.25		1.33			1.37		1.36			1.39			1.50
Net investment income (loss), before waivers and reimbursements			0.29		(0.01	)		0.09		(0.03	)		(0.10	)		0.04
Net investment income (loss), net of waivers and reimbursements			0.46		0.13			0.35		0.23			0.12			0.16
Class N net assets at the end of the year (in thousands)		$	8,263	$	7,225		$	7,761	$	5,760		$	5,588		$	5,007
Portfolio turnover rate (%)*			14		49			41		75			55			60
				Class I
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	11.47	$	14.56		$	11.62	$	11.59		$	11.85		$	11.42
Income (loss) from investment operations:
Net investment income (loss)			0.05		0.06			0.09		0.06			0.06			0.04
Net realized and unrealized gain (loss) on investments			2.35		(1.13	)		3.47		0.05			0.26			0.43
Total from investment operations			2.40		(1.07	)		3.56		0.11			0.32			0.47
Less distributions from:
Net investment income			—		0.06			0.14		0.03			0.04			0.02
Net realized gain			—		1.96			0.48		0.05			0.54			0.02
Total distributions			—		2.02			0.62		0.08			0.58			0.04
Net asset value, end of year		$	13.87	$	11.47		$	14.56	$	11.62		$	11.59		$	11.85
Total return (%)*			20.92		(8.06	)		30.69		0.98			2.77			4.08
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.10		1.15			1.33		1.31			1.32			1.33
Expenses, net of waivers and reimbursements			1.00		1.07			1.07		1.05			1.10			1.25
Net investment income (loss), before waivers and reimbursements			0.61		0.31			0.39		0.28			0.23			0.30
Net investment income (loss), net of waivers and reimbursements			0.71		0.39			0.65		0.54			0.45			0.38
Class I net assets at the end of the year (in thousands)		$	103,148	$	83,790		$	60,067	$	45,772		$	45,853		$	52,090
Portfolio turnover rate (%)*			14		49			41		75			55			60

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 163

Financial Highlights— For a share outstanding throughout each period

Global Leaders Fund

				Class R6
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015		2014
Net asset value, beginning of year		$	11.47	$	14.56		$	11.62	$	11.59	$	11.85	$	11.42
Income (loss) from investment operations:
Net investment income (loss)			0.05		0.07			0.10		0.07		0.06		0.06
Net realized and unrealized gain (loss) on investments			2.35		(1.13	)		3.47		0.05		0.27		0.43
Total from investment operations			2.40		(1.06	)		3.57		0.12		0.33		0.49
Less distributions from:
Net investment income			—		0.07			0.15		0.04		0.05		0.04
Net realized gain			—		1.96			0.48		0.05		0.54		0.02
Total distributions			—		2.03			0.63		0.09		0.59		0.06
Net asset value, end of year		$	13.87	$	11.47		$	14.56	$	11.62	$	11.59	$	11.85
Total return (%)*			20.92		(7.99	)		30.78		1.03		2.85		4.24
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.03		1.08			1.10		1.11		1.11		1.13
Expenses, net of waivers and reimbursements			0.95		1.00			1.00		1.00		1.03		1.10
Net investment income (loss), before waivers and reimbursements			0.68		0.39			0.65		0.48		0.39		0.48
Net investment income (loss), net of waivers and reimbursements			0.76		0.47			0.75		0.59		0.47		0.51
Class R6 net assets at the end of the year (in thousands)		$	97,875	$	79,685		$	143,521	$	125,199	$	137,527	$	106,565
Portfolio turnover rate (%)*			14		49			41		75		55		60

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

164 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

International Leaders Fund

				Class N
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	13.80	$	16.37		$	12.88	$	12.89		$	12.25	$	12.65
Income (loss) from investment operations:
Net investment income (loss)			0.10		0.13			0.11		0.03			0.07		0.13
Net realized and unrealized gain (loss) on investments			2.74		(2.19	)		3.70		0.08			0.66		(0.47	)
Total from investment operations			2.84		(2.06	)		3.81		0.11			0.73		(0.34	)
Less distributions from:
Net investment income			—		0.06			0.20		0.12			0.02		0.06
Net realized gain			—		0.45			0.12		—			0.07		—
Total distributions			—		0.51			0.32		0.12			0.09		0.06
Net asset value, end of year		$	16.64	$	13.80		$	16.37	$	12.88		$	12.89	$	12.25
Total return (%)*			20.58		(12.70	)		29.65		0.88			6.01		(2.67	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.34		1.39			1.59		1.56			1.56		1.59
Expenses, net of waivers and reimbursements			1.22		1.28			1.35		1.30			1.24		1.45
Net investment income (loss), before waivers and reimbursements			1.16		0.70			0.48		(0.02	)		0.19		0.86
Net investment income (loss), net of waivers and reimbursements			1.28		0.81			0.72		0.24			0.51		1.00
Class N net assets at the end of the year (in thousands)		$	10,341	$	8,715		$	9,651	$	2,922		$	377	$	150
Portfolio turnover rate (%)*			13		33			41		59			29		79
				Class I
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
			2019	2018			2017		2016			2015		2014
Net asset value, beginning of year		$	13.84	$	16.44		$	12.92	$	12.91		$	12.25	$	12.65
Income (loss) from investment operations:
Net investment income (loss)			0.13		0.17			0.16		0.10			0.10		0.16
Net realized and unrealized gain (loss) on investments			2.73		(2.19	)		3.71		0.04			0.65		(0.47	)
Total from investment operations			2.86		(2.02	)		3.87		0.14			0.75		(0.31	)
Less distributions from:
Net investment income			—		0.13			0.23		0.13			0.02		0.09
Net realized gain			—		0.45			0.12		—			0.07		—
Total distributions			—		0.58			0.35		0.13			0.09		0.09
Net asset value, end of year		$	16.70	$	13.84		$	16.44	$	12.92		$	12.91	$	12.25
Total return (%)*			20.66		(12.45	)		30.05		1.10			6.18		(2.43	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.02		1.07			1.28		1.30			1.46		1.29
Expenses, net of waivers and reimbursements			0.96		1.03			1.05		1.04			1.13		1.20
Net investment income (loss), before waivers and reimbursements			1.55		1.02			0.86		0.48			0.42		1.16
Net investment income (loss), net of waivers and reimbursements			1.61		1.06			1.09		0.74			0.75		1.25
Class I net assets at the end of the year (in thousands)		$	126,671	$	76,382		$	60,279	$	30,944		$	13,474	$	9,561
Portfolio turnover rate (%)*			13		33			41		59			29		79

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 165

Financial Highlights— For a share outstanding throughout each period

International Leaders Fund

				Class R6
	(unaudited)
	Period Ended
	June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015		2014
Net asset value, beginning of year		$	13.83	$	16.43		$	12.92	$	12.90	$	12.24	$	12.65
Income (loss) from investment operations:
Net investment income (loss)			0.12		0.18			0.18		0.12		0.11		0.17
Net realized and unrealized gain (loss) on investments			2.75		(2.19	)		3.70		0.04		0.66		(0.47	)
Total from investment operations			2.87		(2.01	)		3.88		0.16		0.77		(0.30	)
Less distributions from:
Net investment income			—		0.14			0.25		0.14		0.04		0.11
Net realized gain			—		0.45			0.12		—		0.07		—
Total distributions			—		0.59			0.37		0.14		0.11		0.11
Net asset value, end of year		$	16.70	$	13.83		$	16.43	$	12.92	$	12.90	$	12.24
Total return (%)*			20.75		(12.38	)		30.08		1.25		6.33		(2.34	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.95		0.99			1.03		1.06		1.15		1.14
Expenses, net of waivers and reimbursements			0.91		0.95			0.95		0.95		0.98		1.05
Net investment income (loss), before waivers and reimbursements			1.55		1.07			1.10		0.81		0.71		1.24
Net investment income (loss), net of waivers and reimbursements			1.59		1.11			1.18		0.92		0.88		1.33
Class R6 net assets at the end of the year (in thousands)		$	408,608	$	324,902		$	308,898	$	221,356	$	102,227	$	78,251
Portfolio turnover rate (%)*			13		33			41		59		29		79

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

166 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

International Developed Plus Fund (In Liquidation)

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	13.56	$	16.60		$	13.68	$	13.85		$	13.76	$	14.28
Income (loss) from investment operations:
Net investment income (loss)		��	0.09		0.17			0.12		0.18			0.15		0.16
Net realized and unrealized gain (loss) on investments			2.76		(2.93	)		3.08		(0.22	)		0.06		(0.60	)
Total from investment operations			2.85		(2.76	)		3.20		(0.04	)		0.21		(0.44	)
Less distributions from:
Net investment income			—		0.17			0.28		0.13			0.12		0.08
Net realized gain			—		0.11			—		—			—		—
Total distributions			—		0.28			0.28		0.13			0.12		0.08
Net asset value, end of year		$	16.41	$	13.56		$	16.60	$	13.68		$	13.85	$	13.76
Total return (%)*			21.02		(16.68	)		23.43		(0.27	)		1.54		(3.09	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.51		1.48			1.54		1.60			1.60		1.56
Expenses, net of waivers and reimbursements			1.25		1.27			1.30		1.30			1.32		1.38
Net investment income (loss), before waivers and reimbursements			0.94		0.83			0.54		1.00			0.73		0.93
Net investment income (loss), net of waivers and reimbursements			1.20		1.04			0.78		1.30			1.01		1.11
Class N net assets at the end of the year (in thousands)		$	1,963	$	1,794		$	3,219	$	2,954		$	3,020	$	3,497
Portfolio turnover rate (%)*			23		65			80		70			54		73
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	13.66	$	16.76		$	13.81	$	13.98		$	13.91	$	14.43
Income (loss) from investment operations:
Net investment income (loss)			0.09		0.19			0.15		0.21			0.18		0.19
Net realized and unrealized gain (loss) on investments			2.80		(2.94	)		3.12		(0.22	)		0.07		(0.59	)
Total from investment operations			2.89		(2.75	)		3.27		(0.01	)		0.25		(0.40	)
Less distributions from:
Net investment income			—		0.24			0.32		0.16			0.18		0.12
Net realized gain			—		0.11			—		—			—		—
Total distributions			—		0.35			0.32		0.16			0.18		0.12
Net asset value, end of year		$	16.55	$	13.66		$	16.76	$	13.81		$	13.98	$	13.91
Total return (%)*			21.16		(16.47	)		23.72		(0.02	)		1.80		(2.80	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.28		1.22			1.26		1.34			1.34		1.32
Expenses, net of waivers and reimbursements			1.00		1.02			1.05		1.05			1.07		1.13
Net investment income (loss), before waivers and reimbursements			0.97		0.96			0.72		1.23			0.99		1.16
Net investment income (loss), net of waivers and reimbursements			1.25		1.16			0.93		1.52			1.26		1.35
Class I net assets at the end of the year (in thousands)		$	14,048	$	86,787		$	117,520	$	84,383		$	60,886	$	65,012
Portfolio turnover rate (%)*			23		65			80		70			54		73

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 167

Financial Highlights— For a share outstanding throughout each period

Institutional International Developed Plus Fund (In Liquidation)

	Institutional
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	11.94	$	14.55		$	11.84	$	12.12		$	12.01	$	12.70
Income (loss) from investment operations:
Net investment income (loss)			0.10		0.18			0.16		0.20			0.15		0.21
Net realized and unrealized gain (loss) on investments			2.37		(2.37	)		2.71		(0.24	)		0.08		(0.65	)
Total from investment operations			2.47		(2.19	)		2.87		(0.04	)		0.23		(0.44	)
Less distributions from:
Net investment income			—		0.42			0.16		0.24			0.12		0.25
Net realized gain			—		—			—		—			—		—
Total distributions			—		0.42			0.16		0.24			0.12		0.25
Net asset value, end of year		$	14.41	$	11.94		$	14.55	$	11.84		$	12.12	$	12.01
Total return (%)*			20.69		(15.12	)		24.28		(0.27	)		1.91		(3.50	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.50		1.62			1.68		1.77			1.76		1.63
Expenses, net of waivers and reimbursements			0.90		0.90			0.93		1.00			1.00		1.03
Net investment income (loss), before waivers and reimbursements			0.96		0.53			0.41		0.92			0.47		1.01
Net investment income (loss), net of waivers and reimbursements			1.56		1.25			1.16		1.69			1.23		1.61
Net assets at the end of the year (in thousands)		$	20,529	$	16,155		$	19,090	$	16,565		$	16,030	$	14,574
Portfolio turnover rate (%)*			27		68			73		75			54		61

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

168 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

International Growth Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	23.04	$	30.41		$	23.86	$	24.94		$	25.24		$	26.30
Income (loss) from investment operations:
Net investment income (loss)			0.15		0.16			0.21		0.20			0.18			0.31
Net realized and unrealized gain (loss) on investments			4.29		(5.56	)		6.73		(0.92	)		(0.25	)		(1.15	)
Total from investment operations			4.44		(5.40	)		6.94		(0.72	)		(0.07	)		(0.84	)
Less distributions from:
Net investment income			—		0.12			0.39		0.36			0.23			0.22
Net realized gain			—		1.85			—		—			—			—
Total distributions			—		1.97			0.39		0.36			0.23			0.22
Net asset value, end of year		$	27.48	$	23.04		$	30.41	$	23.86		$	24.94		$	25.24
Total return (%)*			19.27		(18.00	)		29.11		(2.88	)		(0.27	)		(3.19	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.47		1.46			1.47		1.43			1.42			1.44
Expenses, net of waivers and reimbursements			1.45		1.45			1.45		1.43			1.42			1.44
Net investment income (loss), before waivers and reimbursements			1.17		0.54			0.76		0.84			0.71			1.17
Net investment income (loss), net of waivers and reimbursements			1.19		0.55			0.78		0.84			0.71			1.17
Class N net assets at the end of the year (in thousands)		$	502,011	$	456,533		$	763,740	$	729,544		$	1,023,588		$	978,433
Portfolio turnover rate (%)*			23		78			82		101			70			79
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	23.56	$	31.13		$	24.42	$	25.51		$	25.82		$	26.91
Income (loss) from investment operations:
Net investment income (loss)			0.19		0.26			0.30		0.29			0.27			0.36
Net realized and unrealized gain (loss) on investments			4.39		(5.70	)		6.89		(0.94	)		(0.28	)		(1.13	)
Total from investment operations			4.58		(5.44	)		7.19		(0.65	)		(0.01	)		(0.77	)
Less distributions from:
Net investment income			—		0.28			0.48		0.44			0.30			0.32
Net realized gain			—		1.85			—		—			—			—
Total distributions			—		2.13			0.48		0.44			0.30			0.32
Net asset value, end of year		$	28.14	$	23.56		$	31.13	$	24.42		$	25.51		$	25.82
Total return (%)*			19.44		(17.73	)		29.49		(2.54	)		(0.03	)		(2.86	)
Ratios to average daily net assets (%)**:
Expenses			1.15		1.13			1.14		1.13			1.14			1.14
Net investment income (loss)			1.44		0.86			1.08		1.16			1.02			1.36
Class I net assets at the end of the year (in thousands)		$	1,662,854	$	1,646,811		$	2,375,326	$	2,251,701		$	2,655,156		$	2,705,054
Portfolio turnover rate (%)*			23		78			82		101			70			79

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 169

Financial Highlights— For a share outstanding throughout each period

International Growth Fund

	Class R6
	(unaudited) Period Ended June 30,
	2019(a)
Net asset value, beginning of year		$	27.56
Income (loss) from investment operations:
Net investment income (loss)			0.11
Net realized and unrealized gain (loss) on investments			0.47
Total from investment operations			0.58
Less distributions from:
Net investment income			—
Net realized gain			—
Total distributions			—
Net asset value, end of year		$	28.14
Total Return (%)*			2.10
Ratios to average daily net assets (%)**:
Expenses			1.08
Net investment income (loss)			2.30
Class R6 net assets at end of year (in thousands)		$	51
Portfolio turnover rate (%)*			23

(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

170 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Institutional International Growth Fund

	Institutional
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	13.40	$	18.08		$	14.55	$	15.08		$	15.26		$	17.40
Income (loss) from investment operations:
Net investment income (loss)			0.12		0.18			0.21		0.18			0.19			0.26
Net realized and unrealized gain (loss) on investments			2.48		(3.29	)		4.07		(0.54	)		(0.18	)		(0.71	)
Total from investment operations			2.60		(3.11	)		4.28		(0.36	)		0.01			(0.45	)
Less distributions from:
Net investment income			—		0.17			0.44		0.17			0.09			0.32
Net realized gain			—		1.40			0.31		—			0.10			1.37
Total distributions			—		1.57			0.75		0.17			0.19			1.69
Net asset value, end of year		$	16.00	$	13.40		$	18.08	$	14.55		$	15.08		$	15.26
Total return (%)*			19.40		(17.50	)		29.53		(2.40	)		0.09			(2.66	)
Ratios to average daily net assets (%)**:
Expenses			0.99		0.97			0.97		0.98			0.96			0.97
Net investment income (loss),			1.62		1.01			1.22		1.25			1.18			1.50
Net assets at the end of the year (in thousands)		$	1,797,317	$	1,784,435		$	2,330,299	$	2,093,971		$	2,335,632		$	2,339,169
Portfolio turnover rate (%)*			22		82			84		105			70			83

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 171

Financial Highlights— For a share outstanding throughout each period

International Small Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	10.36	$	15.49		$	12.87	$	13.50		$	12.56	$	16.08
Income (loss) from investment operations:
Net investment income (loss)			0.07		0.04			0.12		0.10			0.05		0.03
Net realized and unrealized gain (loss) on investments			1.87		(3.78	)		3.98		(0.72	)		1.16		(1.38	)
Total from investment operations			1.94		(3.74	)		4.10		(0.62	)		1.21		(1.35	)
Less distributions from:
Net investment income			—		0.08			0.32		0.01			0.24		0.18
Net realized gain			—		1.31			1.16		0.00	^		0.03		1.99
Total distributions			—		1.39			1.48		0.01			0.27		2.17
Net asset value, end of year		$	12.30	$	10.36		$	15.49	$	12.87		$	13.50	$	12.56
Total return (%)*			18.73		(24.48	)		32.17		(4.60	)		9.67		(8.43	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.50		1.48			1.62		1.59			1.62		1.58
Expenses, net of waivers and reimbursements			1.50		1.48			1.47		1.44			1.47		1.58
Net investment income (loss), before waivers and reimbursements			1.15		0.29			0.70		0.62			0.19		0.20
Net investment income (loss), net of waivers and reimbursements			1.15		0.29			0.85		0.77			0.34		0.20
Class N net assets at the end of the year (in thousands)		$	3,534	$	3,440		$	6,275	$	10,361		$	11,350	$	13,676
Portfolio turnover rate (%)*			18		88			64		73			90		127
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	10.45	$	15.65		$	13.00	$	13.65		$	12.70	$	16.23
Income (loss) from investment operations:
Net investment income (loss)			0.08		0.09			0.14		0.14			0.09		0.09
Net realized and unrealized gain (loss) on investments			1.90		(3.84	)		4.07		(0.75	)		1.18		(1.40	)
Total from investment operations			1.98		(3.75	)		4.21		(0.61	)		1.27		(1.31	)
Less distributions from:
Net investment income			—		0.14			0.40		0.04			0.29		0.23
Net realized gain			—		1.31			1.16		0.00^			0.03		1.99
Total distributions			—		1.45			1.56		0.04			0.32		2.22
Net asset value, end of year		$	12.43	$	10.45		$	15.65	$	13.00		$	13.65	$	12.70
Total return (%)*			18.95		(24.29	)		32.70		(4.41	)		10.00		(8.10	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.24		1.18			1.31		1.30			1.31		1.28
Expenses, net of waivers and reimbursements			1.24		1.18			1.16		1.15			1.16		1.28
Net investment income (loss), before waivers and reimbursements			1.38		0.60			0.77		0.91			0.51		0.56
Net investment income (loss), net of waivers and reimbursements			1.38		0.60			0.92		1.06			0.66		0.56
Class I net assets at the end of the year (in thousands)		$	158,003	$	165,451		$	338,920	$	306,526		$	342,232	$	364,161
Portfolio turnover rate (%)*			18		88			64		73			90		127

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

172 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

International Small Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015		2014
Net asset value, beginning of year		$	10.50	$	15.73		$	13.07	$	13.72		$	12.77	$	16.32
Income (loss) from investment operations:
Net investment income (loss)			0.09		0.10			0.15		0.15			0.10		0.12
Net realized and unrealized gain (loss) on investments			1.90		(3.85	)		4.08		(0.74	)		1.18		(1.41	)
Total from investment operations			1.99		(3.75	)		4.23		(0.59	)		1.28		(1.29	)
Less distributions from:
Net investment income			—		0.17			0.41		0.06			0.30		0.27
Net realized gain			—		1.31			1.16		0.00	^		0.03		1.99
Total distributions			—		1.48			1.57		0.06			0.33		2.26
Net asset value, end of year		$	12.49	$	10.50		$	15.73	$	13.07		$	13.72	$	12.77
Total return (%)*			18.95		(24.19	)		32.70		(4.31	)		10.03		(7.91	)
Ratios to average daily net assets (%)**:
Expenses			1.13		1.08			1.08		1.07			1.08		1.06
Net investment income (loss)			1.52		0.67			0.99		1.13			0.76		0.74
Class R6 net assets at the end of the year (in thousands)		$	146,917	$	171,833		$	256,558	$	199,746		$	221,018	$	245,103
Portfolio turnover rate (%)*			18		88			64		73			90		127

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 173

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Leaders Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.26	$	11.06		$	7.84		$	7.73	$	9.06		$	9.10
Income (loss) from investment operations:
Net investment income (loss)			0.03		0.03			0.01			0.02		0.02			0.05
Net realized and unrealized gain (loss) on investments			1.35		(1.97	)		3.26			0.09		(1.34	)		0.14
Total from investment operations			1.38		(1.94	)		3.27			0.11		(1.32	)		0.19
Less distributions from:
Net investment income			—		0.07			0.05			—		—			0.00	^
Net realized gain			—		0.79			—			—		0.01			0.23
Total distributions			—		0.86			0.05			—		0.01			0.23
Net asset value, end of year		$	9.64	$	8.26		$	11.06		$	7.84	$	7.73		$	9.06
Total return (%)*			16.71		(17.73	)		41.68			1.42		(14.56	)		2.17
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.62		1.60			1.62			1.81		1.89			1.82
Expenses, net of waivers and reimbursements			1.50		1.58			1.47			1.57		1.64			1.65
Net investment income (loss), before waivers and reimbursements			0.61		0.27			(0.01	)		0.05		(0.07	)		0.34
Net investment income (loss), net of waivers and reimbursements			0.73		0.29			0.14			0.29		0.18			0.51
Class N net assets at the end of the year (in thousands)		$	2,260	$	2,239		$	2,766		$	2,479	$	1,599		$	1,832
Portfolio turnover rate (%)*			13		52			59			135		110			131
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.27	$	11.09		$	7.87		$	7.74	$	9.08		$	9.10
Income (loss) from investment operations:
Net investment income (loss)			0.05		0.06			0.02			0.04		0.05			0.08
Net realized and unrealized gain (loss) on investments			1.35		(1.97	)		3.27			0.10		(1.36	)		0.15
Total from investment operations			1.40		(1.91	)		3.29			0.14		(1.31	)		0.23
Less distributions from:
Net investment income			—		0.12			0.07			0.01		0.02			0.02
Net realized gain			—		0.79			—			—		0.01			0.23
Total distributions			—		0.91			0.07			0.01		0.03			0.25
Net asset value, end of year		$	9.67	$	8.27		$	11.09		$	7.87	$	7.74		$	9.08
Total return (%)*			16.93		(17.45	)		41.89			1.82		(14.37	)		2.62
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.30		1.27			1.40			1.54		1.54			1.60
Expenses, net of waivers and reimbursements			1.25		1.27			1.25			1.30		1.29			1.40
Net investment income (loss), before waivers and reimbursements			1.00		0.58			0.09			0.28		0.28			0.64
Net investment income (loss), net of waivers and reimbursements			1.05		0.58			0.24			0.52		0.53			0.84
Class I net assets at the end of the year (in thousands)		$	43,233	$	34,786		$	47,666		$	30,346	$	32,862		$	28,475
Portfolio turnover rate (%)*			13		52			59			135		110			131

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

174 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Leaders Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015			2014
Net asset value, beginning of year		$	8.26	$	11.09		$	7.86	$	7.74	$	9.07		$	9.10
Income (loss) from investment operations:
Net investment income (loss)			0.05		0.07			0.03		0.03		0.04			0.08
Net realized and unrealized gain (loss) on investments			1.35		(1.98	)		3.28		0.10		(1.33	)		0.16
Total from investment operations			1.40		(1.91	)		3.31		0.13		(1.29	)		0.24
Less distributions from:
Net investment income			—		0.13			0.08		0.01		0.03			0.04
Net realized gain			—		0.79			—		—		0.01			0.23
Total distributions			—		0.92			0.08		0.01		0.04			0.27
Net asset value, end of year		$	9.66	$	8.26		$	11.09	$	7.86	$	7.74		$	9.07
Total return (%)*			16.95		(17.46	)		42.15		1.74		(14.24	)		2.68
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.24		1.20			1.19		1.34		1.35			1.42
Expenses, net of waivers and reimbursements			1.20		1.20			1.19		1.25		1.25			1.25
Net investment income (loss), before waivers and reimbursements			1.00		0.71			0.33		0.30		0.39			0.66
Net investment income (loss), net of waivers and reimbursements			1.04		0.71			0.33		0.39		0.49			0.83
Class R6 net assets at the end of the year (in thousands)		$	178,570	$	161,889		$	427,480	$	272,678	$	93,217		$	75,875
Portfolio turnover rate (%)*			13		52			59		135		110			131

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 175

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Growth Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	11.14	$	16.20		$	10.99		$	10.85	$	12.91		$	13.28
Income (loss) from investment operations:
Net investment income (loss)			0.05		0.01			(0.02	)		0.03		0.04			0.08
Net realized and unrealized gain (loss) on investments			1.71		(3.49	)		5.35			0.13		(1.98	)		0.37
Total from investment operations			1.76		(3.48	)		5.33			0.16		(1.94	)		0.45
Less distributions from:
Net investment income			—		0.11			0.12			0.02		—			0.08
Net realized gain			—		1.47			—			—		0.12			0.74
Total distributions			—		1.58			0.12			0.02		0.12			0.82
Net asset value, end of year		$	12.90	$	11.14		$	16.20		$	10.99	$	10.85		$	12.91
Total return (%)*			15.80		(21.61	)		48.53			1.49		(15.03	)		3.40
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.52		1.52			1.65			1.65		1.65			1.64
Expenses, net of waivers and reimbursements			1.52		1.52			1.50			1.50		1.50			1.64
Net investment income (loss), before waivers and reimbursements			0.91		0.09			(0.29	)		0.13		0.18			0.55
Net investment income (loss), net of waivers and reimbursements			0.91		0.09			(0.14	)		0.28		0.33			0.55
Class N net assets at the end of the year (in thousands)		$	7,833	$	7,103		$	10,479		$	8,488	$	9,367		$	12,638
Portfolio turnover rate (%)*			39		113			91			105		121			101
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	11.25	$	16.36		$	11.10		$	10.96	$	13.01		$	13.38
Income (loss) from investment operations:
Net investment income (loss)			0.07		0.05			0.01			0.06		0.07			0.11
Net realized and unrealized gain (loss) on investments			1.72		(3.52	)		5.40			0.13		(2.00	)		0.37
Total from investment operations			1.79		(3.47	)		5.41			0.19		(1.93	)		0.48
Less distributions from:
Net investment income			—		0.17			0.15			0.05		—			0.11
Net realized gain			—		1.47			—			—		0.12			0.74
Total distributions			—		1.64			0.15			0.05		0.12			0.85
Net asset value, end of year		$	13.04	$	11.25		$	16.36		$	11.10	$	10.96		$	13.01
Total return (%)*			15.91		(21.37	)		48.83			1.73		(14.83	)		3.65
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.27		1.27			1.42			1.41		1.40			1.40
Expenses, net of waivers and reimbursements			1.27		1.27			1.27			1.26		1.25			1.40
Net investment income (loss), before waivers and reimbursements			1.10		0.34			(0.07	)		0.38		0.43			0.79
Net investment income (loss), net of waivers and reimbursements			1.10		0.34			0.08			0.53		0.58			0.79
Class I net assets at the end of the year (in thousands)		$	74,224	$	79,427		$	129,481		$	93,668	$	130,491		$	166,488
Portfolio turnover rate (%)*			39		113			91			105		121			101

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

176 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Growth Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015			2014
Net asset value, beginning of year		$	11.35	$	16.49		$	11.18	$	11.05	$	13.09		$	13.46
Income (loss) from investment operations:
Net investment income (loss)			0.08		0.07			0.02		0.07		0.08			0.14
Net realized and unrealized gain (loss) on investments			1.73		(3.56	)		5.46		0.12		(2.00	)		0.37
Total from investment operations			1.81		(3.49	)		5.48		0.19		(1.92	)		0.51
Less distributions from:
Net investment income			—		0.18			0.17		0.06		—			0.14
Net realized gain			—		1.47			—		—		0.12			0.74
Total distributions			—		1.65			0.17		0.06		0.12			0.88
Net asset value, end of year		$	13.16	$	11.35		$	16.49	$	11.18	$	11.05		$	13.09
Total return (%)*			15.95		(21.29	)		49.06		1.71		(14.67	)		3.85
Ratios to average daily net assets (%)**:
Expenses			1.19		1.19			1.17		1.19		1.17			1.18
Net investment income (loss)			1.23		0.46			0.17		0.60		0.61			1.00
Class R6 net assets at the end of the year (in thousands)		$	720,273	$	654,441		$	1,178,853	$	831,587	$	739,253		$	806,708
Portfolio turnover rate (%)*			39		113			91		105		121			101

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 177

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Small Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	13.96		$	18.66		$	13.73		$	14.84		$	16.52		$	15.12
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.02	)		0.01			0.09			(0.01	)		0.04
Net realized and unrealized gain (loss) on investments			1.25			(4.38	)		5.46			(0.88	)		(1.05	)		2.13
Total from investment operations			1.24			(4.40	)		5.47			(0.79	)		(1.06	)		2.17
Less distributions from:
Net investment income			—			—			0.50			0.32			—			0.03
Net realized gain			—			0.30			0.04			—			0.62			0.74
Total distributions			—			0.30			0.54			0.32			0.62			0.77
Net asset value, end of year		$	15.20		$	13.96		$	18.66		$	13.73		$	14.84		$	16.52
Total return (%)*			8.88			(23.57	)		40.09			(5.33	)		(6.40	)		14.41
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.78			1.70			1.83			1.82			1.94			1.74
Expenses, net of waivers and reimbursements			1.55			1.58			1.64			1.61			1.65			1.65
Net investment income (loss), before waivers and reimbursements			(0.42	)		(0.22	)		(0.11	)		0.41			(0.35	)		0.12
Net investment income (loss), net of waivers and reimbursements			(0.19	)		(0.10	)		0.08			0.62			(0.06	)		0.21
Class N net assets at the end of the year (in thousands)		$	5,816		$	8,977		$	15,082		$	9,263		$	11,306		$	10,745
Portfolio turnover rate (%)*			86			187			183			157			167			124
	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2019			2018			2017			2016			2015			2014
Net asset value, beginning of year		$	14.03		$	18.73		$	13.77		$	14.90		$	16.52		$	15.13
Income (loss) from investment operations:
Net investment income (loss)			0.01			0.03			0.08			0.13			0.05			0.02
Net realized and unrealized gain (loss) on investments			1.26			(4.41	)		5.47			(0.89	)		(1.05	)		2.20
Total from investment operations			1.27			(4.38	)		5.55			(0.76	)		(1.00	)		2.22
Less distributions from:
Net investment income			—			0.02			0.55			0.37			—			0.09
Net realized gain			—			0.30			0.04			—			0.62			0.74
Total distributions			—			0.32			0.59			0.37			0.62			0.83
Net asset value, end of year		$	15.30		$	14.03		$	18.73		$	13.77		$	14.90		$	16.52
Total return (%)*			8.97			(23.31	)		40.53			(5.11	)		(6.03	)		14.73
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.46			1.38			1.50			1.51			1.52			1.49
Expenses, net of waivers and reimbursements			1.30			1.33			1.31			1.30			1.31			1.40
Net investment income (loss), before waivers and reimbursements			(0.05	)		0.13			0.30			0.66			0.09			0.06
Net investment income (loss), net of waivers and reimbursements			0.11			0.18			0.49			0.87			0.30			0.15
Class I net assets at the end of the year (in thousands)		$	155,857		$	169,770		$	282,620		$	147,949		$	162,375		$	119,662
Portfolio turnover rate (%)*			86			187			183			157			167			124

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

178 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Emerging Markets Small Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016			2015			2014
Net asset value, beginning of year		$	14.06	$	18.76		$	13.79	$	14.92		$	16.53		$	15.14
Income (loss) from investment operations:
Net investment income (loss)			0.02		0.05			0.10		0.14			0.06			0.06
Net realized and unrealized gain (loss) on investments			1.25		(4.41	)		5.47		(0.89	)		(1.05	)		2.18
Total from investment operations			1.27		(4.36	)		5.57		(0.75	)		(0.99	)		2.24
Less distributions from:
Net investment income			—		0.04			0.56		0.38			0.00	^		0.11
Net realized gain			—		0.30			0.04		—			0.62			0.74
Total distributions			—		0.34			0.60		0.38			0.62			0.85
Net asset value, end of year		$	15.33	$	14.06		$	18.76	$	13.79		$	14.92		$	16.53
Total return (%)*			9.03		(23.24	)		40.62		(5.05	)		(5.97	)		14.85
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.37		1.30			1.29		1.31			1.31			1.34
Expenses, net of waivers and reimbursements			1.25		1.25			1.25		1.25			1.25			1.25
Net investment income (loss), before waivers and reimbursements			0.10		0.22			0.53		0.88			0.28			0.28
Net investment income (loss), net of waivers and reimbursements			0.22		0.27			0.57		0.94			0.34			0.37
Class R6 net assets at the end of the year (in thousands)		$	120,319	$	98,188		$	166,927	$	125,650		$	123,160		$	123,496
Portfolio turnover rate (%)*			86		187			183		157			167			124

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 179

Financial Highlights— For a share outstanding throughout each period

Bond Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015			2014
Net asset value, beginning of year		$	9.75	$	10.41		$	10.41	$	10.34	$	10.74		$	10.60
Income (loss) from investment operations:
Net investment income (loss)			0.15		0.31			0.27		0.27		0.27			0.31
Net realized and unrealized gain (loss) on investments			0.63		(0.56	)		0.12		0.18		(0.29	)		0.23
Total from investment operations			0.78		(0.25	)		0.39		0.45		(0.02	)		0.54
Less distributions from:
Net investment income			0.21		0.41			0.39		0.38		0.38			0.40
Net realized gain			—		—			—		—		—			0.00	^
Total distributions			0.21		0.41			0.39		0.38		0.38			0.40
Net asset value, end of year		$	10.32	$	9.75		$	10.41	$	10.41	$	10.34		$	10.74
Total return (%)*			8.05		(2.42	)		3.83		4.40		(0.23	)		5.10
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.69		0.69			0.82		0.82		0.79			0.85
Expenses, net of waivers and reimbursements			0.60		0.62			0.65		0.65		0.61			0.65
Net investment income (loss), before waivers and reimbursements			3.03		3.01			2.40		2.43		2.42			2.70
Net investment income (loss), net of waivers and reimbursements			3.12		3.08			2.57		2.60		2.60			2.90
Class N net assets at the end of the year (in thousands)		$	67,493	$	70,253		$	83,662	$	125,866	$	139,303		$	16,720
Portfolio turnover rate (%)*			27		40			17		17		32			35
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015			2014
Net asset value, beginning of year		$	9.65	$	10.31		$	10.30	$	10.24	$	10.64		$	10.49
Income (loss) from investment operations:
Net investment income (loss)			0.16		0.32			0.29		0.30		0.31			0.33
Net realized and unrealized gain (loss) on investments			0.61		(0.56	)		0.13		0.16		(0.31	)		0.23
Total from investment operations			0.77		(0.24	)		0.42		0.46		—			0.56
Less distributions from:
Net investment income			0.21		0.42			0.41		0.40		0.40			0.41
Net realized gain			—		—			—		—		—			0.00	^
Total distributions			0.21		0.42			0.41		0.40		0.40			0.41
Net asset value, end of year		$	10.21	$	9.65		$	10.31	$	10.30	$	10.24		$	10.64
Total return (%)*			8.09		(2.31	)		4.16		4.55		(0.05	)		5.37
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.47		0.46			0.60		0.58		0.59			0.60
Expenses, net of waivers and reimbursements			0.45		0.46			0.43		0.41		0.41			0.50
Net investment income (loss), before waivers and reimbursements			3.25		3.24			2.62		2.66		2.75			2.97
Net investment income (loss), net of waivers and reimbursements			3.27		3.24			2.79		2.83		2.93			3.07
Class I net assets at the end of the year (in thousands)		$	281,303	$	281,442		$	384,464	$	322,174	$	237,587		$	149,466
Portfolio turnover rate (%)*			27		40			17		17		32			35

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

180 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Bond Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017		2016		2015			2014
Net asset value, beginning of year		$	9.64	$	10.30		$	10.29	$	10.23	$	10.63		$	10.48
Income (loss) from investment operations:
Net investment income (loss)			0.16		0.33			0.30		0.30		0.32			0.34
Net realized and unrealized gain (loss) on investments			0.61		(0.56	)		0.13		0.17		(0.31	)		0.23
Total from investment operations			0.77		(0.23	)		0.43		0.47		0.01			0.57
Less distributions from:
Net investment income			0.21		0.43			0.42		0.41		0.41			0.42
Net realized gain			—		—			—		—		—			0.00	^
Total distributions			0.21		0.43			0.42		0.41		0.41			0.42
Net asset value, end of year		$	10.20	$	9.64		$	10.30	$	10.29	$	10.23		$	10.63
Total return (%)*			8.12		(2.26	)		4.24		4.61		0.01			5.53
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.40		0.38			0.37		0.37		0.38			0.41
Expenses, net of waivers and reimbursements			0.40		0.38			0.35		0.35		0.35			0.35
Net investment income (loss), before waivers and reimbursements			3.32		3.32			2.85		2.88		2.98			3.17
Net investment income (loss), net of waivers and reimbursements			3.32		3.32			2.87		2.90		3.01			3.23
Class R6 net assets at the end of the year (in thousands)		$	66,976	$	70,851		$	91,629	$	95,216	$	103,904		$	97,341
Portfolio turnover rate (%)*			27		40			17		17		32			35

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 181

Financial Highlights— For a share outstanding throughout each period

Income Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.36	$	8.72		$	8.86		$	8.90	$	9.12		$	9.11
Income (loss) from investment operations:
Net investment income (loss)			0.09		0.17			0.16			0.16		0.15			0.18
Net realized and unrealized gain (loss) on investments			0.27		(0.25	)		(0.03	)		0.06		(0.11	)		0.10
Total from investment operations			0.36		(0.08	)		0.13			0.22		0.04			0.28
Less distributions from:
Net investment income			0.14		0.28			0.27			0.26		0.26			0.27
Net realized gain			—		—			—			—		—			—
Total distributions			0.14		0.28			0.27			0.26		0.26			0.27
Net asset value, end of year		$	8.58	$	8.36		$	8.72		$	8.86	$	8.90		$	9.12
Total return (%)*			4.33		(0.86	)		1.46			2.44		0.39			3.06
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.95		0.91			0.88			0.79		0.81			0.84
Expenses, net of waivers and reimbursements			0.85		0.85			0.85			0.79		0.81			0.84
Net investment income (loss), before waivers and reimbursements			1.97		1.96			1.77			1.80		1.71			1.99
Net investment income (loss), net of waivers and reimbursements			2.07		2.02			1.80			1.80		1.71			1.99
Class N net assets at the end of the year (in thousands)		$	21,319	$	22,422		$	39,625		$	52,710	$	32,942		$	34,020
Portfolio turnover rate (%)*			51		97			37			22		21			30
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.30	$	8.66		$	8.80		$	8.83	$	9.05		$	9.05
Income (loss) from investment operations:
Net investment income (loss)			0.09		0.19			0.18			0.18		0.18			0.20
Net realized and unrealized gain (loss) on investments			0.29		(0.25	)		(0.03	)		0.06		(0.12	)		0.09
Total from investment operations			0.38		(0.06	)		0.15			0.24		0.06			0.29
Less distributions from:
Net investment income			0.15		0.30			0.29			0.27		0.28			0.29
Net realized gain			—		—			—			—		—			—
Total distributions			0.15		0.30			0.29			0.27		0.28			0.29
Net asset value, end of year		$	8.53	$	8.30		$	8.66		$	8.80	$	8.83		$	9.05
Total return (%)*			4.57		(0.69	)		1.68			2.78		0.63			3.20
Ratios to average daily net assets (%)**:
Expenses			0.70		0.65			0.62			0.57		0.55			0.59
Net investment income (loss)			2.24		2.22			2.03			2.05		1.97			2.24
Class I net assets at the end of the year (in thousands)		$	42,701	$	34,793		$	51,153		$	58,160	$	62,722		$	64,834
Portfolio turnover rate (%)*			51		97			37			22		21			30

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

182 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Income Fund

	Class R6
	(unaudited) Period Ended June 30,
	2019(a)
Net asset value, beginning of year		$	8.45
Income (loss) from investment operations:
Net investment income (loss)			(0.00	)^
Net realized and unrealized gain (loss) on investments			0.13
Total from investment operations			0.13
Less distributions from:
Net investment income			0.05
Net realized gain			—
Total distributions			0.05
Net asset value, end of year		$	8.53
Total Return (%)*			1.47
Ratios to average daily net assets (%)**:
Expenses, before of waivers and reimbursements			0.68
Expenses, net waivers and reimbursements			0.65
Net investment income (loss), before of waivers and reimbursements			(0.31	)
Net investment income (loss), net waivers and reimbursements			(0.28	)
Class R6 net assets at end of year (in thousands)		$	51
Portfolio turnover rate (%)*			51

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
(a)	For the period from May 2, 2019 (Commencement of Operations) to June 30, 2019.
^	Amount is less than $0.05 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 183

Financial Highlights— For a share outstanding throughout each period

Low Duration Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.70	$	8.92		$	9.07		$	9.16	$	9.38		$	9.52
Income (loss) from investment operations:
Net investment income (loss)			0.10		0.17			0.11			0.09		0.07			0.11
Net realized and unrealized gain (loss) on investments			0.11		(0.10	)		(0.04	)		0.02		(0.07	)		(0.00	)^
Total from investment operations			0.21		0.07			0.07			0.11		—			0.11
Less distributions from:
Net investment income			0.16		0.29			0.22			0.20		0.22			0.25
Net realized gain			—		—			—			—		—			—
Total distributions			0.16		0.29			0.22			0.20		0.22			0.25
Net asset value, end of year		$	8.75	$	8.70		$	8.92		$	9.07	$	9.16		$	9.38
Total return (%)*			2.46		0.80			0.84			1.16		0.01			1.20
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.75		0.72			0.79			0.83		0.77			0.75
Expenses, net of waivers and reimbursements			0.55		0.58			0.61			0.68		0.60			0.70
Net investment income (loss), before waivers and reimbursements			2.14		1.83			1.04			0.83		0.54			1.14
Net investment income (loss), net of waivers and reimbursements			2.34		1.97			1.22			0.98		0.71			1.19
Class N net assets at the end of the year (in thousands)		$	1,632	$	1,661		$	1,979		$	7,237	$	2,712		$	4,969
Portfolio turnover rate (%)*			82		122			109			81		106			83
	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018				2017			2016		2015			2014
Net asset value, beginning of year		$	8.70	$	8.91		$	9.07		$	9.16	$	9.37		$	9.52
Income (loss) from investment operations:
Net investment income (loss)			0.11		0.19			0.13			0.11		0.08			0.13
Net realized and unrealized gain (loss) on investments			0.11		(0.09	)		(0.05	)		0.02		(0.05	)		(0.01	)
Total from investment operations			0.22		0.10			0.08			0.13		0.03			0.12
Less distributions from:
Net investment income			0.17		0.31			0.24			0.22		0.24			0.27
Net realized gain			—		—			—			—		—			—
Total distributions			0.17		0.31			0.24			0.22		0.24			0.27
Net asset value, end of year		$	8.75	$	8.70		$	8.91		$	9.07	$	9.16		$	9.37
Total return (%)*			2.54		1.12			0.91			1.40		0.30			1.24
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.52		0.46			0.59			0.59		0.59			0.60
Expenses, net of waivers and reimbursements			0.39		0.39			0.41			0.44		0.42			0.55
Net investment income (loss), before waivers and reimbursements			2.37		2.05			1.27			1.05		0.70			1.30
Net investment income (loss), net of waivers and reimbursements			2.50		2.12			1.45			1.20		0.87			1.35
Class I net assets at the end of the year (in thousands)		$	54,744	$	56,120		$	131,186		$	219,714	$	107,137		$	104,433
Portfolio turnover rate (%)*			82		122			109			81		106			83

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.
^	Amount is less than $0.005 per share.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

184 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Low Duration Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2019		2018			2017			2016		2015			2014
Net asset value, beginning of year		$	8.70	$	8.91		$	9.07		$	9.16	$	9.38		$	9.53
Income (loss) from investment operations:
Net investment income (loss)			0.11		0.19			0.14			0.11		0.09			0.14
Net realized and unrealized gain (loss) on investments			0.11		(0.09	)		(0.05	)		0.02		(0.07	)		(0.01	)
Total from investment operations			0.22		0.10			0.09			0.13		0.02			0.13
Less distributions from:
Net investment income			0.17		0.31			0.25			0.22		0.24			0.28
Net realized gain			—		—			—			—		—			—
Total distributions			0.17		0.31			0.25			0.22		0.24			0.28
Net asset value, end of year		$	8.75	$	8.70		$	8.91		$	9.07	$	9.16		$	9.38
Total return (%)*			2.56		1.15			0.96			1.43		0.22			1.40
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.49		0.42			0.40			0.40		0.42			0.43
Expenses, net of waivers and reimbursements			0.35		0.35			0.37			0.40		0.40			0.40
Net investment income (loss), before waivers and reimbursements			2.41		2.10			1.48			1.25		0.92			1.42
Net investment income (loss), net of waivers and reimbursements			2.55		2.17			1.51			1.25		0.94			1.45
Class R6 net assets at the end of the year (in thousands)		$	43,817	$	47,585		$	99,912		$	53,122	$	21,863		$	68,095
Portfolio turnover rate (%)*			82		122			109			81		106			83

*	Rates are not annualized for periods less than a year.
**	Rates are annualized for periods less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 185

Financial Highlights— For a share outstanding throughout each period

Macro Allocation Fund

	Class N
	(unaudited) Period Ended June 30,			Periods Ended December 31,													Year Ended October 31,
		2019			2018			2017		2016		2015			2014(a)		2014
Net asset value, beginning of year		$	11.41	$	11.84		$	11.34	$	11.32	$	12.14		$	13.07			$	12.61
Income (loss) from investment operations:
Net investment income (loss)			0.04		0.08			0.06		0.04		0.04			0.04				0.02
Net realized and unrealized gain (loss) on investments			0.24		(0.24	)		0.51		0.19		(0.80	)		(0.31	)			0.76
Total from investment operations			0.28		(0.16	)		0.57		0.23		(0.76	)		(0.27	)			0.78
Less distributions from:
Net investment income			—		0.27			0.07		0.21		0.06			0.66				0.09
Net realized gain			—		—			—		—		—			—				0.23
Total distributions			—		0.27			0.07		0.21		0.06			0.66				0.32
Net asset value, end of year		$	11.69	$	11.41		$	11.84	$	11.34	$	11.32		$	12.14			$	13.07
Total return (%)*			2.45		(1.30	)		5.06		2.01		(6.24	)		(2.00	)			6.34
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.23		1.30			1.52		1.38		1.42			1.46				1.60
Expenses, net of waivers and reimbursements			1.23		1.30			1.37		1.23		1.27			1.38				1.47
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			1.21		1.28			1.31		1.23		1.27			1.35				1.35
Net investment income (loss), before waivers and reimbursements			0.73		0.66			0.35		0.17		0.17			1.98				0.07
Net investment income (loss), net of waivers and reimbursements			0.73		0.66			0.50		0.32		0.32			2.06				0.20
Class N net assets at the end of the year (in thousands)		$	37,918	$	43,463		$	41,483	$	61,376	$	150,606		$	150,778			$	150,785
Portfolio turnover rate (%)*			12		36			43		50		34			17				59
	Class I
	(unaudited) Period Ended June 30,			Periods Ended December 31,													Year Ended October 31,
		2019			2018			2017		2016		2015			2014(a)		2014
Net asset value, beginning of year		$	11.38	$	11.88		$	11.38	$	11.38	$	12.22		$	13.15			$	12.66
Income (loss) from investment operations:
Net investment income (loss)			0.06		0.11			0.11		0.08		0.09			0.05				0.04
Net realized and unrealized gain (loss) on investments			0.24		(0.24	)		0.51		0.18		(0.82	)		(0.31	)			0.78
Total from investment operations			0.30		(0.13	)		0.62		0.26		(0.73	)		(0.26	)			0.82
Less distributions from:
Net investment income			—		0.37			0.12		0.26		0.11			0.67				0.10
Net realized gain			—		—			—		—		—			—				0.23
Total distributions			—		0.37			0.12		0.26		0.11			0.67				0.33
Net asset value, end of year		$	11.68	$	11.38		$	11.88	$	11.38	$	11.38		$	12.22			$	13.15
Total return (%)*			2.64		(1.08	)		5.50		2.26		(6.00	)		(1.94	)			6.60
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.98		0.99			1.17		1.12		1.14			1.10				1.27
Expenses, net of waivers and reimbursements			0.98		0.99			1.02		0.97		0.99			1.10				1.22
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			0.96		0.97			0.96		0.97		0.98			1.07				1.10
Net investment income (loss), before waivers and reimbursements			1.02		0.95			0.75		0.52		0.58			2.33				0.27
Net investment income (loss), net of waivers and reimbursements			1.02		0.95			0.90		0.67		0.73			2.33				0.32
Class I net assets at the end of the year (in thousands)		$	440,655	$	486,543		$	780,075	$	937,244	$	1,155,051		$	649,756			$	617,531
Portfolio turnover rate (%)*			12		36			43		50		34			17				59

(a)	For the period November 1, 2014 to December 31, 2014.
*	Rates are not annualized for periods that are less than a year.
**	Rates are annualized for periods that are less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

186 Semiannual Report June 30, 2019

Financial Highlights— For a share outstanding throughout each period

Macro Allocation Fund

	Class R6
	(unaudited) Period Ended June 30,			Periods Ended December 31,													Year Ended October 31,
		2019			2018			2017		2016		2015			2014(a)		2014
Net asset value, beginning of year		$	11.38	$	11.89		$	11.40	$	11.39	$	12.23		$	13.16			$	12.66
Income (loss) from investment operations:
Net investment income (loss)			0.07		0.13			0.12		0.09		0.12			0.05				0.04
Net realized and unrealized gain (loss) on investments			0.23		(0.24	)		0.51		0.19		(0.84	)		(0.31	)			0.79
Total from investment operations			0.30		(0.11	)		0.63		0.28		(0.72	)		(0.26	)			0.83
Less distributions from:
Net investment income			—		0.40			0.14		0.27		0.12			0.67				0.10
Net realized gain			—		—			—		—		—			—				0.23
Total distributions			—		0.40			0.14		0.27		0.12			0.67				0.33
Net asset value, end of year		$	11.68	$	11.38		$	11.89	$	11.40	$	11.39		$	12.23			$	13.16
Total return (%)*			2.64		(0.94	)		5.51		2.44		(5.92	)		(1.91	)			6.71
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.90		0.91			0.92		0.89		0.90			0.91				1.05
Expenses, net of waivers and reimbursements			0.90		0.91			0.92		0.89		0.90			0.91				1.05
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			0.88		0.89			0.86		0.89		0.90			0.88				0.93
Net investment income (loss), before waivers and reimbursements			1.18		1.10			1.04		0.81		0.95			2.54				0.32
Net investment income (loss), net of waivers and reimbursements			1.18		1.10			1.04		0.81		0.95			2.54				0.32
Class R6 net assets at the end of the year (in thousands)		$	411,704	$	391,812		$	487,082	$	582,298	$	426,230		$	158,152			$	150,447
Portfolio turnover rate (%)*			12		36			43		50		34			17				59

(a)	For the period November 1, 2014 to December 31, 2014.
*	Rates are not annualized for periods that are less than a year.
**	Rates are annualized for periods that are less than a year.

Note: Net investment income (loss) per share is based on the average shares outstanding during the year.

Performance cited represents past performance. Past performance does not guarantee future results and current performance may be lower or higher than the data quoted. Results shown are annual returns, which assume reinvestment of dividends and capital gains. Investment returns and principal will fluctuate and you may have a gain or loss when you sell shares. For the most current month-end performance information, please call 1-800-742-7272 or visit our Web site atwww.williamblairfunds.com.

June 30, 2019 William Blair Funds 187

Renewal of the Management Agreement

On April 25, 2019, the Board of Trustees (the “Board”) of the William Blair Funds (the “Trust”) including the Trustees who are not “interested persons” of the Trust as defined by the Investment Company Act of 1940, as amended (the “Independent Trustees”), approved the renewal for an additional one-year term of the Trust’s Management Agreement with William Blair Investment Management, LLC (“WBIM” or the “Adviser”) on behalf of each of the William Blair Funds (each, a “Fund” and collectively, the “Funds”). In deciding to approve the renewal of the Management Agreement, the Board did not identify any single factor or group of factors as all important or controlling and considered all factors together. The Board did not allot a particular weight to any one factor or group of factors.

The information in this summary outlines the Board’s considerations associated with its renewal of the Management Agreement. In connection with its deliberations regarding the continuation of the Management Agreement, the Board considered such information and factors as it believed to be relevant. As described below, the Board considered the nature, quality and extent of the services performed by the Adviser under the Management Agreement; the investment performance of each Fund and the Adviser; comparative management fees and expense ratios as prepared by an independent provider (Broadridge); the estimated profitability realized by the Adviser; the extent to which the Adviser realizes economies of scale as a Fund grows; and whether fall-out benefits are being realized by the Adviser. In addition, the Independent Trustees discussed the renewal of the Management Agreement with Trust management and in private sessions with independent legal counsel at which no representatives of the Adviser were present.

The Board, including the Independent Trustees, considered the renewal of the Management Agreement pursuant to a process that concluded at the Board’s April 25, 2019 meeting. In preparation for the review process, the Independent Trustees considered the type and nature of information to be requested, and independent legal counsel sent a formal request for information to the Adviser. The Adviser provided extensive information in response to the request. After reviewing the information received, the Independent Trustees requested supplemental information, which the Adviser provided. The Board also received a memorandum from legal counsel advising it of their duties and responsibilities in connection with the consideration of the Management Agreement. The Independent Trustees reviewed comparative performance for a performance peer universe and peer group of funds and comparative management fees and expense ratios for an expense peer group and an expense peer universe of funds provided by Broadridge for each Fund. In addition, the Independent Trustees considered: (1) the nature, quality and extent of services provided by the Adviser; (2) information comparing the performance of each Fund to one or more relevant securities indexes; (3) information comparing management fees of each Fund to fees charged by the Adviser to other funds and client accounts with similar investment strategies; (4) the estimated allocated direct or indirect costs of services provided and estimated profits realized by the Adviser for both the Trust as a whole and each Fund individually; and (5) information describing other benefits to the Adviser and its affiliate, William Blair & Company, L.L.C. (the “Distributor,” and collectively with the Adviser, “William Blair”), resulting from their relationship with the Funds. The Independent Trustees also noted that they receive information from the Adviser regarding the Funds throughout the year in connection with regular Board meetings, including presentations from portfolio managers. In addition, the Adviser made an in-person presentation to the Board regarding the contract review information, including addressing the supplemental information requests, and answered questions from the Independent Trustees. The Board, including the Independent Trustees, determined that, given the totality of the information provided with respect to the Management Agreement, the Board had received sufficient information to renew the Management Agreement. The Independent Trustees noted that in evaluating the Management Agreement, they were taking into account their accumulated experience as Board members in working with the Adviser on matters relating to the Funds. Based on their review, the Independent Trustees concluded that it was in the best interest of each Fund to renew the Management Agreement and, accordingly, recommended to the Board of the Trust the renewal of the Management Agreement for each Fund. The Board considered the recommendation of the Independent Trustees along with other factors that the Board deemed relevant.

Nature, Quality and Extent of Services.In evaluating the nature, quality and extent of the services provided by the Adviser to the Funds, the Board noted that the Adviser is a quality firm with a reputation for integrity and honesty that employs high-quality people and has a long association with the Funds, in each case other than the Growth Fund, since the inception of the Funds. The Board believes that a long-term relationship with a capable, conscientious adviser is in the best interests of shareholders and that shareholders have invested in the Funds knowing that the Adviser manages the Funds and knowing the management fees. The Board considered the Adviser’s fundamental research approach in actively managed, process oriented investing. The Board considered biographical information about the Trust’s officers, other Adviser personnel and the Funds’ portfolio managers, including information on the portfolio managers’ personal investments in the Fund(s) they manage. The Board also considered the administrative services performed by the Adviser, financial information regarding the Adviser, the Adviser’s execution quality and use of soft dollars, risk management oversight, compliance program and the expense limitations proposed for each of the Funds’ share classes. The Board also considered the nature, quality and extent of services that the Adviser provides to the Funds compared to the services that the Adviser provides to other clients. The Board noted that the

188 Semiannual Report June 30, 2019

Adviser pays the compensation of all of the officers and the interested Trustees of the Trust. Based upon all relevant factors, the Board concluded that the nature, quality and extent of the services provided by the Adviser to each Fund were appropriate.

Performance.The Board reviewed information on the annualized total returns of each share class of the Funds for the one-, three-, five- and ten-year periods ended December 31, 2018, as applicable, along with annualized total return information for a Morningstar performance peer universe of funds and one or more benchmark securities indexes. The Morningstar performance peer universe for each Fund included all funds in the same Morningstar category as the Fund. For purposes of this report, Class N shares were used for comparison purposes as the Board noted that Class N shares have additional costs related to distribution and shareholder services provided and therefore provide a more conservative representation of Fund performance.

The Board considered that the Adviser seeks to provide superior performance over the long term and was committed to managing each Fund consistently with the Fund’s stated investment strategies and that at times relative performance will be affected by whether the market environment favors or disfavors particular investments, styles and/or market capitalizations. The Board considered that since the Global Financial Crisis in 2008-2009, the low interest rate environment globally has fostered relatively low stock market volatility, with notable bouts of volatility in 2015, 2016, and 2018. The Board concluded that the Adviser had managed the equity Funds in the U.S., International and Emerging Markets growth strategies consistent with its disciplined quality growth philosophy. Based on the information provided, the Board considered the following with respect to the total returns of each Fund.

Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe for the one-year period, the same as the average of its Morningstar performance peer universe for the three-year period and below the average of its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board also considered that the Fund outperformed the benchmark (Russell 3000^®Growth Index) for the one-year period and underperformed the benchmark for the three- and five-year periods ended December 31, 2018.

Large Cap Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (Russell 1000^®Growth Index) for the one-, three- and five-year periods ended December 31, 2018.

Mid Cap Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe for the one-year period and below the average of its Morningstar performance peer universe for the three- and five- year periods ended December 31, 2018. The Board also considered that the Fund outperformed the benchmark (Russell Midcap^®Growth Index) for the one-year period and underperformed the benchmark for the three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that stock selection in certain sectors detracted from the Fund’s performance. The Board considered changes to the Adviser’s portfolio management team, the addition of analysts to the investment team and the Adviser’s other investment team modifications over the past three years to align coverage by sector and market capitalization, with the goal of improving relative performance.

Small-Mid Cap Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (Russell 2500^TMGrowth Index) for the one-, three- and five-year periods ended December 31, 2018.

Small-Mid Cap Value Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (Russell 2500^TMValue Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s view that while better stock selection would have lessened underperformance over the three- and five- year periods, that the rally in deeper value stocks and the outperformance of smaller cap and lower quality stocks contributed to underperformance.

Small Cap Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (Russell 2000^®Growth Index) for the one-, three- and five-year periods ended December 31, 2018.

Small Cap Value Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (Russell 2000^®Value Index) for the one-, three- and five- year periods ended December 31, 2018. The Board considered the Adviser’s view that while better stock selection would have lessened underperformance over the three- and five- year periods, that the rally in deeper value stocks and the outperformance of smaller cap and lower quality stocks contributed to underperformance.

Global Leaders Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe for the one-, three- and five-year periods ended December 31, 2018. The Board also considered that the Fund

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outperformed the benchmark (MSCI All Country World IMI (net) Index) for the one- and five-year periods and underperformed the benchmark for the three-year period ended December 31, 2018.

International Leaders Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (MSCI All Country World Ex-U.S. IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2018.

International Developed Plus Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (MSCI World Ex-U.S. (net) Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered that the Adviser proposed to liquidate the Fund.

Institutional International Developed Plus Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one-, three- and five-year periods ended December 31, 2018. The Board also considered that the Fund underperformed the benchmark (MSCI World Ex-U.S. (net) Index) for the one- and three- year periods and outperformed the benchmark for the five-year period ended December 31, 2018. The Board considered that the Adviser proposed to liquidate the Fund.

International Growth Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (MSCI All Country World Ex-U.S. IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that underperformance in 2018 primarily occurred in the second half of the year as companies with low valuations and poor earnings trends led the index amid the broad sell off in global equity markets and that weak stock selection in certain sectors and countries detracted from performance in 2016. The Board also considered that the Fund outperformed the benchmark in 2017, 2015 and 2014.

Institutional International Growth Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (MSCI All Country World Ex-U.S. IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that underperformance in 2018 primarily occurred in the second half of the year as companies with low valuations and poor earnings trends led the index amid the broad sell off in global equity markets and that weak stock selection in certain sectors and countries detracted from performance in 2016. The Board also considered that the Fund outperformed the benchmark in 2017, 2015 and 2014.

International Small Cap Growth Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (MSCI All Country World Ex-U.S. Small Cap (net) Index) for the one-, three-and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that the Fund’s underperformance was driven by relative weakness in calendar years 2018, 2016 and 2014 attributable to weak stock selection in certain sectors, offsetting the positive effects of 2015 and 2017 outperformance. The Board also considered the investment process improvements and portfolio construction changes that had been implemented.

Emerging Markets Leaders Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one- and three-year periods and above the average of its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board considered that the Fund underperformed the benchmark (MSCI Emerging Markets (net) Index) for the one-, three- and five-year periods ended December 31, 2018. The Board also considered that the Adviser attributed underperformance in part to stock selection and to market dynamics that did not favor the Adviser’s quality growth investing style.

Emerging Markets Growth Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one- and three-year periods and above the average of its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board also considered that the Fund underperformed the benchmark (MSCI Emerging Markets IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2018. The Board also considered the Adviser’s view that relative performance was significantly negatively impacted by outlier quarters in 2016 and 2018 characterized as style headwinds.

Emerging Markets Small Cap Growth Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one- and three-year periods and above the average of its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board also considered that the Fund underperformed the benchmark for the one- and three-year periods and outperformed the benchmark (MSCI Emerging Markets Small Cap (net) Index) for the five-year period ended December 31, 2018. The Board also considered the Adviser’s report that underperformance was largely driven by exogenous factors that negatively impacted the Fund’s relative performance in the third quarter of 2018, and style headwinds in 2016.

190 Semiannual Report June 30, 2019

Bond Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe and the benchmark (Bloomberg Barclays U.S. Aggregate Bond Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that during the fourth quarter of 2018, security selection themes impacted performance negatively and overwhelmed the one-, three-, and five-year results.

Income Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one- and three- year periods and above its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board also considered that the Fund underperformed the benchmark (Bloomberg Barclays Intermediate Government/Credit Bond Index) for the one-, three- and five-year periods ended December 31, 2018. The Board considered the Adviser’s report that the Fund’s investment limitation on lower quality securities negatively impacted the Fund’s benchmark-relative and peer group performance due to the outperformance of lower quality securities over the one-, three-, and five-year periods.

Low Duration Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one-, three- and five-year periods ended December 31, 2018. The Board also considered that the Fund underperformed the benchmark (Bank of America Merrill Lynch 1-Year U.S. Treasury Note Index) for the one- and three-year periods and outperformed the benchmark for the five-year period ended December 31, 2018. The Board considered the Adviser’s report that the Fund’s exposure to short term securities with longer durations compared to the benchmark negatively impacted the Fund’s performance in 2016 and 2018 when interest rates increased.

Macro Allocation Fund. The Board considered that the Fund’s total return was above its Morningstar performance peer universe for the one- and three-year periods and below the average of its Morningstar performance peer universe for the five-year period ended December 31, 2018. The Board also considered that the Fund outperformed the benchmark (Bank of America Merrill Lynch 3-Month U.S. Treasury Bill Index) for the three-year period and underperformed the benchmark for the one- and five-year periods ended December 31, 2018.

Management Fees.The Board reviewed each Fund’s management fee and reviewed information comparing the management fee to those of an expense peer group and an expense peer universe of funds provided by Broadridge for each share class of the Funds. The Broadridge expense peer group for Class N shares of each Fund (“Class N Broadridge Expense Group”) consisted of a group of retail no-load funds with a similar investment strategy and asset size, as classified by Broadridge. The Broadridge expense peer group for Class I and the Institutional Class of each Fund (“Class I Broadridge Expense Group” and “Institutional Class Broadridge Expense Group,” respectively) consisted of a group of institutional funds with a similar investment strategy and asset size, as classified by Broadridge. The Broadridge expense peer universe for each share class of each Fund consisted of the Fund’s Broadridge expense peer group and all other no-load funds with an investment strategy as classified by Broadridge similar to the Fund’s. In considering the Broadridge information and giving effect to the contractual management fee reductions proposed by the Adviser, the Board noted that the contractual management fees for the Emerging Markets Small Cap Growth Fund, the Bond Fund, and the Income Fund were below the average contractual management fee of their Class I Broadridge Expense Group. The Board also noted that the contractual management fees for the Growth Fund, the Large Cap Growth Fund, the Mid Cap Growth Fund, the Small-Mid Cap Growth Fund, the Small Mid Cap Value Fund, the Small Cap Growth Fund, the Small Cap Value Fund, the Global Leaders Fund, the International Leaders Fund, the International Developed Plus Fund, the International Growth Fund, the International Small Cap Growth Fund, the Emerging Markets Leaders Fund, the Emerging Markets Growth Fund, the Low Duration Fund and the Macro Allocation Fund were above the average contractual management fee of their Class I Broadridge Expense Group. The Board also considered the Adviser’s proposal to reduce the contractual management fee for the Large Cap Growth Fund, Mid Cap Growth Fund, Small-Mid Cap Value Fund, Global Leaders Fund, and International Leaders Fund.

In considering the management fee for the Institutional International Developed Plus Fund and the Institutional International Growth Fund, which do not have Class I shares, the Board noted that the contractual management fees for each Fund were above the average contractual management fee of their Institutional Class Broadridge Expense Group.

The Board noted the current and proposed contractual expense limitations for the Funds and further noted that the Adviser proposed reducing the contractual limit on operating expenses for the Large Cap Growth Fund, Global Leaders Fund, International Leaders Fund and Emerging Markets Leaders Fund. The Board considered that the Adviser proposed to contractually limit operating expenses until April 30, 2020 for each share class of the Funds including the new Class R6. The Board considered the amount of management fees waived and other expenses reimbursed by the Adviser on behalf of the Funds in 2018, noting that the Adviser waived its entire management fee for and reimbursed other expenses to the Small-Mid Cap Value Fund. The Board also considered that the shareholder administration fee applicable to Class N and Class I had been reduced to zero.

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For each Fund, the Board also reviewed amounts charged by the Adviser to other pooled investment vehicles, including other registered funds for which the Adviser acts as a sub-adviser, and the Adviser’s fee schedule for institutional accounts. With respect to other pooled investment vehicles and institutional accounts, the Board considered the Adviser’s statements to the effect that the level of services provided to the Funds and the regulatory responsibilities associated with sponsoring registered investment companies were greater as compared to the work involved for other pooled investment vehicles, including other registered funds for which the Adviser acts as a sub-adviser, and institutional accounts. In addition, the Board considered the Adviser’s statements to the effect that institutional accounts are distributed differently, operate under different investment and regulatory structures and have different business risks as compared to the Funds and that there are responsibilities and duties involved in sponsoring a registered fund that are not present in sub-advising a registered fund.

On the basis of all the information provided, the Board concluded that each Fund’s management fee, coupled with the applicable expense limitations, was reasonable.

Profitability.With respect to the profitability of the Management Agreement to the Adviser, the Board considered the overall fees paid under the Management Agreement, including the estimated allocated costs of the services provided, management fees waived and other expenses reimbursed, if any, and profits realized by the Adviser from its relationship with the Trust as a whole and each Fund individually. The Board concluded that the estimated profits realized by the Adviser were not unreasonable.

Economies of Scale.The Board considered the extent to which economies of scale would be realized as the Funds grow and whether fee levels reflect these economies of scale for the benefit of investors. The Board noted the Adviser’s statements to the effect that the resources required for the Adviser’s fundamental investment process typically increase as a Fund increases in size. The Board also considered that certain of the Funds were part of investment strategies that were capacity constrained by the Adviser so that opportunities for economies of scale were limited. The Board further considered that of the Funds that are subject to capacity constraints, the International Growth Fund, Institutional International Growth Fund, International Small Cap Growth Fund, Emerging Markets Growth Fund and Emerging Markets Small Cap Growth Fund are closed.

In considering whether fee levels reflect economies of scale for the benefit of Fund investors, the Board considered each Fund’s asset size, management fee breakpoints for applicable Funds, the expense limitations in place for each Fund and the proposed reduction in management fees and/or expense limits for certain Funds and each Fund’s expense ratios. The Board concluded that in the aggregate the Funds’ fee levels reasonably reflect appropriate recognition of economies of scale.

Other Benefits.The Board considered benefits derived by the Adviser and its affiliates from their relationship with the Funds, including (1) receipt of research from brokerage firms; (2) soft dollars, which pertain primarily to the Funds investing in equity securities; (3) reimbursement of some intermediary fees in the nature of sub-transfer agency fees; (4) fees from Class N shares of the Funds to the Distributor pursuant to the Rule 12b-1 Plan, nearly all of which are paid to third parties; and (5) favorable media coverage. The Board determined that management fees were reasonable in light of these benefits.

Conclusion.Based upon all of the information considered and the conclusions reached, the Board determined that the terms of the Management Agreement continue to be fair and reasonable and that the continuation of the Management Agreement is in the best interests of each Fund.

192 Semiannual Report June 30, 2019

Trustees and Officers (Unaudited).^†The trustees and officers of the William Blair Funds, their year of birth, their principal occupations during the last five years, their affiliations, if any, with William Blair, and their other significant affiliations are set forth below. The address of each officer and trustee is 150 North Riverside Plaza, Chicago, Illinois 60606.

Name and Year of Birth	Position(s)  Held with  Trust	Term of  Office(1)and  Length of  Time  Served	Principal  Occupation(s)  During Past 5 Years	Number of  Portfolios  in Trust  Complex  Overseen  by Trustee	Other Directorships  Held by Trustee  During Past 5 Years
Interested Trustees
Stephanie G. Braming, 1970(2)	Chairman of the Board and President, previously Senior Vice President	Chairman of the Board and President since 2018, and Senior Vice President 2014-2018	Global Head of Investment Management since 2017, portfolio manager (2014– 2017) and Partner, William Blair	21	Chairman, William Blair SICAV.
Arthur J. Simon, 1954(2)	Trustee	Since 2018	General Counsel and Partner, William Blair	21	Director, William Blair SICAV.
Non-Interested Trustees
Vann A. Avedisian, 1964(3)	Trustee	Since 2012	Principal, Highgate Holdings (hotel investments) (since 2009); formerly, co-founder and Managing Director, Oxford Capital Partners Inc. (1994 to 2006)	21	Potbelly Corporation (2001 to 2015)
Kathleen T. Barr, 1955	Trustee	Since 2013	Retired; formerly, President, Productive Capital Management, Inc. (registered investment adviser to public entities) and Owner, KT Barr Consulting, LLC (mutual fund and investment management consulting) (2010 to 2013); prior thereto, Chief Administrative Officer, Senior Vice President and Senior Managing Director of Allegiant Asset Management Company (merged with PNC Capital Advisors, LLC in 2009) (2004 to 2010); Chief Administrative Officer, Chief Compliance Officer and Senior Vice President of PNC Funds and PNC Advantage Funds (f/k/a Allegiant Funds) (2003 to 2010)	21	Professionally Managed Portfolios (since 2018); Council Member, Independent Directors Council; AmericaFirst Quantitative Funds (5 portfolios) (2012 to 2016)

† William Blair Investment Management, LLC and William Blair & Company, L.L.C. are collectively referred to in this section as “William Blair”, each of which is a wholly owned subsidiary of WBC Holdings, L.P., which is wholly owned by certain William Blair employees (employee owners are referred to as ‘partners’).

June 30, 2019 William Blair Funds 193

Name and Year of Birth	Position(s) Held with Trust	Term of Office(1)and Length of Time Served	Principal Occupation(s) During Past 5 Years	Number of Portfolios in Trust Complex Overseen by Trustee	Other Directorships Held by Trustee During Past 5 Years
Daniel N. Leib, 1966(4)	Trustee	Since 2016	Chief Executive Officer, Donnelley Financial Solutions, Inc. (since 2016); formerly, Executive Vice President and Chief Financial Officer, (2011 to 2016) and Group Chief Financial Officer (2009 to 2011), R.R. Donnelley  & Sons Company	21	Donnelly Financial Solutions, Inc. (since 2016)
Dorri C. McWhorter, 1973	Trustee	Since 2019	Chief Executive Officer, YWCA Metropolitan Chicago (since 2013); formerly Partner, Crowe LLP(2008-2013)(5)	21	Skyway Concession Company, LLC (since 2018); Illinois CPA Society (since 2017); American Institute of Certified Public Accountants (2013- 2016); Chicago Finance Exchange (2009-2017)
Thomas J. Skelly, 1951	Trustee	Since 2007	Advisory Board Member for various U.S. companies (since 2005); formerly, Managing Partner of various divisions at Accenture (1994-2004)	21	Mutual Trust Financial Group (provider of insurance and investment products)
Steven R. Zenz, 1954	Trustee	Since 2018	Consultant, Steven R. Zenz Consulting LLC (merger and acquisition transactions and SEC reporting and filings) (since 2011); formerly, Partner, KPMG LLP (1987-2010)(6)	21	Frankly Inc. (technology products and services for media industry) (since 2016); Insignia Systems, Inc. (in-store advertising services for consumer packaged goods manufacturers) (since 2013)

(1)	Each Trustee serves until the election and qualification of a successor, or until death, resignation or retirement, or removal as provided in the Trust’s Declaration of Trust. Retirement for Non-Interested Trustees occurs no later than at the conclusion of the first regularly scheduled Board meeting of the calendar year that occurs after the earlier of (a) the Non-Interested Trustee’s 72nd birthday or (b) the 15th anniversary of the date that the Non-Interested Trustee became a member of the Board of Trustees.
(2)	Ms. Braming and Mr. Simon are interested persons of the Trust because they are partners of William Blair, and with respect to Ms. Braming also due to her position as an officer of the Trust.
(3)	Mr. Avedisian served as a member of the Board of Directors of Potbelly Corporation (“Potbelly”) from 2001 to 2015. In October 2013, Potbelly completed an underwritten initial public offering of its common stock (the “Offering”). William Blair served as a member of the underwriting syndicate. At the time of the Offering, Mr. Avedisian, through entities he owns or controls, indirectly beneficially owned 1,607,448 shares of Potbelly common stock and warrants to purchase 241,704 shares of common stock representing approximately 8.9% of the shares before the Offering. Mr. Avedisian disclaimed beneficial ownership of the shares except to the extent of his pecuniary interest therein. Potbelly sold 8,474,869 shares and certain stockholders, including two entities affiliated with William Blair, sold 150,131 shares in the Offering at a price to the public of $14.00 per share. Neither Mr. Avedisian nor the entities he owns or controls was a selling stockholder in the Offering. A portion of the net proceeds received by Potbelly from the Offering was used to pay a previously declared cash dividend, in an aggregate amount of approximately $49.9 million, on Potbelly common and preferred shares outstanding immediately prior to the closing of the Offering, which included the outstanding shares indirectly beneficially owned by Mr. Avedisian, William Blair and two entities affiliated with William Blair.
(4)	The Funds and William Blair use Donnelley Financial Solutions, Inc. (‘’DFS’’), formerly a company of R.R. Donnelley & Sons Company (‘’RRD’’), for financial printing and other services. DFS was formed as a spin-off from RRD in October 2016 and is a public company. The Funds and William Blair in the aggregate paid DFS approximately $172,000 and $122,000 in 2017 and 2018, respectively, for the services provided. DFS’s revenue was approximately $1 billion in each of 2017 and 2018. Mr. Leib, as the Chief Executive Officer of DFS, is not directly involved in any of the services provided to the Funds or William Blair and his compensation is not materially affected by the fees DFS receives from the Funds and William Blair. The Funds and William Blair engaged RRD for financial printing and other services prior to the spin-off and the amounts involved were not material. Mr. Leib, as former Executive Vice President and Chief Financial Officer of RRD, was not directly involved in any of the services provided to the Funds or William Blair and his compensation was not materially affected by the fees RRD received from the Funds and William Blair.
(5)	As a former partner of the audit firm Crowe LLP (formerly, Crowe Horwath LLP), Ms. McWhorter receives distributions of her capital in the firm over time and those distributions are expected to be completed in March 2021. The Funds and William Blair made no payments to Crowe LLP over the past three years.
(6)	The Funds engage KPMG to provide foreign tax services in Taiwan. KPMG does not provide audit or audit-related services to the Funds. Mr. Zenz is a former partner of KPMG and receives pension/retirement funds from KPMG.

194 Semiannual Report June 30, 2019

Name and Year of Birth	Position(s) Held with Trust	Term of Office and Length of Time Served(1)	Principal Occupation(s) During Past 5 Years
Officers
Michael P. Balkin, 1959	Senior Vice President	Since 2008	Partner, William Blair
Thomas Clarke, 1968	Senior Vice President	Since 2011	Partner, William Blair (since 2014); formerly, Associate, William Blair (2011-2014)
Daniel Crowe, 1972	Senior Vice President	Since 2016	Partner, William Blair (since 2015); formerly, Associate, William Blair
Robert J. Duwa, 1967	Senior Vice President	Since 2019	Partner, William Blair
Simon Fennell, 1969	Senior Vice President	Since 2013	Partner, William Blair (since 2013); formerly, Associate, William Blair (2011-2013)
Andrew G. Flynn, 1961	Senior Vice President	Since 2013	Partner, William Blair
David C. Fording, 1967	Senior Vice President	Since 2006	Partner, William Blair
James S. Golan, 1961	Senior Vice President	Since 2005	Partner, William Blair
Chad M. Kilmer, 1975	Senior Vice President	Since 2006	Partner, William Blair
Robert C. Lanphier IV, 1956	Senior Vice President	Since 2003	Partner, William Blair
Mark T. Leslie, 1967	Senior Vice President	Since 2005	Partner, William Blair
Kenneth J. McAtamney, 1966	Senior Vice President	Since 2008	Partner, William Blair
Todd M. McClone, 1968	Senior Vice President	Since 2005	Partner, William Blair
David Merjan, 1960	Senior Vice President	Since 2008	Partner, William Blair
David S. Mitchell, 1960	Senior Vice President	Since 2003	Partner, William Blair
John C. Murphy, 1969	Senior Vice President	Since 2014	Partner, William Blair
Casey K. Preyss, 1976	Senior Vice President	Since 2015	Partner, William Blair
David P. Ricci, 1958	Senior Vice President	Since 2006	Partner, William Blair
Ward D. Sexton,  1974	Senior Vice President	Since 2016	Partner, William Blair
Brian D. Singer, 1960	Senior Vice President	Since 2011	Partner, William Blair
Christopher T. Vincent, 1956	Senior Vice President	Since 2002	Partner, William Blair

June 30, 2019 William Blair Funds 195

Name and Year of Birth	Position(s) Held with Trust	Term of Office and Length of Time Served(1)	Principal Occupation(s) During Past 5 Years
Dan Zelanzy, 1971	Senior Vice President	Since 2019	Associate, William Blair (since 2019); formerly Managing Director, AQR Capital Management (2011-2019)
Lisa D. Rusch, 1970	Vice President	Since 2018	Associate, William Blair
Paul J. Sularz, 1967	Vice President	Since 2009	Associate, William Blair (2006-2012 and since 2014); Partner, William Blair (2012-2014)
Colette M. Garavalia, 1961	Treasurer	Since 2000	Associate, William Blair
Andrew T. Pfau, 1970	Secretary	Since 2009	Associate, William Blair
John M. Raczek, 1970	Assistant Treasurer	Since 2010	Associate, William Blair
Walter R. Randall, Jr., 1960	Chief Compliance Officer and Assistant Secretary	Since 2009	Associate, William Blair
Robert J. Toner, 1967	Assistant Secretary	Since 2016	Associate, William Blair (since 2015); formerly, Managing Director and Counsel, Wellington Management & Company LLP (2007-2015)

(1) The Trust’s officers, except the Chief Compliance Officer, are elected annually by the Board of Trustees. The Trust’s Chief Compliance Officer is designated by the Board of Trustees and may only be removed by action of the Board of Trustees, including a majority of independent trustees. Length of Time Served for all officers indicates the year the individual became an officer of the Trust.

The Statement of Additional Information for the William Blair Funds includes additional information about the trustees and is available without charge by calling 1-800-635-2886 (in Massachusetts 1-800-635-2840) or by writing the Fund.

196 Semiannual Report June 30, 2019

(Unaudited)

Proxy Voting

A description of the policies and procedures that the Funds use to determine how to vote proxies relating to portfolio securities and information regarding how the Funds voted proxies relating to portfolio securities for the most recent 12-month period ended December 31 are available without charge, upon request, by calling 1-800-635-2886 (in Massachusetts 1-800-635-2840), atwww.williamblairfunds.com and on the SEC’s website athttp://www.sec.gov.

Quarterly Portfolio Schedules

Each Fund files its complete schedule of portfolio holdings with the SEC for the first and third fiscal quarters of each fiscal year (quarters ended March 31 and September 30) on Form N-PORT. The Funds’ Forms N-PORT are available on the SEC’s website athttp://www.sec.gov.

Additional Federal Income Tax Information: (unaudited)

Under Section 852(b)(3)(C) of the Code, the Funds hereby designate the following amounts as capital gain dividends for the fiscal year ended December 31, 2018 (in thousands):

Fund	Capital Gain Dividend
Growth	$	78,680
Large Cap Growth		30,062
Mid Cap Growth		12,496
Small-Mid Cap Growth		224,256
Small-Mid Cap Value		451
Small Cap Growth		73,556
Small Cap Value		64,927
Global Leaders		27,739
International Leaders		12,780
International Developed Plus		695
International Growth		163,556
Institutional International Growth		166,380
International Small Cap Growth		38,842
Emerging Markets Leaders		17,246
Emerging Markets Growth		116,253
Emerging Markets Small Cap Growth		6,407

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Useful Information About Your Report (Unaudited)

Please refer to this information when reviewing the Expense Example for each Fund.

Expense Example

As a shareholder of a Fund, you incur two types of costs: (1) transaction costs and (2) ongoing costs, including management fees, distribution (12b-1) fees (for Class N shares except for the Institutional International Growth Fund and the Institutional International Developed Plus Fund) and other Fund expenses. The example is intended to help you understand your ongoing costs (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds. To do so, compare the Fund’s 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of other funds. The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire six-month period from January 1, 2019 to June 30, 2019.

Actual Expenses

In each example, the first line for each share class in the table provides information about theactualaccount values andactualexpenses. These expenses reflect the effect of any expense cap applicable to the share class during the period. Without this expense cap, the costs shown in the table would have been higher. You may use the information in this line, together with the amount you invested, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number in the first line under the heading entitled “Expenses Paid During the Period” to estimate the expenses you paid on your account during the period.

Hypothetical Example for Comparison Purposes

In each example, the second line for each share class in the table provides information abouthypotheticalaccount values andhypotheticalexpenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses. This is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate your actual ending account balance or the expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the Fund to the costs of investing in other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of other funds.

Please note that the expenses shown in both examples are meant to highlight your ongoing costs only and do not reflect any transactional costs or account type fees, such as IRA administration fees. These fees are discussed in the prospectus. Therefore, the second line of each share class in the table is useful in comparing ongoing costs only and will not help you determine the relative costs of owning different funds. In addition, if these transactional costs or account fees were included, your costs would have been higher.

198 Semiannual Report June 30, 2019

Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2019		Ending Account Value 06/30/2019		Expenses Paid During the Period (a)		Annualized Expense Ratio
Growth Fund
Class N-actual return	$	1,000.00	$	1,223.77	$	6.62		1.20	%
Class N-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Class I-actual return	$	1,000.00	$	1,225.95	$	5.13		0.93
Class I-hypothetical 5% return	$	1,000.00	$	1,045.39	$	4.72		0.93
Class R6-actual return (b)	$	1,000.00	$	1,025.32	$	1.45		0.87
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,045.69	$	4.41		0.87
Large Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,241.03	$	5.56		1.00
Class N-hypothetical 5% return	$	1,000.00	$	1,045.04	$	5.07		1.00
Class I-actual return	$	1,000.00	$	1,242.50	$	4.17		0.75
Class I-hypothetical 5% return	$	1,000.00	$	1,046.28	$	3.81		0.75
Class R6-actual return (b)	$	1,000.00	$	1,040.34	$	1.01		0.60
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,047.02	$	3.05		0.60
Mid Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,273.96	$	6.77		1.20
Class N-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Class I-actual return	$	1,000.00	$	1,274.35	$	5.36		0.95
Class I-hypothetical 5% return	$	1,000.00	$	1,045.29	$	4.82		0.95
Class R6-actual return (b)	$	1,000.00	$	1,020.12	$	1.49		0.90
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,045.54	$	4.56		0.90
Small-Mid Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,242.73	$	7.51		1.35
Class N-hypothetical 5% return	$	1,000.00	$	1,043.31	$	6.84		1.35
Class I-actual return	$	1,000.00	$	1,244.58	$	6.12		1.10
Class I-hypothetical 5% return	$	1,000.00	$	1,044.55	$	5.58		1.10
Class R6-actual return (b)	$	1,000.00	$	1,029.15	$	1.75		1.05
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,044.79	$	5.32		1.05
Small-Mid Cap Value Fund
Class N-actual return	$	1,000.00	$	1,166.67	$	6.72		1.25
Class N-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class I-actual return	$	1,000.00	$	1,167.93	$	5.38		1.00
Class I-hypothetical 5% return	$	1,000.00	$	1,045.04	$	5.07		1.00
Class R6-actual return (b)	$	1,000.00	$	987.19	$	1.55		0.95
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,045.29	$	4.82		0.95
Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,189.84	$	8.14		1.50
Class N-hypothetical 5% return	$	1,000.00	$	1,042.56	$	7.60		1.50
Class I-actual return	$	1,000.00	$	1,191.23	$	6.79		1.25
Class I-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class R6-actual return (b)	$	1,000.00	$	998.71	$	1.92		1.17
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,044.20	$	5.93		1.17
Small Cap Value Fund
Class N-actual return	$	1,000.00	$	1,162.23	$	8.04		1.50
Class N-hypothetical 5% return	$	1,000.00	$	1,042.56	$	7.60		1.50
Class I-actual return	$	1,000.00	$	1,163.87	$	6.71		1.25
Class I-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class R6-actual return (b)	$	1,000.00	$	992.30	$	1.92		1.17
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,044.20	$	5.93		1.17
Global Leaders Fund
Class N-actual return	$	1,000.00	$	1,206.63	$	6.84		1.25
Class N-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class I-actual return	$	1,000.00	$	1,209.24	$	5.48		1.00
Class I-hypothetical 5% return	$	1,000.00	$	1,045.04	$	5.07		1.00
Class R6-actual return	$	1,000.00	$	1,209.24	$	5.20		0.95
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.29	$	4.82		0.95

June 30, 2019 William Blair Funds 199

Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2019		Ending Account Value 06/30/2019		Expenses Paid During the Period (a)		Annualized Expense Ratio
International Leaders Fund
Class N-actual return	$	1,000.00	$	1,205.80	$	6.67		1.22	%
Class N-hypothetical 5% return	$	1,000.00	$	1,043.95	$	6.18		1.22
Class I-actual return	$	1,000.00	$	1,206.65	$	5.25		0.96
Class I-hypothetical 5% return	$	1,000.00	$	1,045.24	$	4.87		0.96
Class R6-actual return	$	1,000.00	$	1,207.52	$	4.98		0.91
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.49	$	4.62		0.91
International Developed Plus Fund (In Liquidation)
Class N-actual return	$	1,000.00	$	1,210.18	$	6.85		1.25
Class N-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class I-actual return	$	1,000.00	$	1,211.57	$	5.48		1.00
Class I-hypothetical 5% return	$	1,000.00	$	1,045.04	$	5.07		1.00
Institutional International Developed Plus Fund (In Liquidation)
Institutional-actual return	$	1,000.00	$	1,206.87	$	4.92		0.90
Institutional-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
International Growth Fund
Class N-actual return	$	1,000.00	$	1,192.71	$	7.88		1.45
Class N-hypothetical 5% return	$	1,000.00	$	1,042.81	$	7.34		1.45
Class I-actual return	$	1,000.00	$	1,194.40	$	6.26		1.15
Class I-hypothetical 5% return	$	1,000.00	$	1,044.30	$	5.83		1.15
Class R6-actual return (b)	$	1,000.00	$	1,021.04	$	1.79		1.08
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,044.64	$	5.48		1.08
Institutional International Growth Fund
Institutional-actual return	$	1,000.00	$	1,194.03	$	5.39		0.99
Institutional-hypothetical 5% return	$	1,000.00	$	1,045.09	$	5.02		0.99
International Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,187.26	$	8.13		1.50
Class N-hypothetical 5% return	$	1,000.00	$	1,042.56	$	7.60		1.50
Class I-actual return	$	1,000.00	$	1,189.47	$	6.73		1.24
Class I-hypothetical 5% return	$	1,000.00	$	1,043.85	$	6.28		1.24
Class R6-actual return	$	1,000.00	$	1,189.52	$	6.13		1.13
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.40	$	5.73		1.13
Emerging Markets Leaders Fund
Class N-actual return	$	1,000.00	$	1,167.07	$	8.06		1.50
Class N-hypothetical 5% return	$	1,000.00	$	1,042.56	$	7.60		1.50
Class I-actual return	$	1,000.00	$	1,169.29	$	6.72		1.25
Class I-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class R6-actual return	$	1,000.00	$	1,169.49	$	6.45		1.20
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Emerging Markets Growth Fund
Class N-actual return	$	1,000.00	$	1,157.99	$	8.13		1.52
Class N-hypothetical 5% return	$	1,000.00	$	1,042.46	$	7.70		1.52
Class I-actual return	$	1,000.00	$	1,159.11	$	6.80		1.27
Class I-hypothetical 5% return	$	1,000.00	$	1,043.70	$	6.44		1.27
Class R6-actual return	$	1,000.00	$	1,159.47	$	6.37		1.19
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.10	$	6.03		1.19
Emerging Markets Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,088.83	$	8.03		1.55
Class N-hypothetical 5% return	$	1,000.00	$	1,042.31	$	7.85		1.55
Class I-actual return	$	1,000.00	$	1,089.74	$	6.74		1.30
Class I-hypothetical 5% return	$	1,000.00	$	1,043.55	$	6.59		1.30
Class R6-actual return	$	1,000.00	$	1,090.33	$	6.48		1.25
Class R6-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25

200 Semiannual Report June 30, 2019

Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2019		Ending Account Value 06/30/2019			Expenses Paid During the Period (a)		Annualized Expense Ratio
Bond Fund
Class N-actual return	$	1,000.00	$	1,080.40		$	3.09		0.60	%
Class N-hypothetical 5% return	$	1,000.00	$	1,047.02		$	3.05		0.60
Class I-actual return	$	1,000.00	$	1,080.75		$	2.32		0.45
Class I-hypothetical 5% return	$	1,000.00	$	1,047.77		$	2.28		0.45
Class R6-actual return	$	1,000.00	$	1,081.09		$	2.06		0.40
Class R6-hypothetical 5% return	$	1,000.00	$	1,048.02		$	2.03		0.40
Income Fund
Class N-actual return	$	1,000.00	$	1,043.20		$	4.31		0.85
Class N-hypothetical 5% return	$	1,000.00	$	1,045.78		$	4.31		0.85
Class I-actual return	$	1,000.00	$	1,045.61		$	3.55		0.70
Class I-hypothetical 5% return	$	1,000.00	$	1,046.53		$	3.55		0.70
Class R6-actual return (b)	$	1,000.00	$	1,014.54		$	1.08		0.65
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,046.78		$	3.30		0.65
Low Duration Fund
Class N-actual return	$	1,000.00	$	1,024.42		$	2.76		0.55
Class N-hypothetical 5%	$	1,000.00	$	1,047.27		$	2.79		0.55
Class I-actual return	$	1,000.00	$	1,025.21		$	1.96		0.39
Class I-hypothetical 5%	$	1,000.00	$	1,048.07		$	1.98		0.39
Class R6-actual return	$	1,000.00	$	1,025.42		$	1.76		0.35
Class R6-hypothetical 5% return	$	1,000.00	$	1,048.26		$	1.78		0.35
Macro Allocation Fund
Class N-actual return	$	1,000.00	$	1,024.54		$	6.17		1.23
Class N-hypothetical 5%	$	1,000.00	$	1,043.90		$	6.23		1.23
Class I-actual return	$	1,000.00	$	1,026.36		$	4.92		0.98
Class I-hypothetical 5%	$	1,000.00	$	1,045.14	��	$	4.97		0.98
Class R6-actual return	$	1,000.00	$	1,026.36		$	4.52		0.90
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.54		$	4.56		0.90

(a)	Expenses are equal to the annualized expense ratio, multiplied by the average account value over the period, multiplied by the number of days in the period, 181 and divided by 365 (to reflect the one-half year period).
(b)	For the period May 2, 2019 (Commencement of Operations) to June 30, 2019.

June 30, 2019 William Blair Funds 201

BOARD OF TRUSTEES

Vann A. Avedisian

Principal, Highgate Holdings

Kathleen T. Barr

Retired Senior Managing Director, PNC Capital Advisors, LLC

Stephanie G. Braming, Chairman and President

Partner, William Blair

Daniel N. Leib

Chief Executive Officer, Donnelley Financial Solutions, Inc.

Dorri C. McWhorter

Chief Executive Officer, YWCA Metropolitan Chicago

Arthur J. Simon

Partner, William Blair

Thomas J. Skelly

Retired Managing Partner, Accenture

Steven R. Zenz

Retired Partner, KPMG LLP

Officers

Michael P. Balkin,Senior Vice President

Thomas Clarke,Senior Vice President

Daniel Crowe,Senior Vice President

Robert J. Duwa,Senior Vice President

Simon Fennell,Senior Vice President

Andrew G. Flynn,Senior Vice President

David C. Fording,Senior Vice President

James S. Golan,Senior Vice President

Chad M. Kilmer,Senior Vice President

Robert C. Lanphier, IV,Senior Vice President

Mark T. Leslie,Senior Vice President

Kenneth J. McAtamney,Senior Vice President

Todd M. McClone,Senior Vice President

David Merjan,Senior Vice President

David S. Mitchell,Senior Vice President

John C. Murphy,Senior Vice President

Casey K. Preyss,Senior Vice President

David P. Ricci,Senior Vice President

Ward D. Sexton,Senior Vice President

Brian D. Singer,Senior Vice President

Christopher T. Vincent,Senior Vice President

Dan Zelanzy,Senior Vice President

Lisa D. Rusch,Vice President

Paul J. Sularz,Vice President

Colette M. Garavalia,Treasurer

Andrew T. Pfau,Secretary

John M. Raczek,Assistant Treasurer

Walter R. Randall, Jr.,Chief Compliance Officer and Assistant Secretary

Robert J. Toner,Assistant Secretary

Investment Adviser

William Blair Investment Management, LLC

Distributor

William Blair & Company, L.L.C.

Independent Registered Public Accounting Firm

Ernst & Young LLP

Legal Counsel

Vedder Price P.C.

Transfer Agent

DST Asset Manager Solutions, Inc.

(formerly known as Boston Financial Data Services, Inc.)

For customer assistance, call 1-800-635-2886

P.O. Box 219137

Kansas City, Missouri 64121-9137

202 Semiannual Report June 30, 2019

William Blair Funds
U.S. EQUITY	GLOBAL EQUITY	FIXED INCOME
Growth Fund	Global Leaders Fund	Bond Fund
Large Cap Growth Fund		Income Fund
Mid Cap Growth Fund	INTERNATIONAL EQUITY	Low Duration Fund
Small-Mid Cap Growth Fund	International Leaders Fund
Small-Mid Cap Value Fund	International Developed Plus Fund	MULTI-ASSET AND
Small Cap Growth Fund	Institutional International Developed Plus Fund	ALTERNATIVE
Small Cap Value Fund	International Growth Fund	Macro Allocation Fund
	Institutional International Growth Fund
	International Small Cap Growth Fund
	Emerging Markets Leaders Fund
	Emerging Markets Growth Fund
	Emerging Markets Small Cap Growth Fund

		©	William Blair & Company, L.L.C., distributor
	+1 800 742 7272		150 North Riverside Plaza
	williamblairfunds.com		Chicago, Illinois 60606	00103188

Item 2. Code of Ethics

Not applicable to this filing.

Item 3. Audit Committee Financial Expert

Not applicable to this filing.

Item 4. Principal Accountant Fees and Services

Not applicable to this filing.

Item 5. Audit Committee of Listed Registrants

Not Applicable to this Registrant, insofar as the Registrant is not a listed company.

Item 6. Schedule of Investments

See Schedule of Investments in Item 1.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies

Not applicable to this Registrant, insofar as the Registrant is not a closed-end management investment company.

Item 8. Portfolio Managers of Closed Investment Companies

Not applicable to this Registrant, insofar as the Registrant is not a closed-end management investment company.

Item 9. Purchase of Equity Securities by Closed-End Management Investment Companies and Affiliated Purchasers

Not applicable to this Registrant, insofar as the Registrant is not a closed-end management investment company.

Item 10. Submission of Matters to a Vote of Security Holders

There have been no material changes to the procedures by which shareholders may recommend nominees to the Registrant’s Board of Trustees since the Registrant last provided disclosure in response to this item.

Item 11.

Controls and Procedures

(a) The Registrant’s principal executive and principal financial officer, or persons performing similar functions, have concluded that the Registrant’s Disclosure Controls and Procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the “1940 Act”) (17 CFR 270.30a-3(c)) are effective, as of a date within 90 days of the filing date of this report that includes the disclosure required by this paragraph, based on their evaluation of these controls and procedures required by Rule 30a-3 (b) under the 1940 Act (17 CFR 270.30a-3(b) and Rules 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)).

(b) There were no changes in the Registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act (17 CFR 270.30a-3(d)) that occurred during the final quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the Registrant’s internal control over financial reporting.

Item 12. Disclosure of Securities Lending Activities for Closed-End Management Investment Companies

Not applicable to this Registrant, insofar as the Registrant is not a closed-end management investment company.

Item 13. Exhibits

13. (a) (1) Code of Ethics

Not applicable to this filing.

13. (a) (2) (1)

Certification of Principal Executive Officer Required by Rule 30a-2(a) of the Investment Company Act is filed as an exhibit hereto.

13. (a) (2) (2)

Certification of Principal Financial Officer Required by Rule 30a-2(a) of the Investment Company Act is filed as an exhibit hereto.

13. (a) (3)

Not applicable to this Registrant.

13. (a) (4)

Not applicable to this filing.

13. (b)

Certifications of the Principal Executive Officer and Principal Financial Officer of the issuer as required by Rule 30a-2(b) of the Investment Company Act of 1940 are filed as exhibits hereto.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	William Blair Funds
	/s/ Stephanie G. Braming
By:	Stephanie G. Braming
	President (Principal Executive Officer)

Date: August 29, 2019

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the Registrant and in the capacities and on the dates indicated.

	/s/ Stephanie G. Braming
By:	Stephanie G. Braming
	President (Principal Executive Officer)

Date: August 29, 2019

	/s/ Colette M. Garavalia
By:	Colette M. Garavalia
	Treasurer (Principal Financial Officer)

Date: August 29, 2019