William Blair Funds NCSRS 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, 2021

Item 1. June 30, 2021 Semiannual Reports transmitted to shareholders.

				June 30, 2021


















	William Blair Funds
	Semiannual Report

Table of Contents


U.S. Growth Market Review and Outlook	3

U.S. Value Market Review and Outlook	4

Growth Fund
An Overview from the Portfolio Manager	5
Portfolio of Investments	7

Large Cap Growth Fund
An Overview from the Portfolio Managers	8
Portfolio of Investments	10

Mid Cap Growth Fund
An Overview from the Portfolio Managers	11
Portfolio of Investments	13

Small-Mid Cap Core Fund
An Overview from the Portfolio Managers	14
Portfolio of Investments	16

Small-Mid Cap Growth Fund
An Overview from the Portfolio Managers	18
Portfolio of Investments	20

Small Cap Growth Fund
An Overview from the Portfolio Managers	21
Portfolio of Investments	23

Small Cap Value Fund
An Overview from the Portfolio Managers	25
Portfolio of Investments	27

Global Markets Review and Outlook	29

Global Leaders Fund
An Overview from the Portfolio Managers	31
Portfolio of Investments	33

International Leaders Fund
An Overview from the Portfolio Managers	35
Portfolio of Investments	37

International Growth Fund
An Overview from the Portfolio Managers	39
Portfolio of Investments	41

Institutional International Growth Fund
An Overview from the Portfolio Managers	46
Portfolio of Investments	48

International Small Cap Growth Fund
An Overview from the Portfolio Managers	53
Portfolio of Investments	55

Emerging Markets Leaders Fund
An Overview from the Portfolio Managers	58
Portfolio of Investments	60

Emerging Markets Growth Fund
An Overview from the Portfolio Managers	62
Portfolio of Investments	64

June 30, 2021

William Blair Funds

Emerging Markets Small Cap Growth Fund
An Overview from the Portfolio Managers	67
Portfolio of Investments	69

Fixed Income Market Review and Outlook	72

Bond Fund
An Overview from the Portfolio Managers	73
Portfolio of Investments	75

Income Fund
An Overview from the Portfolio Manager	79
Portfolio of Investments	81

Low Duration Fund
An Overview from the Portfolio Managers	84
Portfolio of Investments	86

Emerging Markets Debt Market Review and Outlook	89

Emerging Markets Debt Fund
An Overview from the Portfolio Managers	90
Portfolio of Investments	93

Macro Allocation Fund
An Overview from the Portfolio Managers	98
Portfolio of Investments	101

Financial Statements	106

Notes to Financial Statements	124

Financial Highlights	145

Renewal of the Management Agreement	182

Approval of the Management Agreement for the William Blair Emerging Markets Debt Fund	186

Review of Liquidity Risk Management Program	187

Trustees and Officers	188

Fund Expenses	194

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.

Semiannual Report

June 30, 2021

U.S. Growth Market Review and Outlook

The U.S. equity market remained strong through the first half of 2021 as the U.S. economy continued to demonstrate improvement following disruption in 2020. First quarter market performance was supported by positive economic data, robust job growth and massive stimulus distributed to U.S. households and businesses. Improvements in corporate earnings growth also buoyed equities as corporations reported fourth quarter profits that broadly exceeded Wall Street’s expectations.

While the rate of COVID-19 vaccinations accelerated faster than anticipated across the country during the first quarter, the pace of vaccinations slowed through the second quarter despite an abundant supply of vaccines in the U.S. However, new cases of COVID-19, along with hospitalizations and deaths, significantly declined through the first half of the year, allowing the economy to recover as restrictions were eased across the country.

In the second quarter, manufacturing activity, gross domestic product (GDP), and job growth increased, further supporting the continued economic rebound. Notably, as U.S. employers increased hiring, the number of job openings outpaced the number of potential workers available to claim them, resulting in a sharp increase in wages. While the source of funding is yet to be determined, U.S. President Biden reached a bipartisan deal to boost infrastructure spending by $600 billion late in the second quarter. The Federal Open Market Committee (FOMC) reiterated its commitment to maintain a low target federal funds rate as the economy continues to recover. However, Federal Reserve policymakers announced that they expect an increase in the Federal funds rate by the end of 2023, an accelerated timeline relative to prior expectations. U.S. Treasury yields declined during the second quarter, facilitating a rotation that benefited growth-oriented segments of the market. With a largely positive fundamental backdrop and healthy corporate earnings reports, U.S. equity indices advanced in the second quarter.

Despite strong equity market performance and a continued sense of optimism around U.S. economic potential, some uncertainty remains surrounding the spread of new COVID-19 variants that have the potential to slow down the reopening of the economy. More specifically, the spread of the COVID-19 Delta variant coupled with vaccine hesitancy among some portions of the population may pose a challenge to the U.S. achieving herd immunity. While bolstering the economy, the surge in government spending and recovery in consumer spending activity has fueled inflation concerns among some investors, though the bond market does not appear to share those concerns, at least for the time being.

We continue to monitor economic developments and navigate through the business model implications of COVID-19 disruption and the subsequent economic recovery. Our focus remains on identifying companies with long-term durability, independent of the economic backdrop, whose stocks present compelling risk/reward opportunities. Through bottom-up, fundamental analysis, we seek to identify quality companies with superior management, high barriers to entry and differentiated products or services that we believe can outperform over a market cycle.

June 30, 2021

William Blair Funds

U.S. Value Market Review and Outlook

After a difficult 2020, we believe that the six month period ended June 30, 2021 has started on a positive note as we return to “normal”. Returns on the Russell 2000 Value index (the “Benchmark”) were robust in the first half of the year as COVID-19 vaccinations became more widely distributed and the country began to reopen.

As COVID-19 vaccines were rolled out, the U.S. went from virtually no fully vaccinated persons at the beginning of the year to roughly half the population fully vaccinated at the end of the second quarter. This has led to the economy reopening and has contributed to driving the unemployment rate down to under 6% after peaking near 15% in 2020. Gross domestic product has followed suit growing 6.4% in the first quarter, an acceleration from a 4.3% increase in the fourth quarter of 2020.

Most of the year-to-date return came in the first quarter with our Benchmark up over 21%, however, positive returns continued in the second quarter, advancing almost another 5%. Robust returns have been driven by COVID-19 vaccine distribution, strong macro data, positive earnings trends, and continued flowthrough of the benefits of government stimulus. All of these positives have overshadowed the risks of the continued spread of the Delta variant of COVID-19 globally.

Semiannual Report

June 30, 2021

	Growth Fund

	The Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGER

David C. Fording, CFA	The William Blair Growth Fund (Class N shares) (the “Fund”) posted a 13.09% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 3000^®Growth Index (the “Index”), increased 12.71%. Outperformance for the six month period was largely driven by stock selection. Selection in Health Care, including our position in Penumbra, and in Consumer Discretionary, including our positions in Revolve Group and Skyline Champion, benefited relative performance during the period. Shares of Penumbra, the market leader in mechanical stroke treatment, advanced on strong fundamental results. Online fashion retailer Revolve Group executed well through the COVID-19 pandemic and was a beneficiary of strong demand for refreshed wardrobes as the U.S. economy began to re-open. Other top contributors within the portfolio were Alphabet (Communication Services) and Cameco (Energy). In addition, not owning Apple (Information Technology) and Tesla (Consumer Discretionary), added to relative results. As it relates to Apple, our decision not to own the stock, due to the maturity of the high-end smart phone, tablet and PC markets, created a significant headwind to relative performance in 2020 given the revaluation of the company’s services business. This began to reverse during the first half of 2021. Top detractors from year-to-date performance included Rush Street Interactive (Consumer Discretionary), Ball Corp. (Materials), New Fortress Energy (Energy), and not owning Facebook (Communication Services). Rush Street Interactive, the largest U.S. online casino operator, was our top individual detractor. While the company had better than expected revenue, an acceleration of marketing spend resulted in earnings that were below expectations. Stock selection in Information Technology also dampened performance due in part to positions in Pure Storage and NICE, and not owning NVIDIA. While flash-based storage solutions provider Pure Storage reported strong results, the stock declined as valuations of longer-duration growth companies were pressured by rising interest rates early in the year. Fabless semiconductor company NVIDIA benefited from robust demand in gaming and datacenter; thus, not owning this strong performing stock resulted in a headwind to relative performance. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

June 30, 2021

William Blair Funds

Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		13.09	%		42.75	%		23.68	%		21.77	%		15.63	%		—	%
Class I		13.27			43.12			24.02			22.11			15.98			—
Class R6		13.31			43.22			—			—			—			28.23
Russell 3000^® Growth Index		12.71			42.99			24.47			23.31			17.54			29.78
S&P 500^®Index		15.25			40.79			18.67			17.65			14.84			21.22

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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, 2021. 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.

Semiannual Report

June 30, 2021

Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks
	Information Technology—38.9%
*	Adobe, Inc.		16,256	$	9,520
*	Advanced Micro Devices, Inc.		76,929		7,226
*	Alarm.com Holdings, Inc.		20,181		1,709
	Brooks Automation, Inc.		24,419		2,327
	Fidelity National Information Services, Inc.		50,903		7,211
*	GoDaddy, Inc.		57,097		4,965
*	Grid Dynamics Holdings, Inc.		184,373		2,771
	Mastercard, Inc.		37,958		13,858
	Microsoft Corporation		111,018		30,075
*	MongoDB, Inc.		7,635		2,760
	National Instruments Corporation		99,314		4,199
*	Nice, Ltd.—ADR		18,677		4,622
*	PayPal Holdings, Inc.		46,880		13,665
*	Pure Storage, Inc.		266,678		5,208
	Texas Instruments, Inc.		40,066		7,705
*	Verra Mobility Corporation		254,570		3,913
*	Workday, Inc.		22,601		5,396
					127,130
	Consumer Discretionary—14.8%
	Advance Auto Parts, Inc.		21,784		4,469
*	Amazon.com, Inc.		7,266		24,996
*	Bright Horizons Family Solutions, Inc.		29,148		4,288
*	Burlington Stores, Inc.		7,268		2,340
*	Etsy, Inc.		8,873		1,827
*	Revolve Group, Inc.		32,981		2,272
*	Rush Street Interactive, Inc.		212,743		2,608
*	Skyline Champion Corporation		44,925		2,395
*	Ulta Beauty, Inc.		9,111		3,150
					48,345
	Health Care—13.9%
*	Aerie Pharmaceuticals, Inc.		127,181		2,036
	Agilent Technologies, Inc.		34,083		5,038
*	Certara, Inc.		102,102		2,892
*	Exact Sciences Corporation		26,798		3,331
*	Horizon Therapeutics plc†		63,406		5,937
	STERIS plc†		24,653		5,086
	Stryker Corporation		32,168		8,355
	UnitedHealth Group, Inc.		22,342		8,947
	Zoetis, Inc.		20,115		3,749
					45,371
	Communication Services—11.1%
	Activision Blizzard, Inc.		47,891		4,571
*	Alphabet, Inc. Class “A”		10,549		25,758
	Warner Music Group Corporation		91,285		3,290
*	Zynga, Inc.		254,122		2,701
					36,320
	Industrials—8.7%
	BWX Technologies, Inc.		80,236		4,663
*	Copart, Inc.		47,217		6,225
*	CoStar Group, Inc.		46,470		3,849

	Issuer	Shares or Principal Amount		Value

	Common Stocks—(continued)
	Industrials—(continued)
	Fortive Corporation		60,892	$	4,246
*	Kornit Digital, Ltd.†		20,879		2,596
	The Brink’s Co.		60,922		4,681
*	Trex Co., Inc.		22,167		2,266
					28,526
	Consumer Staples—4.0%
	The Coca-Cola Co.		137,829		7,458
	The Estee Lauder Cos., Inc.		18,026		5,734
					13,192
	Financials—2.6%
	Aon plc†		18,555		4,430
	Ares Management Corporation		62,589		3,980
					8,410
	Energy—2.0%
	Cameco Corporation†		225,274		4,321
	New Fortress Energy, Inc.		54,935		2,081
					6,402
	Materials—1.4%
	Ball Corporation		54,789		4,439
	Real Estate—1.1%
	SBA Communications Corporation		10,837		3,454
	Total Common Stocks—98.5% (cost $164,351)				321,589

	*Repurchase Agreement*
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $5,019, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41,valued at $5,119		$5,019		5,019
	Total Repurchase Agreement—1.5% (cost $5,019)				5,019
	Total Investments—100.0% (cost $169,370)				326,608
	Liabilities, plus cash and other assets—(0.0)%				(141	)
	Net assets—100.0%			$	326,467

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Large Cap Growth Fund

	The Large Cap Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

James S. Golan, CFA David P. Ricci, CFA	The William Blair Large Cap Growth Fund (Class N shares) posted a 14.18% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 1000^®Growth Index (the “Index”), increased 12.99%. Outperformance for the six month period was largely the result of positive stock selection. Information Technology was a standout contributor due to our positions in Lam Research, Intuit and PayPal, as well as not owning Apple. Lam Research, a global supplier of wafer fabrication equipment and services, benefited from robust demand for semiconductor equipment and reported growth in its installed base and services business. As it relates to Apple, our decision not to own the stock, due to the maturity of the high-end smart phone, tablet and PC markets, created a significant headwind to relative performance in 2020 given the revaluation of the company’s services business. This began to reverse during the first half of 2021. Other top contributors were Alphabet (Communication Services), Apollo Global Management (Financials) and not owning Tesla (Consumer Discretionary). Alphabet Inc., an internet search engine company, had accelerating growth across its core segments, most notably in YouTube. Top detractors from relative performance during the period were NVIDIA (Information Technology), Guidewire (Information Technology), Fortive (Industrials), Mastercard (Information Technology) and ABIOMED (Health Care). We initiated a position in fabless semiconductor company NVIDIA during the second quarter. Strong performance of the stock, driven by robust demand in gaming and datacenter, both before and after our initial purchase, resulted in a headwind to relative performance. Guidewire, a software provider to the property & casualty insurance industry, delivered strong sales but increased cloud investments, given its transition to a cloud-based subscription model, which weighed on gross margins. Our decision to not own Facebook (Communication Services) also detracted from relative performance. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

Semiannual Report

June 30, 2021

Large Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		14.18	%		41.96	%		25.54	%		24.38	%		18.16	%		—	%
Class I		14.33			42.27			25.85			24.70			18.45			—
Class R6		14.34			42.31			—			—			—			30.66
Russell 1000^® Growth Index		12.99			42.50			25.14			23.66			17.87			30.23

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Large Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks
	Information Technology—45.4%
	Accenture plc†		88,800	$	26,177
*	Adobe, Inc.		46,410		27,180
*	Advanced Micro Devices, Inc.		268,098		25,182
	Fidelity National Information Services, Inc.		88,540		12,544
*	Guidewire Software, Inc.		86,680		9,771
	Intuit, Inc.		50,770		24,886
	Lam Research Corporation		36,920		24,024
	Mastercard, Inc.		104,180		38,035
	Microsoft Corporation		335,450		90,873
	NVIDIA Corporation		15,830		12,666
*	PayPal Holdings, Inc.		124,610		36,321
*	salesforce.com, Inc.		88,480		21,613
	Texas Instruments, Inc.		115,550		22,220
					371,492
	Consumer Discretionary—16.8%
*	Amazon.com, Inc.		21,365		73,499
*	Marriott International, Inc.		126,920		17,327
	NIKE, Inc.		169,610		26,203
	Starbucks Corporation		186,400		20,842
					137,871
	Communication Services—12.6%
	Activision Blizzard, Inc.		202,410		19,318
*	Alphabet, Inc. Class “A”		21,790		53,207
*	Alphabet, Inc. Class “C”		5,300		13,284
*	Live Nation Entertainment, Inc.		200,850		17,592
					103,401
	Health Care—9.6%
*	ABIOMED, Inc.		39,738		12,403
	Stryker Corporation		76,240		19,802
	UnitedHealth Group, Inc.		68,350		27,370
	Zoetis, Inc.		100,850		18,794
					78,369
	Industrials—6.4%
*	Copart, Inc.		153,580		20,246
	Equifax, Inc.		70,080		16,785
	Fortive Corporation		215,890		15,056
					52,087
	Consumer Staples—5.0%
	Costco Wholesale Corporation		56,070		22,185
	The Estee Lauder Cos., Inc.		58,970		18,757
					40,942
	Financials—2.0%
	Apollo Global Management, Inc.		260,930		16,230
	Materials—1.4%
	Linde plc†		38,720		11,194
	Total Common Stocks—99.2% (cost $511,330)				811,586


Issuer	Principal Amount		Value

*Repurchase Agreement*
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $6,451, collateralized by U.S. Treasury Bond, 1.875%,due 2/15/41, valued at $6,580		$6,451	$	6,451
Total Repurchase Agreement—0.8% (cost $6,451)				6,451
Total Investments—100.0% (cost $517,781)				818,037
Cash and other assets, less liabilities—0.0%				169
Net assets—100.0%			$	818,206

† = U.S. listed foreign security

* = Non-income producing security

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	Mid Cap Growth Fund

	The Mid Cap Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Daniel Crowe, CFA James E. Jones, CFA	The William Blair Mid Cap Growth Fund (Class N shares) (the “Fund”) posted a 3.57% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell Midcap^®Growth Index (the “Index”), increased 10.44%. In the six month period, the Fund lagged the Index, primarily due to stock-specific factors. Stock selection in Information Technology, including our positions in Anaplan, Pure Storage and RingCentral, and Industrials, including our position in CoStar, detracted from relative returns. Other top detractors included Take-Two Interactive Software (Communication Services), as well as not owning Moderna (Health Care). Shares of software company Anaplan declined as the company reported billings growth and revenue guidance below expectations. Concerns surrounding the strength of the gaming industry as we exit the COVID-19 pandemic weighed on software company Take-Two. Given our valuation sensitivity, we believe that normalization in valuations should prove to be beneficial to the relative performance of the Fund in the future. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

June 30, 2021

William Blair Funds

Mid Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year		10 Year			Since Inception(a)
Class N		3.57	%		33.14	%		16.49	%		16.58		11.52	%		—	%
Class I		3.61			33.36			16.77			16.86		11.80			—
Class R6		3.68			33.42			—			—		—			18.30
Russell Midcap^® Growth Index		10.44			43.77			22.39			20.52		15.13			25.72

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

Mid Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks
	Information Technology—30.5%
*	Anaplan, Inc.		23,480	$	1,251
*	Aspen Technology, Inc.		7,872		1,083
*	Cadence Design Systems, Inc.		20,450		2,798
	Dolby Laboratories, Inc.		11,715		1,151
*	Dynatrace, Inc.		35,905		2,098
*	EPAM Systems, Inc.		2,970		1,518
*	Euronet Worldwide, Inc.		13,755		1,862
*	GoDaddy, Inc.		17,805		1,548
*	Guidewire Software, Inc.		6,937		782
	Microchip Technology, Inc.		9,845		1,474
	MKS Instruments, Inc.		7,415		1,320
*	MongoDB, Inc.		4,915		1,777
*	Nice, Ltd.—ADR		6,620		1,638
	Pegasystems, Inc.		12,545		1,746
*	Pure Storage, Inc.		84,290		1,646
*	RingCentral, Inc.		4,810		1,398
*	Zendesk, Inc.		7,915		1,142
					26,232
	Health Care—21.1%
*	10X Genomics, Inc.		5,825		1,141
*	ABIOMED, Inc.		3,698		1,154
	Agilent Technologies, Inc.		14,635		2,163
*	Align Technology, Inc.		3,195		1,952
	Bio-Techne Corporation		2,742		1,235
*	Centene Corporation		12,105		883
*	Exact Sciences Corporation		10,000		1,243
*	Horizon Therapeutics plc†		28,340		2,654
*	IDEXX Laboratories, Inc.		2,390		1,509
*	Insulet Corporation		6,295		1,728
*	Mettler-Toledo International, Inc.		945		1,309
	STERIS plc†		5,450		1,124
					18,095
	Industrials—16.6%
*	Axon Enterprise, Inc.		7,525		1,330
	BWX Technologies, Inc.		35,744		2,077
*	Clarivate plc†		63,475		1,748
*	Copart, Inc.		23,567		3,107
*	CoStar Group, Inc.		29,790		2,467
	Equifax, Inc.		4,545		1,089
	Rockwell Automation, Inc.		4,025		1,151
*	Teledyne Technologies, Inc.		3,145		1,317
					14,286
	Consumer Discretionary—10.1%
	Advance Auto Parts, Inc.		6,873		1,410
*	Aptiv plc†		9,425		1,483
*	Bright Horizons Family Solutions, Inc.		14,010		2,061
*	Burlington Stores, Inc.		6,065		1,953
*	Etsy, Inc.		8,809		1,813
					8,720

	Issuer	Shares or Principal Amount		Value

	Common Stocks—(continued)
	Communication Services—6.0%
	Cable One, Inc.		305	$	583
*	Live Nation Entertainment, Inc.		11,029		966
*	Take-Two Interactive Software, Inc.		6,050		1,071
	Warner Music Group Corporation		41,770		1,505
*	Zillow Group, Inc.		8,645		1,057
					5,182
	Materials—5.4%
	Ball Corporation		17,665		1,431
	FMC Corporation		8,550		925
	Vulcan Materials Co.		13,365		2,327
					4,683
	Financials—4.2%
	Arthur J Gallagher & Co.		15,055		2,109
	East West Bancorp, Inc.		21,040		1,508
					3,617
	Consumer Staples—1.4%
*	BJ’s Wholesale Club Holdings, Inc.		24,399		1,161
	Real Estate—1.3%
	SBA Communications Corporation		3,365		1,073
	Energy—0.7%
	New Fortress Energy, Inc.		16,593		629
	Total Common Stocks—97.3% (cost $58,072)				83,678

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $3,224, collateralized by U.S. Treasury Bond, 1.875%,due 2/15/41, valued at $3,289		$3,224		3,224
	Total Repurchase Agreement—3.8% (cost $3,224)				3,224
	Total Investments—101.1% (cost $61,296)				86,902
	Liabilities, plus cash and other assets—(1.1)%				(924	)
	Net assets—100.0%			$	85,978

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Small-Mid Cap Core Fund

	The Small-Mid Cap Core Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Daniel Crowe, CFA Ward D. Sexton, CFA	The William Blair Small-Mid Cap Core Fund (Class I shares) posted a 18.32% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 2500™ Index (the “Index”), increased 16.97%. The Fund outperformed the Index in the six month period, primarily driven by stock-specific factors. Stock selection in Health Care, including our position in Owens & Minor, was a positive contributor to relative returns. Additionally, our typical underweight to speculative Biotechnology, which consists of companies without approved products, was a tailwind during the period. Other top contributors included Denbury (Energy) and Boot Barn Holdings (Consumer Discretionary), as well as Western Alliance Bancorp (Financials) and Stem (Industrials). Conversely, stock selection in Information Technology, including our positions in Vertex, NICE and Alarm.com, was a detractor during the period. Vertex, a provider of comprehensive tax solutions for businesses, lagged as slower growth among on-premise customers created a drag on the company’s overall revenue growth rate. Other laggards included New Fortress Energy (Energy) and BWX Technologies (Industrials). New Fortress Energy, an energy infrastructure company, reported lower-than-expected revenues and margins due to higher gas costs. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

Semiannual Report

June 30, 2021

Small-Mid Cap Core Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			Since Inception(a)
Class I		18.32	%		59.41	%		27.26	%
Class R6		18.40			59.36			27.31
Russell 2500^TMIndex		16.97			57.79			27.19


(a)	Since inception is for the period from October 1, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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 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^TMIndex measures the performance of those Russell 2500 companies with above average price-to-book ratios and forecasted growth rates.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Small-Mid Cap Core Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares			Value

	Common Stocks
	Industrials—18.9%
*	Axon Enterprise, Inc.		4,582	$	810
*	Builders FirstSource, Inc.		23,375		997
	BWX Technologies, Inc.		13,575		789
*	Casella Waste Systems, Inc.		4,261		270
	Douglas Dynamics, Inc.		7,603		309
*	Generac Holdings, Inc.		1,193		495
*	IAA, Inc.		5,301		289
*	Kornit Digital, Ltd.†		3,699		460
	Lincoln Electric Holdings, Inc.		4,451		586
	Luxfer Holdings plc†		34,516		768
*	Mercury Systems, Inc.		5,723		379
	Owens Corning		9,537		934
*	Stem, Inc.		15,292		551
	The Brink’s Co.		13,242		1,018
*	Trex Co., Inc.		5,503		563
*	WillScot Mobile Mini Holdings Corporation		14,222		396
					9,614
	Health Care—14.9%
*	Acadia Healthcare Co., Inc.		8,654		543
*	Certara, Inc.		16,936		480
*	Codexis, Inc.		26,354		597
	Encompass Health Corporation		6,614		516
*	Globus Medical, Inc.		4,905		380
*	Hanger, Inc.		23,686		599
*	HealthEquity, Inc.		4,379		352
*	Horizon Therapeutics plc†		6,997		655
*	LHC Group, Inc.		2,732		547
*	Ligand Pharmaceuticals, Inc.		2,003		263
*	Merit Medical Systems, Inc.		14,467		936
	Owens & Minor, Inc.		29,782		1,261
	STERIS plc†		2,340		483
					7,612
	Financials—14.6%
	Ares Management Corporation		10,795		686
	East West Bancorp, Inc.		14,681		1,053
*	Encore Capital Group, Inc.		8,265		392
	FirstCash, Inc.		3,785		289
	Glacier Bancorp, Inc.		12,690		699
	Hannon Armstrong Sustainable Infrastructure Capital, Inc.		5,776		324
	LPL Financial Holdings, Inc.		4,129		557
	PacWest Bancorp		11,153		459
	Virtu Financial, Inc.		19,950		551
	Voya Financial, Inc.		6,545		403
	Western Alliance Bancorp		13,319		1,237
	Wintrust Financial Corporation		10,291		778
					7,428
	Consumer Discretionary—12.1%
	Aramark		13,003		484
*	Boot Barn Holdings, Inc.		9,546		802
*	Bright Horizons Family Solutions, Inc.		3,436		505
*	Burlington Stores, Inc.		1,816		585
*	Callaway Golf Co.		13,541		457
*	Fox Factory Holding Corporation		3,787		590
*	Grand Canyon Education, Inc.		6,263		564
*	National Vision Holdings, Inc.		8,517		436



	Issuer	Shares			Value

	Common Stocks—(continued)
	Consumer Discretionary—(continued)
*	Skyline Champion Corporation		14,545	$	775
*	Terminix Global Holdings, Inc.		7,816		373
	Wyndham Hotels & Resorts, Inc.		8,513		615
					6,186
	Information Technology—10.8%
*	Alarm.com Holdings, Inc.		5,578		473
	Brooks Automation, Inc.		6,709		639
	CMC Materials, Inc.		2,094		316
*	Cree, Inc.		4,034		395
	Dolby Laboratories, Inc.		5,110		502
	Entegris, Inc.		3,213		395
*	Euronet Worldwide, Inc.		3,975		538
*	j2 Global, Inc.		3,332		458
*	Nice, Ltd.—ADR		2,501		619
*	Pure Storage, Inc.		22,288		435
*	Verra Mobility Corporation		47,711		734
					5,504
	Energy—7.2%
	Cameco Corporation†		47,979		920
*	Denbury, Inc.		22,942		1,762
*	Green Plains, Inc.		16,661		560
	New Fortress Energy, Inc.		11,591		439
					3,681
	Real Estate—6.4%
	Acadia Realty Trust		29,505		648
	Americold Realty Trust		11,585		438
	CoreSite Realty Corporation		4,156		559
	Equity LifeStyle Properties, Inc.		10,210		759
	Healthcare Realty Trust, Inc.		12,578		380
*	Sunstone Hotel Investors, Inc.		37,358		464
					3,248
	Materials—5.4%
	Crown Holdings, Inc.		7,899		808
	Eagle Materials, Inc.		4,532		644
	FMC Corporation		2,403		260
	Martin Marietta Materials, Inc.		1,421		500
*	Orion Engineered Carbons S.A.†		29,241		555
					2,767
	Consumer Staples—5.1%
*	BJ’s Wholesale Club Holdings, Inc.		9,844		469
	Inter Parfums, Inc.		6,641		478
*	Performance Food Group Co.		14,871		721
	Primo Water Corporation†		21,951		367
	Spectrum Brands Holdings, Inc.		6,483		551
					2,586
	Communication Services—2.2%
	Cable One, Inc.		193		369
*	Live Nation Entertainment, Inc.		4,060		356
*	Zynga, Inc.		36,969		393
					1,118
	Utilities—1.1%
	IDACORP, Inc.		5,920		577
	Total Common Stocks—98.7% (cost $38,668)				50,321

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Small-Mid Cap Core Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount			Value

Repurchase Agreement
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $761, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $777		$761	$	761
Total Repurchase Agreement—1.5% (cost $761)				761
Total Investments—100.2% (cost $39,429)				51,082
Liabilities, plus cash and other assets—(0.2)%				(123	)
Net assets—100.0%			$	50,959

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Small-Mid Cap Growth Fund

	The Small-Mid Cap Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Daniel Crowe, CFA James E. Jones, CFA	The William Blair Small-Mid Cap Growth Fund (Class N shares) (the “Fund”) posted an 8.04% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 2500™ Growth Index (the “Index”), increased 8.67%. The Fund performed in-line with the Index in the six month period, driven by a combination of style factors and stock-specific dynamics. From a style perspective, our bias toward companies with higher returns on invested capital and our underweight to the most expensive stocks in the Index were tailwinds as stocks with higher returns on invested capital and more attractive valuations generally outperformed during the period – a contrast to 2020. Partly offsetting this tailwind was our typical larger market cap profile relative to the Index as the smallest stocks in our universe outperformed. From a stock-specific standpoint, selection in Health Care, including our positions in Penumbra and Ligand Pharmaceuticals, was a standout contributor to relative returns. Penumbra, the market leader in mechanical stroke treatment, reported revenue results that exceeded expectations, led by strength in the peripheral vascular segment of the business and encouraging stability in the neuro segment. Additionally, our typical underweight to speculative Biotechnology, which consists of companies without approved products, was a tailwind during the period. Other top contributors included Generac Holdings (Industrials) and Axon Enterprise (Industrials), for the reasons outlined above, as well as Brooks Automation (Information Technology). Conversely, our top detractors during the period included Mercury Systems (Industrials), LiveRamp Holdings (Information Technology), NICE (Information Technology), Ritchie Bros Auctioneers (Industrials) and Pure Storage (Information Technology). Shares of Mercury Systems, a provider of sensor processing subsystems, were pressured, along with other defense-oriented companies, following the Democratic Senate victories in early January. Shares of technology company LiveRamp Holdings were pressured in the period as Google announced that it would cease the usage of cookies based on individuals’ web browsing history and shift to a cohort approach, which may inhibit LiveRamp’s and other industry participants’ ability to facilitate targeted advertising in the same way they have historically. Stock selection in Consumer Discretionary and Information Technology also detracted from relative returns. Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

Semiannual Report

June 30, 2021

Small-Mid Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		8.04	%		41.71	%		17.96	%		19.76	%		14.86	%		—	%
Class I		8.17			42.06			18.25			20.07			15.14			—
Class R6		8.19			42.13			—			—			—			22.44
Russell 2500^TM Growth Index		8.67			49.63			20.15			20.68			14.83			26.52

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Small-Mid Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares			Value

	Common Stocks
	Health Care—26.7%
*	10X Genomics, Inc.		241,959	$	47,380
*	ABIOMED, Inc.		168,372		52,551
*	Acadia Healthcare Co., Inc.		872,854		54,772
*	Amedisys, Inc.		168,112		41,176
	Bio-Techne Corporation		148,829		67,012
*	Blueprint Medicines Corporation		196,148		17,253
*	Certara, Inc.		659,106		18,673
*	Charles River Laboratories International, Inc.		180,586		66,802
	Encompass Health Corporation		849,082		66,254
*	Halozyme Therapeutics, Inc.		998,791		45,355
*	HealthEquity, Inc.		743,210		59,814
*	Horizon Therapeutics plc†		840,340		78,690
*	Insmed, Inc.		957,210		27,242
*	Inspire Medical Systems, Inc.		144,273		27,882
*	Insulet Corporation		160,232		43,985
*	Ligand Pharmaceuticals, Inc.		227,839		29,890
*	Masimo Corporation		99,086		24,023
*	Merit Medical Systems, Inc.		539,751		34,900
*	Penumbra, Inc.		158,547		43,451
	Teleflex, Inc.		78,369		31,488
*	Twist Bioscience Corporation		129,906		17,310
*	Veracyte, Inc.		811,474		32,443
					928,346
	Information Technology—24.9%
*	Alarm.com Holdings, Inc.		471,258		39,916
*	Aspen Technology, Inc.		325,833		44,815
*	Avalara, Inc.		289,090		46,775
	Brooks Automation, Inc.		700,830		66,775
*	Cree, Inc.		295,330		28,922
*	Dynatrace, Inc.		1,211,355		70,767
	Entegris, Inc.		323,976		39,839
*	Euronet Worldwide, Inc.		468,087		63,356
*	GoDaddy, Inc.		492,514		42,829
*	Guidewire Software, Inc.		380,153		42,851
*	j2 Global, Inc.		262,991		36,174
	National Instruments Corporation		905,848		38,299
*	Nice, Ltd.—ADR		227,468		56,289
*	Novanta, Inc.†		200,299		26,992
	Pegasystems, Inc.		259,495		36,119
*	Pure Storage, Inc.		2,675,368		52,250
*	Q2 Holdings, Inc.		196,178		20,124
*	Varonis Systems, Inc.		723,473		41,686
*	Workiva, Inc.		264,725		29,472
*	Zendesk, Inc.		290,659		41,954
					866,204
	Industrials—17.2%
*	Axon Enterprise, Inc.		385,080		68,082
*	Builders FirstSource, Inc.		1,546,217		65,962
	BWX Technologies, Inc.		1,297,270		75,397
*	Generac Holdings, Inc.		174,965		72,637
	HEICO Corporation		213,002		26,451
	Lincoln Electric Holdings, Inc.		207,617		27,345
*	Mercury Systems, Inc.		673,106		44,613
	Ritchie Bros Auctioneers, Inc.†		797,140		47,254
*	Stem, Inc.		876,012		31,545
	The Brink’s Co.		907,662		69,745
*	Trex Co., Inc.		659,954		67,454
	��				596,485

	Issuer	Shares or Principal Amount			Value

	Common Stocks—(continued)
	Consumer Discretionary—12.1%
*	Bright Horizons Family Solutions, Inc.		404,873	$	59,561
*	Burlington Stores, Inc.		134,902		43,437
*	Fox Factory Holding Corporation		343,210		53,424
*	Grand Canyon Education, Inc.		410,485		36,931
*	Helen of Troy, Ltd.†		175,412		40,015
*	Leslie’s, Inc.		1,342,088		36,894
*	National Vision Holdings, Inc.		696,237		35,599
*	Revolve Group, Inc.		448,711		30,916
*	Terminix Global Holdings, Inc.		766,029		36,547
	Wyndham Hotels & Resorts, Inc.		642,445		46,443
					419,767
	Materials—4.2%
	Crown Holdings, Inc.		718,277		73,415
	Martin Marietta Materials, Inc.		210,736		74,139
					147,554
	Financials—4.1%
	Ares Management Corporation		631,948		40,186
	FirstCash, Inc.		321,643		24,586
	Virtu Financial, Inc.		1,454,330		40,183
	Western Alliance Bancorp		401,676		37,296
					142,251
	Communication Services—3.7%
	Cable One, Inc.		22,181		42,428
*	Live Nation Entertainment, Inc.		466,644		40,874
*	Zynga, Inc.		4,157,975		44,199
					127,501
	Energy—3.3%
	Cameco Corporation†		2,557,201		49,047
*	Denbury, Inc.		569,874		43,755
	New Fortress Energy, Inc.		622,854		23,594
					116,396
	Consumer Staples—1.5%
*	BJ’s Wholesale Club Holdings, Inc.		540,598		25,721
*	Celsius Holdings, Inc.		360,057		27,397
					53,118
	Real Estate—1.0%
	FirstService Corporation†		199,605		34,184
	Total Common Stocks—98.7% (cost $2,351,508)				3,431,806

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $11,036, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $11,257		$11,036		11,036
	Total Repurchase Agreement—0.3% (cost $11,036)				11,036
	Total Investments—99.0% (cost $2,362,544)				3,442,842
	Cash and other assets, less liabilities—1.0%				35,417
	Net assets—100.0%			$	3,478,259

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	Small Cap Growth Fund

	The Small Cap Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Ward D. Sexton, CFA Mark C. Thompson, CFA	The William Blair Small Cap Growth Fund (Class N shares) posted an 12.84% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 2000^®Growth Index (the “Index”), increased 8.98%. Outperformance for the six month period was due to a combination of style dynamics and stock-specific factors. From a style perspective, our smaller market cap bias and our typical underweight to the most expensive stocks in the Index were tailwinds as the least expensive and smaller market capitalization companies in the Index outperformed. From a stock-specific standpoint, selection was positive across several sectors, most notably Health Care, including our position in Ligand Pharmaceuticals and our typical underweight to Biotechnology. Other top contributors were Consumer Discretionary holdings Revolve Group and Boot Barn Holdings. Online fashion retailer Revolve Group and western and work wear retailer Boot Barn executed well through the COVID-19 pandemic and, despite appealing to different demographics, were both beneficiaries of strong demand for refreshed wardrobes as the U.S. economy began to re-open. Other standout performers included Denbury (Energy) and Stem Inc. (Industrials). Stock selection in Information Technology, including our position in LiveRamp Holdings, detracted from relative performance. LiveRamp lagged as Google announced that it would cease the usage of cookies based on individuals’ web browsing history and shift to a cohort approach, which may inhibit LiveRamp’s and other industry participants’ ability to facilitate targeted advertising in the same way they have historically. Rush Street Interactive, the largest U.S. online casino operator, was our top individual detractor.While the company had better than expected revenue, an acceleration of marketing spend resulted in earnings that were below expectations. Other notable laggards included Amicus Therapeutics (Health Care), Mercury Systems (Industrials) and QuinStreet (Communication Services). Please refer to the U.S. Growth Market Review and Outlook relating to the Fund on page 3.

June 30, 2021

William Blair Funds

Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		12.84	%		60.72	%		17.40	%		22.04	%		15.59	%		—	%
Class I		13.01			61.11			17.69			22.34			15.88			—
Class R6		13.05			61.26			—			—			—			24.67
Russell 2000^® Growth Index		8.98			51.36			15.94			18.76			13.52			23.48

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares			Value

	Common Stocks
	Health Care—25.4%
*	Acadia Healthcare Co., Inc.		184,489	$	11,577
*	Aerie Pharmaceuticals, Inc.		563,111		9,015
*	Amicus Therapeutics, Inc.		578,590		5,578
*	AxoGen, Inc.		417,040		9,012
*	Blueprint Medicines Corporation		52,970		4,659
*	Butterfly Network, Inc.		297,189		4,303
*	CareDx, Inc.		98,597		9,024
*	Certara, Inc.		320,584		9,082
*	Codexis, Inc.		409,638		9,282
*	CryoLife, Inc.		271,152		7,701
*	Halozyme Therapeutics, Inc.		155,700		7,070
*	Hanger, Inc.		432,170		10,925
*	Health Catalyst, Inc.		232,578		12,910
*	HealthEquity, Inc.		99,095		7,975
*	Innovage Holding Corporation		330,850		7,050
*	Insmed, Inc.		251,690		7,163
*	Inspire Medical Systems, Inc.		38,650		7,470
*	LHC Group, Inc.		47,913		9,595
*	Ligand Pharmaceuticals, Inc.		54,728		7,180
*	Merit Medical Systems, Inc.		175,300		11,335
*	Twist Bioscience Corporation		41,056		5,471
	US Physical Therapy, Inc.		53,147		6,158
*	Veracyte, Inc.		148,090		5,921
*	Vericel Corporation		67,900		3,565
					189,021
	Industrials—23.5%
	Albany International Corporation		102,435		9,143
*	Builders FirstSource, Inc.		275,770		11,764
	BWX Technologies, Inc.		234,129		13,608
*	Casella Waste Systems, Inc.		187,600		11,900
	Douglas Dynamics, Inc.		170,063		6,920
*	Ducommun, Inc.		264,009		14,404
*	Energy Recovery, Inc.		369,016		8,406
*	Forrester Research, Inc.		146,739		6,721
*	IAA, Inc.		100,970		5,507
*	Kornit Digital, Ltd.†		60,870		7,568
	Lincoln Electric Holdings, Inc.		50,920		6,707
	Luxfer Holdings plc†		482,306		10,731
*	Mercury Systems, Inc.		94,996		6,296
*	Montrose Environmental Group, Inc.		221,568		11,889
*	PAE, Inc.		997,208		8,875
	Ritchie Bros Auctioneers, Inc.†		143,695		8,518
*	Stem, Inc.		262,194		9,442
	The Brink’s Co.		208,516		16,023
					174,422
	Information Technology—22.8%
*	Alarm.com Holdings, Inc.		96,870		8,205
	American Software, Inc.		271,000		5,951
	Brooks Automation, Inc.		139,515		13,293
*	BTRS Holdings, Inc.		343,880		4,340
	CMC Materials, Inc.		50,150		7,560
	Computer Services, Inc.		110,659		6,225
*	Euronet Worldwide, Inc.		59,700		8,080
*	Grid Dynamics Holdings, Inc.		820,795		12,337



	Issuer	Shares			Value

	Common Stocks—(continued)
	Information Technology—(continued)
*	j2 Global, Inc.		85,483	$	11,758
	Littelfuse, Inc.		14,063		3,583
*	LivePerson, Inc.		141,397		8,942
*	LiveRamp Holdings, Inc.		154,520		7,239
*	Novanta, Inc.†		38,630		5,206
*	PAR Technology Corporation		30,350		2,123
*	PDF Solutions, Inc.		217,182		3,948
*	PROS Holdings, Inc.		189,070		8,616
*	Pure Storage, Inc.		474,656		9,270
*	SiTime Corporation		40,625		5,143
*	Upland Software, Inc.		174,130		7,169
*	Varonis Systems, Inc.		138,630		7,988
*	Verra Mobility Corporation		713,949		10,973
*	Vertex, Inc.		201,519		4,421
*	WNS Holdings, Ltd.—ADR		92,092		7,355
					169,725
	Consumer Discretionary—9.2%
*	Boot Barn Holdings, Inc.		147,094		12,363
*	Dine Brands Global, Inc.		56,780		5,068
*	National Vision Holdings, Inc.		159,788		8,170
*	Porch Group, Inc.		357,518		6,914
*	Revolve Group, Inc.		184,647		12,722
*	Rush Street Interactive, Inc.		464,450		5,694
*	Skyline Champion Corporation		219,790		11,715
	Winmark Corporation		28,100		5,398
					68,044
	Financials—4.3%
*	Encore Capital Group, Inc.		148,353		7,030
	FirstCash, Inc.		125,832		9,619
	Home BancShares, Inc.		329,828		8,140
*	Open Lending Corporation		172,167		7,419
					32,208
	Energy—4.3%
	Cameco Corporation†		685,120		13,141
*	Denbury, Inc.		147,559		11,329
*	Green Plains, Inc.		224,680		7,554
					32,024
	Consumer Staples—2.8%
*	BJ’s Wholesale Club Holdings, Inc.		149,550		7,115
*	The Beauty Health Co.		510,400		8,575
*	Vital Farms, Inc.		234,460		4,680
					20,370
	Communication Services—2.2%
*	Gogo, Inc.		636,260		7,240
*	QuinStreet, Inc.		505,165		9,386
					16,626
	Real Estate—2.2%
	Colliers International Group, Inc.†		68,568		7,678
	FirstService Corporation†		51,357		8,796
					16,474

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

	Issuer	Shares or Principal Amount			Value

	Common Stocks—(continued)
	Materials—1.3%
*	Orion Engineered Carbons S.A.†		520,997	$	9,894
	Total Common Stocks—98.0% (cost $503,164)				728,808

	Exchange-Traded Funds
	Exchange-Traded Fund—1.0%
	iShares Russell 2000 Growth ETF		24,370		7,596
	Total Exchange-Traded Fund—1.0% (cost $7,303)				7,596

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $3,521, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $3,591	$	3,521		3,521
	Total Repurchase Agreement—0.5% (cost $3,521)				3,521
	Total Investments—99.5% (cost $513,988)				739,925
	Cash and other assets, less liabilities—0.5%				3,874
	Net assets—100.0%			$	743,799

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	Small Cap Value Fund

	The Small Cap Value Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Mark T. Leslie, CFA Stephen Livingston, CFA David S. Mitchell, CFA	The William Blair Small Cap Value Fund (Class N shares) (the “Fund”) posted a 17.64% increase, net of fees, for six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Russell 2000^®Value Index (the “Index”), increased 26.69%. The Fund’s relative performance was impacted by the combination of stock selection and style headwinds during the period given its larger market capitalization and higher quality biases. During the first half of 2021 there was significant performance dispersion across the size and quality spectrum as smaller capitalizations and lower quality stocks dramatically outperformed. At the sector level, Consumer Discretionary was the largest detractor during the period due to lack of exposure to Specialty Retail broadly, but also not owning GameStop, which resulted in 91 basis points (bps) of underperformance in the period. Within Communication Services, lack of exposure to Entertainment, particularly AMC Entertainment, resulted in 137 basis points of underperformance in the period. The relative return in Industrials was driven by stock selection in Commercial Services & Supplies, Aerospace & Defense, Building Products, and Machinery. The relative outperformance in Financials was driven by strong stock selection in Regional Banks. Looking specifically at stock selection, the strategy’s largest detractors during the period were AMC Entertainment (Communication Services), GameStop (Consumer Discretionary), and LiveRamp Holdings (Information Technology). Offsetting these detractors were our investments in PDC Energy (Energy), Western Alliance Bank (Financials), and Boston Private Financial (Financials). Please refer to the U.S. Value Market Review and Outlook relating to the Fund on page 4.

The portfolio managers have changed due to the Fund’s reorganization effective July 16, 2021. Refer to Note 8—Subsequent Events for further details of the reorganization.

June 30, 2021

William Blair Funds

Small Cap Value Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		17.64	%		50.57	%		3.45	%		7.30	%		7.85	%		—	%
Class I		17.83			51.06			3.72			7.56			8.12			—
Class R6		17.85			50.97			—			—			—			6.37
Russell 2000^® Value Index		26.69			73.28			10.27			13.62			10.85			17.13

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

Small Cap Value Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks
	Financials—27.9%
	Banc of California, Inc.		18,678	$	328
	Banner Corporation		8,849		480
	Boston Private Financial Holdings, Inc.		27,047		399
	Cadence BanCorp		26,841		560
	CNO Financial Group, Inc.		26,324		622
	First American Financial Corporation		7,356		459
	FNB Corporation		46,979		579
	Glacier Bancorp, Inc.		12,239		674
	Hancock Whitney Corporation		20,799		924
	Home BancShares, Inc.		31,877		787
	Horace Mann Educators Corporation		11,426		427
	National Bank Holdings Corporation		13,470		508
	OceanFirst Financial Corporation		19,449		405
	PacWest Bancorp		17,079		703
	Radian Group, Inc.		32,724		728
	Renasant Corporation		13,147		526
	Sandy Spring Bancorp, Inc.		13,642		602
	Seacoast Banking Corporation of Florida		19,522		667
	Selective Insurance Group, Inc.		10,705		869
	The Hanover Insurance Group, Inc.		4,695		637
	Umpqua Holdings Corporation		32,891		607
	Western Alliance Bancorp		10,883		1,010
					13,501
	Industrials—16.4%
	Alamo Group, Inc.		1,405		214
	Brady Corporation		17,644		989
*	Chart Industries, Inc.		5,010		733
	Curtiss-Wright Corporation		6,323		751
	ESCO Technologies, Inc.		4,035		379
	Federal Signal Corporation		8,696		350
*	FTI Consulting, Inc.		4,610		630
*	Gibraltar Industries, Inc.		9,900		755
	Rexnord Corporation		10,530		527
*	Saia, Inc.		2,294		481
	Simpson Manufacturing Co., Inc.		4,817		532
	UniFirst Corporation		2,945		691
	Watts Water Technologies, Inc.		6,094		889
					7,921
	Consumer Discretionary—11.2%
	Carter’s, Inc.		5,507		568
*	Cavco Industries, Inc.		1,502		334
	Churchill Downs, Inc.		2,500		496
*	Deckers Outdoor Corporation		2,471		949
*	Helen of Troy, Ltd.†		2,992		683
	KB Home		9,565		389
*	Monarch Casino & Resort, Inc.		9,718		643
	Murphy USA, Inc.		4,390		585
*	TopBuild Corporation		3,881		768
					5,415
	Real Estate—8.3%
	Acadia Realty Trust		14,070		309
	Agree Realty Corporation		7,693		542
	American Assets Trust, Inc.		14,769		551
	CoreSite Realty Corporation		2,356		317
	Healthcare Realty Trust, Inc.		18,651		563



	Issuer	Shares		Value

	Common Stocks—(continued)
	Real Estate—(continued)
	Highwoods Properties, Inc.		12,070	$	545
	Life Storage, Inc.		5,987		643
	Terreno Realty Corporation		8,200		529
					3,999
	Health Care—6.3%
*	Allscripts Healthcare Solutions, Inc.		16,975		314
*	Avanos Medical, Inc.		8,110		295
	CONMED Corporation		6,502		894
	Encompass Health Corporation		9,923		774
*	Integer Holdings Corporation		8,291		781
					3,058
	Materials—5.9%
	Avient Corporation		12,682		624
	Carpenter Technology Corporation		12,065		485
	Minerals Technologies, Inc.		7,885		620
	Sensient Technologies Corporation		6,242		540
	Silgan Holdings, Inc.		13,857		575
					2,844
	Information Technology—5.8%
	Belden, Inc.		9,825		497
*	j2 Global, Inc.		4,421		608
*	LiveRamp Holdings, Inc.		7,197		337
	MAXIMUS, Inc.		5,974		525
*	Semtech Corporation		2,800		193
*	Viavi Solutions, Inc.		35,559		628
					2,788
	Energy—5.6%
	Archrock, Inc.		43,973		392
	Brigham Minerals, Inc.		24,589		523
	Cactus, Inc.		7,287		268
*	CNX Resources Corporation		36,682		501
	HollyFrontier Corporation		8,044		265
	PDC Energy, Inc.		16,922		775
					2,724
	Consumer Staples—4.6%
*	BJ’s Wholesale Club Holdings, Inc.		7,643		364
	Casey’s General Stores, Inc.		2,692		524
*	Darling Ingredients, Inc.		11,701		790
	J&J Snack Foods Corporation		3,148		549
					2,227
	Utilities—4.1%
	Black Hills Corporation		8,057		529
	Chesapeake Utilities Corporation		3,865		465
	IDACORP, Inc.		4,738		462
	ONE Gas, Inc.		7,469		553
					2,009
	Communication Services—2.2%
	John Wiley & Sons, Inc.		6,380		384
	Nexstar Media Group, Inc.		2,395		354
*	QuinStreet, Inc.		16,348		304
					1,042
	Total Common Stocks—98.3% (cost $30,861)				47,528

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Small Cap Value Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


	Principal
Issuer	Amount		Value

Common Stocks—(continued)
Repurchase Agreement
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $932, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $950		$932	$	932
Total Repurchase Agreement—1.9% (cost $932)				932
Total Investments—100.2% (cost $31,793)				48,460
Liabilities, plus cash and other assets—(0.2)%				(81	)
Net assets—100.0%			$	48,379

* = Non-income producing security

† = U.S. listed foreign security

The composition of the portfolio of investments has changed due to the Fund’s reorganization effective July 16, 2021. Refer to Note 8—Subsequent Events for further details of the reorganization.

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Global Markets Review and Outlook

Global equities continued to advance in the second quarter (the MSCI All Country World IMI Index (the “Index”) gained +7.18% in the second quarter and 12.68% year-to-date through June 30, 2021 in USD terms) amid further success of COVID-19 vaccination rollouts and a healthy rebound in economic activity, especially in developed markets. The sharp style rotation in the first quarter which favored value areas subsided in the second quarter with growth stocks outperforming. From a global sector perspective, Information Technology outperformed (+10.22% for the quarter and +12.39% year-to-date) while Utilities significantly underperformed (-0.09% for the quarter and +0.86% year-to-date). Energy also continued to rally (+10.08% for the quarter and +30.51% year-to-date) as rising demand drove stronger crude oil prices.

US equities advanced (+8.36% for the quarter and +15.05% year-to-date) as investors welcomed news of additional federal spending to revive the economy. In addition to the $1.9 trillion COVID-19 relief plan and $2.3 trillion infrastructure plan introduced in the first quarter, President Biden’s Administration also announced a $1.8 trillion American Families Plan emphasizing strong support for national childcare to ensure an equitable recovery from the COVID-19 pandemic, especially for female workers and mothers. Significant federal spending drove concerns over rising inflation. In May, headline inflation rose to 5.0% year on year, above expectations.

European equities kept pace with the Index (+7.26% for the quarter and +11.81% year-to-date) as several European countries gradually relaxed restrictions on travel and business activity. Economic data was also supportive, specifically the Eurozone manufacturing purchasing manager’s index (PMI) which rose to a record high level (63.4) in June.

Strength within Latin America (+15.56% for the quarter and +9.64% year-to-date) was primarily driven by Brazil (+23.60% for the quarter and +11.89% year-to-date) bolstered by stronger commodity prices and currency tailwinds. China underperformed on a relative basis (+2.35% for the quarter and +2.36% year-to-date) amid concerns over tightening liquidity and increased regulatory oversight on large capitalization technology companies.

In our view, the market is experiencing a tug of war between the impressive acceleration of economic growth due to global re-openings, and fears of a resurgence of COVID-19 case counts. We believe economic growth will win out. While concerning, the positive view is that the COVID-19 vaccines appear to be working, and the COVID-19 Delta variant is proving so far not as harmful.

As for recent economic activity, it has been more of the same, with both consumption and production activity strong – in some cases above 2019 levels. While we expect a sequential peak in gross domestic product (GDP) growth likely occurred in the second quarter, we also expect the remainder of the year should continue to be quite strong.

We believe that corporate earnings growth, which has been impressive thus far in 2021, remains underestimated. In fact, projected bottom-up corporate profit growth lags top-down GDP estimates by a wider margin than we saw coming out of the global financial crisis of 2008 (“GFC”). Thus, we are confident profit growth will continue to surprise to the upside.

As is the case in almost every economic expansion period, earnings growth has been the key market driver. We believe we are now clearly in expansion mode, with the corporate profit picture and market leadership following the script.

During the second quarter, we saw earnings revisions and momentum lead market performance, while valuation flipped from dominating in the first quarter (typical of recovery periods) to not much of a factor. Quality and Growth re-asserted themselves positively. All of these characteristics are very typical of performance during an economic expansion and we believe they are likely to continue.

Inflation concerns have been a natural topic of debate all year. We continue to foresee reflation back to long-term, i.e., manageable, levels. In this unique cycle, we are experiencing price increases driven by the re-opening of supply not keeping up with demand fast enough. While in some cases we are already seeing a few industrial commodity prices reverting, we expect that it will take another three-to-six months for the supply catch up to occur across most industries.

The global market, as measured by the MSCI All Country World IMI, is up close to 40% over the last twelve months. While market valuations receive a lot of attention, perhaps unnoticed is that this market appreciation has been driven entirely by earnings growth. The market valuation has actually somewhat come down during this period.

June 30, 2021

William Blair Funds

Global Markets Review and Outlook (continued)

The valuation multiple of more economically sensitive sectors of the market (e.g., cyclicals and financials) have increased along with a resurgence of their growth. In contrast, companies with stronger structural long-term growth have lagged on a relative basis, and in some cases have seen their stock multiples compress. We view this is a classic period of structural winners “growing into” their multiples.

Consistent with our growth outlook we believe most of this experience is likely behind us but may occur off and on during the balance of the year while the market digests the economic and profit picture. Ultimately as economic growth reverts to the long-term mean and the market begins to discount peak cyclical earnings, the structural growers will again have their day.

Corporate profit margins and cash flows have been impressive, and we believe we are entering an era where more of that cash flow is likely to be directed to capital investment and research and development.

We see two reasons for rapidly ramping capital spending by corporates: 1) digitalization of businesses is now a survival imperative; and 2) shortening supply chains has become necessary to improve operational resilience.

We are witnessing it already: After the GFC, it took US private sector investment (excluding housing) nearly four years to recover to pre-crisis levels. By contrast, capital expenditures in the first quarter of 2021 already surpassed the fourth quarter of 2019 peak. Intellectual property and software investment recovered by the fourth quarter of 2020, compared to six quarters post-GFC.

We believe the COVID-19 pandemic has elevated operational efficiencies of digital business models into a survival imperative for virtually all companies. Digital businesses generally were able to operate relatively unscathed during the COVID-19 pandemic lockdowns, while more traditional, high physical contact businesses were more likely to be forced to shut down. Within industries, those companies who had proactively employed more data and digitally-enabled business practices pressed their competitive advantage. We are seeing companies of all sizes accelerate their investment into cloud-based systems, remote work, digitally driven customer service solutions, and the requisite software applications.

Companies have spent decades rationalizing their supply chains with the goal of maximum operational efficiency. Such extreme efficiency comes with high potential fragility. And we believe this fragility was fully exposed by COVID-19-related lockdowns and associated export restrictions. Companies are looking to shore up their supply chains, in some instances by reducing or duplicating some parts of the chain. Some of this was starting to happen in response to chilling economic relations between the U.S. and China prior to the COVID-19 pandemic. COVID-19 has only added more reasons to accelerate the buildout.

In our view, shifts in the geopolitical environment in which corporates operate also support investment rather than cash preservation. Since the early 1980s everything from taxation to antitrust to regulatory and labor policies was geared to improving corporate profitability. Today, there is growing recognition that these policies may have gone too far. The operating environment is changing on the margin: pressure for stronger wage growth, especially at the bottom of the income distribution is rising.

The Group of Seven (G7) agreeing on a minimum corporate tax rate suggests that the race to the bottom is over. Antitrust authorities in China, Europe and the U.S. are openly exploring ways to bring competition standards to industries and businesses that have been able to behave as monopolies or quasi monopolies. These changes incentivize corporate investment, which in turn will likely expand supply and enable stronger economic growth without higher inflation. We will have more to say on this topic in the coming months and quarters.

Semiannual Report

June 30, 2021

	Global Leaders Fund

	The Global Leaders Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Andrew G. Flynn, CFA Kenneth J. McAtamney Hugo Scott-Gall	The William Blair Global Leaders Fund (Class N shares) (the “Fund”) posted a 10.80% increase, net of fees, for six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI All Country World IMI (net) (the “Index”), increased 12.68%. Six-month underperformance versus the Index was primarily driven by weaker stock selection within Industrials, as Nihon M&A Center Inc detracted. Nihon M&A is a high-quality Japanese growth company that provides advisory services to small and medium-sized businesses facing succession-oriented challenges, which is common given Japan’s aging demographics. It is led by an entrepreneurial management team that has built an attractive network of national relationships aimed at identifying buyers and sellers and sourcing transactions. Management recently noted that with the second stage of lockdowns related to COVID-19 in Japan, deal times could extend. While this has weighed on near-term expectations, our long-term outlook remains unchanged as the company continues to benefit from structural tailwinds. We believe it is the dominant player in the market due to its extensive network and continued strong execution should continue to result in steady deal flow, attractive margins, and expanding returns. Partially offsetting these effects was positive stock selection within the Consumer Discretionary and Health Care sectors. Within Consumer Discretionary, Aristocrat Leisure drove outperformance. Aristocrat Leisure is a leading content and equipment supplier in the global slot machine market, with an expanding share in the higher-margin revenue-sharing segment thanks to strong performance of innovative products. Digital has been a new growth driver for Aristocrat, with in-house games and M&A steadily expanding the addressable market beyond land-based casinos for sustainable longer-term growth. The company is recovering faster than market expectations where revenues have normalized close to pre-COVID levels. Within Health Care sector, Charles River Laboratories contributed to relative results. Charles River is a contract research organization (CRO) that has evolved to be the global leader in the early stage portion of the research market with a dominant market share lead, working on 85% of all FDA-approved drugs in both 2018 and 2019. In our view, the company has several key competitive advantages that support its market-leading position including a global network, strong brand reputation, and broad product/service portfolio. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

June 30, 2021

William Blair Funds

Global Leaders Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		10.80	%		42.55	%		18.27	%		18.59	%		12.19	%		—	%
Class I		10.93			42.92			18.57			18.91			12.50			—
Class R6		10.99			42.96			18.63			18.98			—			13.94
MSCI ACW IMI (net)		12.68			40.94			14.24			14.55			9.90			11.31

(a)	Since inception is for the period from December 19, 2012 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

Global Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks
	Western Hemisphere—49.8%
	Canada—1.3%
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		4,961	$	1,811
	United States—48.5%
*	Adobe, Inc. (Software)		3,173		1,858
*	Align Technology, Inc. (Health care equipment & supplies)		2,227		1,361
*	Alphabet, Inc. Class “A” (Interactive Media & Services)		1,713		4,183
*	Amazon.com, Inc. (Internet & direct marketing retail)		1,115		3,836
	BlackRock, Inc. (Capital markets)		2,288		2,002
*	Charles River Laboratories International, Inc. (Life sciences tools & services)		6,701		2,479
*	CoStar Group, Inc. (Professional services)		14,870		1,231
	Ecolab, Inc. (Chemicals)		5,452		1,123
*	Edwards Lifesciences Corporation (Health care equipment & supplies)		15,213		1,576
*	Facebook, Inc. Class “A” (Interactive Media & Services)		10,162		3,533
	Fidelity National Information Services, Inc. (IT services)		12,022		1,703
*	IDEXX Laboratories, Inc. (Health care equipment & supplies)		3,155		1,992
	Intercontinental Exchange, Inc. (Capital markets)		14,765		1,752
*	Intuitive Surgical, Inc. (Health care equipment & supplies)		1,638		1,506
	Lockheed Martin Corporation (Aerospace & defense)		5,753		2,177
	Mastercard, Inc. Class “A” (IT services)		9,411		3,436
	Microsoft Corporation (Software)		14,599		3,955
	NextEra Energy, Inc. (Electric utilities)		14,592		1,069
	NIKE, Inc. Class “B” (Textiles, apparel & luxury goods)		14,142		2,185
*	PayPal Holdings, Inc. (IT services)		8,992		2,621
	Prologis, Inc. (Equity REIT)		11,032		1,319
	Roper Technologies, Inc. (Industrial conglomerates)		3,394		1,596
*	salesforce.com, Inc. (Software)		12,239		2,990
	The Estee Lauder Cos., Inc. Class “A” (Personal products)		7,035		2,238
	Thermo Fisher Scientific, Inc. (Life sciences tools & services)		3,853		1,944
*	Ulta Beauty, Inc. (Specialty retail)		7,706		2,664
	Union Pacific Corporation (Road & rail)		9,699		2,133
	UnitedHealth Group, Inc. (Health care providers & services)		5,564		2,228
*	Veeva Systems, Inc. Class “A” (Health care technology)		2,998		932
*	Workday, Inc. Class “A” (Software)		7,876		1,880
	Zoetis, Inc. (Pharmaceuticals)		9,846		1,835
					67,337



	Issuer	Shares		Value

	Common Stocks—(continued)

	Europe—25.3%
	Denmark—3.6%
	Chr Hansen Holding A/S (Chemicals)		10,259	$	926
	DSV PANALPINA A/S (Air freight & logistics)		9,956		2,322
	Novo Nordisk A/S Class “B” (Pharmaceuticals)		21,057		1,764
					5,012
	France—4.2%
*	Airbus SE (Aerospace & defense)		27,279		3,508
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		2,963		2,323
					5,831
	Germany—4.4%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		76,506		3,068
	MTU Aero Engines AG (Aerospace & defense)		8,793		2,178
	Rational AG (Machinery)		883		800
					6,046
	Ireland—3.6%
	Allegion plc (Building products)†		7,618		1,061
*	Aptiv plc (Auto components)†		15,672		2,466
*	Ryanair Holdings plc—ADR (Airlines)		13,789		1,492
					5,019
	Netherlands—1.0%
*	Adyen N.V. (IT services)		581		1,420
	Sweden—5.2%
	Atlas Copco AB Class “A” (Machinery)		40,061		2,453
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		5,210		823
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		194,885		2,887
	Indutrade AB (Machinery)		41,640		1,066
					7,229
	Switzerland—3.3%
	Lonza Group AG (Life sciences tools & services)		2,776		1,968
	Partners Group Holding AG (Capital markets)		1,695		2,567
					4,535

	Emerging Asia—8.1%
	China—4.4%
*	Alibaba Group Holding, Ltd. (Internet & direct marketing retail)		90,344		2,560
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		48,300		1,220
	Tencent Holdings, Ltd. (Interactive Media & Services)		30,400		2,286
					6,066

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Global Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	India—1.4%
*	HDFC Bank, Ltd.—ADR (Banks)		27,882	$	2,039
	Taiwan—2.3%
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		26,620		3,199

	Asia—5.6%
	Australia—3.7%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		77,246		2,496
*	Atlassian Corporation plc Class “A” (Software)†		4,924		1,265
	CSL, Ltd. (Biotechnology)		6,350		1,358
					5,119
	Hong Kong—1.5%
	AIA Group, Ltd. (Insurance)		167,400		2,081
	New Zealand—0.4%
	Fisher & Paykel Healthcare Corp., Ltd. (Health care equipment & supplies)		23,878		519

	Japan—4.6%
	Daikin Industries, Ltd. (Building products)		9,600		1,788
	Keyence Corporation (Electronic equipment, instruments & components)		3,400		1,716
	Nihon M&A Center, Inc. (Professional services)		57,400		1,489
	SMC Corporation (Machinery)		2,400		1,418
					6,411

	United Kingdom—3.5%
*	Compass Group plc (Hotels, restaurants & leisure)		118,703		2,499
	Experian plc (Professional services)		27,176		1,047
	Halma plc (Electronic equipment, instruments & components)		15,487		577
	Rentokil Initial plc (Commercial services & supplies)		114,974		787
					4,910

	Emerging Latin America—1.6%
	Argentina—1.6%
*	Globant S.A. (IT services)†		5,695		1,248
*	MercadoLibre, Inc. (Internet & direct marketing retail)		590		920
					2,168
	Total Common Stocks—98.5% (cost $71,771)				136,752


	Principal
Issuer	Amount		Value

Common Stocks—(continued)
Repurchase Agreement
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $1,591, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $1,623		$1,591	$	1,591
Total Repurchase Agreement—1.2% (cost $1,591)				1,591
Total Investments—99.7% (cost $73,362)				138,343
Cash and other assets, less liabilities—0.3%				485
Net assets—100.0%			$	138,828

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Information Technology	24.7	%
Industrials	20.9	%
Consumer Discretionary	18.9	%
Health Care	15.7	%
Financials	7.6	%
Communication Services	7.3	%
Consumer Staples	1.6	%
Materials	1.5	%
Real Estate	1.0	%
Utilities	0.8	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

U.S. Dollar	60.6	%
Euro	9.7	%
Hong Kong Dollar	5.9	%
Swedish Krona	5.3	%
Japanese Yen	4.7	%
Danish Krone	3.7	%
British Pound Sterling	3.6	%
Swiss Franc	3.3	%
Australian Dollar	2.8	%
All Other Currencies	0.4	%
Total	100.0	%

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	International Leaders Fund

	The International Leaders Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Simon Fennell Kenneth J. McAtamney Alaina Anderson, CFA	The William Blair International Leaders Fund (Class N shares) (the “Fund”) posted a 6.21% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI (net) (the “Index”), increased 9.58%. Six-month underperformance versus the Index was primarily driven by negative stock selection across most sectors. The Consumer Discretionary, Energy and Information Technology sectors had the largest impact on relative returns. Within Consumer Discretionary, TAL Education Group hampered relative performance as the company declined amid regulatory headwinds as the Chinese government seeks to enhance standards of after school education and tutoring and reduce the tutoring burden for children. Neste, a producer of renewable diesel within the Energy sector, hurt relative results. Neste is the world’s largest producer of renewable diesel and jet fuel refined from waste and residues. We believe that Neste offers a superior product compared to petroleum diesel as it not only helps meet renewable/carbon reduction targets, but also burns cleaner in internal combustion engines, resulting in lower emissions and engine maintenance cost. The COVID-19 pandemic is anticipated to have a negative impact on demand this year, but we expect it will have limited impact on longer-term growth. Within the Information Technology sector Keyence hindered relative returns as the company’s share price adjusted lower after strong performance in 2020. Keyence develops and manufactures sensors and measuring instruments used for factory automation. We believe fundamentals in factory automation are inflecting sharply higher as demand recovers against year-over-year comparisons. We continue to see Keyence as well positioned to drive innovation that will expand its total addressable market and enhance an already attractive growth opportunity. Partially offsetting these effects was positive stock selection within the Communication Services and Health Care sectors. Within Communication Services, Sea helped relative performance. Sea is a South East Asian mobile gaming and e-commerce company that primarily operates in seven South East Asian markets, including Indonesia, Malaysia, the Philippines, Singapore, Thailand, Taiwan and Vietnam. More recently, it has expanded its gaming operations to include India, Russia and Latin America. The company is the market leader in both gaming revenues and e-commerce, and current game success coupled with a robust pipeline are driving higher revenue growth and profitability expectations, and e-commerce operating metrics continue to be strong. Straumann, the global market leader in esthetic dentistry within Health Care, was an additional source of outperformance. The company develops, manufactures, and supplies dental implants, instruments, biomaterials, CADCAM prosthetics, digital equipment, software, and clear aligners for applications in replacement, restorative, and orthodontic dentistry. We believe that Straumann is more than just a products company. As a total solution provider, it offers training, support, and a wide range of services to dental practitioners, clinics, and laboratories all over the world. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

June 30, 2021

William Blair Funds

International Leaders Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		6.21	%		36.04	%		15.12	%		15.38	%		11.71	%
Class I(a)		6.32			36.36			15.41			15.68			11.98
MSCI ACW Ex-U.S. IMI (net)(a)		9.58			37.18			9.42			11.20			7.79
Class R6(b)		6.36			36.46			15.48			15.78			12.10
MSCI ACW Ex-U.S. IMI (net)(b)		9.58			37.18			9.42			11.20			7.52

(a)	Since inception is for the period from August 16, 2012 (Commencement of Operations) to June 30, 2021.
(b)	Since inception is for the period from November 2, 2012 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

International Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	*Common Stocks*

	*Europe, Mid-East—50.8%*
	Denmark—6.5%
	Chr Hansen Holding A/S (Chemicals)		103,186	$	9,313
	Coloplast A/S Class “B” (Health care equipment & supplies)		103,985		17,062
	DSV PANALPINA A/S (Air freight & logistics)		74,473		17,368
	Novo Nordisk A/S Class “B” (Pharmaceuticals)		249,651		20,915
	Orsted A/S (Electric utilities)		88,167		12,372
					77,030
	Finland—1.4%
	Neste Oyj (Oil, gas & consumable fuels)		275,306		16,858
	France—13.0%
*	Airbus SE (Aerospace & defense)		274,493		35,295
	L’Oreal S.A. (Personal products)		43,360		19,322
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		57,056		44,740
	Safran S.A. (Aerospace & defense)		200,969		27,862
	Sartorius Stedim Biotech (Life sciences tools & services)		32,834		15,530
	Teleperformance (Professional services)		32,020		12,996
					155,745
	Germany—4.3%
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		629,573		25,247
	Rational AG (Machinery)		16,364		14,825
*	TeamViewer AG (Software)		310,830		11,691
					51,763
	Ireland—3.2%
*	ICON plc (Life sciences tools & services)†		19,745		4,081
	Kingspan Group plc (Building products)		219,393		20,718
*	Ryanair Holdings plc—ADR (Airlines)		123,638		13,379
					38,178
	Israel—0.2%
*	Wix.com, Ltd. (IT services)†		9,075		2,634
	Netherlands—4.3%
*	Adyen N.V. (IT services)		9,296		22,712
	ASML Holding N.V. (Semiconductors & semiconductor equipment)		41,348		28,407
					51,119
	Norway—1.0%
	TOMRA Systems ASA (Commercial services & supplies)		218,942		12,078
	Spain—1.8%
*	Amadeus IT Group S.A. (IT services)		309,705		21,784
	Sweden—5.6%
	Atlas Copco AB Class “A” (Machinery)		404,322		24,756
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		1,781,914		26,402
	Nibe Industrier AB Class “B” (Building products)		1,501,613		15,795
					66,953



	Issuer	Shares		Value

	*Common Stocks—(continued)*

	*Europe, Mid-East—(continued)*
	Switzerland—9.5%
	Lonza Group AG (Life sciences tools & services)		38,228	$	27,095
	Partners Group Holding AG (Capital markets)		15,769		23,886
	Sika AG (Chemicals)		51,459		16,824
	Straumann Holding AG (Health care equipment & supplies)		19,958		31,816
	Temenos AG (Software)		88,178		14,162
					113,783

	*Emerging Asia—17.0%*
	China—9.3%
*	Alibaba Group Holding, Ltd. (Internet & direct marketing retail)		958,156		27,149
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		489,572		9,770
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		43,500		13,846
	NetEase, Inc. (Entertainment)		966,575		21,898
*	TAL Education Group—ADR (Diversified consumer services)		284,804		7,186
	Tencent Holdings, Ltd. (Interactive Media & Services)		371,100		27,913
*	Wuxi Biologics Cayman, Inc. (Life sciences tools & services)		177,000		3,244
					111,006
	India—3.9%
	Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		643,514		21,451
	Reliance Industries, Ltd. (Oil, gas & consumable fuels)		919,740		25,763
					47,214
	Taiwan—2.7%
	Taiwan Semiconductor Manufacturing Co., Ltd. (Semiconductors & semiconductor equipment)		1,511,000		32,267
	Thailand—1.1%
*	Sea, Ltd.—ADR (Entertainment)		48,657		13,361

	*United Kingdom—12.0%*
	Ashtead Group plc (Trading companies & distributors)		369,321		27,404
*	Compass Group plc (Hotels, restaurants & leisure)		669,961		14,105
	Experian plc (Professional services)		511,214		19,702
	Halma plc (Electronic equipment, instruments & components)		311,514		11,600
	London Stock Exchange Group plc (Capital markets)		187,833		20,708
	Rentokil Initial plc (Commercial services & supplies)		1,651,799		11,311
	Segro plc (Equity REIT)		1,113,285		16,855
	Spirax-Sarco Engineering plc (Machinery)		75,042		14,133
*	Trainline plc (Hotels, restaurants & leisure)		1,810,907		7,355
					143,173

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

International Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

	Issuer	Shares or Principal Amount		Value

	*Common Stocks—(continued)*

	Japan—8.4%
	Asahi Intecc Co., Ltd. (Health care equipment & supplies)		228,200	$	5,456
	Daikin Industries, Ltd. (Building products)		99,100		18,456
	Hoya Corporation (Health care equipment & supplies)		146,700		19,451
	Keyence Corporation (Electronic equipment, instruments & components)		46,400		23,418
	M3, Inc. (Health care technology)		90,700		6,623
	Nihon M&A Center, Inc. (Professional services)		379,300		9,836
	SMC Corporation (Machinery)		29,600		17,492
					100,732

	Asia—6.1%
	Australia—3.6%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		706,296		22,824
*	Atlassian Corporation plc Class “A” (Software)†		41,505		10,661
	CSL, Ltd. (Biotechnology)		45,082		9,642
					43,127
	Hong Kong—1.8%
	AIA Group, Ltd. (Insurance)		1,744,400		21,681
	New Zealand—0.7%
	Fisher & Paykel Healthcare Corp., Ltd. (Health care equipment & supplies)		384,906		8,373

	Canada—3.1%
	Canadian National Railway Co. (Road & rail)		221,612		23,382
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		38,125		13,915
					37,297

	Emerging Latin America—1.2%
	Argentina—1.2%
*	MercadoLibre, Inc. (Internet & direct marketing retail)		8,984		13,995
	Total Common Stocks—98.6% (cost $808,230)				1,180,151

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $16,293, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $16,619		$16,293		16,293
	Total Repurchase Agreement—1.4% (cost $16,293)				16,293
	Total Investments—100.0% (cost $824,523)				1,196,444
	Liabilities, plus cash and other assets—(0.0)%				(191	)
	Net assets—100.0%			$	1,196,253

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	28.7	%
Information Technology	19.6	%
Health Care	14.3	%
Consumer Discretionary	12.8	%
Financials	7.4	%
Communication Services	5.4	%
Consumer Staples	3.6	%
Energy	3.6	%
Materials	2.2	%
Real Estate	1.4	%
Utilities	1.0	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	27.0	%
British Pound Sterling	12.1	%
Swiss Franc	9.7	%
Hong Kong Dollar	8.6	%
Japanese Yen	8.5	%
U.S. Dollar	6.7	%
Danish Krone	6.5	%
Swedish Krona	5.7	%
Indian Rupee	4.0	%
Australian Dollar	2.8	%
New Taiwan Dollar	2.7	%
Chinese Yuan Renminbi	2.0	%
Canadian Dollar	2.0	%
Norwegian Krone	1.0	%
All Other Currencies	0.7	%
Total	100.0	%

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	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 8.28% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI (net) (the “Index”), increased 9.58%. Six-month underperformance versus the Index was primarily driven by negative stock selection across most sectors. Stock selection within the Financials sector was particularly weak, as Ping An Insurance and Bank Central Asia weighed on relative performance in the period. Ping An is the largest insurance company by market cap globally and the leading life insurance in what we expect will be the largest market (by size and growth) for life insurance over the next decade. Although Ping An remains firmly in the expanding growth phase of its corporate lifecycle, its breadth of services propels it into a different category and closer to becoming a dominant technology-powered retail financial services group. It has developed a broad ecosystem comprising over 6oo million internet users and over 220 million retail customers. Ping An continues to improve its cross-sell of products from other parts of the group, which increases income without incurring the cost of acquiring new clients. While recent results have been below average due to COVID-19, we believe it will revert to its previous growth trajectory as the economy recovers. Partially offsetting these effects was positive stock selection within the Health Care and Communication Services sectors. Within Health Care, Wuxi Biologics and Lonza added to relative returns. Wuxi Biologics is a contract development and manufacturing organization (CDMO) that offers a full range of research and manufacturing services for biologic drugs. The services are designed to help clients improve research and development efficiency, shorten development timelines and lower costs. Importantly, Wuxi is the only company offering comprehensive CDMO services for biologics in China. As a result, Wuxi is the domestic market leader with approximately 50% market share. Supporting Wuxi’s growth profile is strong demand for biologics outsourcing services worldwide. We believe Wuxi’s strong execution and favorable market dynamics will generate strong earnings growth for the foreseeable future. Lonza is a leader in custom manufacturing of biopharmaceuticals and specialty ingredients. Lonza offers highly visible growth and given the strong market demand for outsourced biopharma production and related services, we remain confident it can deliver on growth in the future. Within Communication Services, Kakao boosted relative returns. Kakao is a South Korean online platform. It operates KakaoTalk, the largest mobile messaging app, and Daum, the second largest web portal. Other businesses include ride-hailing, music streaming, and financial services businesses with Kakao Pay and Kakao Bank. We believe Kakao will sustain its position as one of the most dominant tech companies in South Korea, given the strong market position, management execution, business development, and potential to drive synergies and capture sustained value around its various platform, content, and new businesses. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

June 30, 2021

William Blair Funds

International Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		8.28	%		42.17	%		15.73	%		14.69	%		8.52	%		—	%
Class I		8.45			42.58			16.09			15.04			8.85			—
Class R6		8.47			42.70			—			—			—			24.31
MSCI ACW Ex-U.S. IMI (net)		9.58			37.18			9.42			11.20			5.65			13.16

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	*Europe, Mid-East—45.4%*
	Belgium—0.3%
	Warehouses De Pauw CVA (Equity REIT)		167,727	$	6,404
	Denmark—4.1%
	Chr Hansen Holding A/S (Chemicals)		67,200		6,065
	Coloplast A/S Class “B” (Health care equipment & supplies)		58,540		9,605
	DSV PANALPINA A/S (Air freight & logistics)		180,021		41,982
*	Genmab A/S (Biotechnology)		36,970		15,127
	Netcompany Group A/S (Software)		51,304		5,829
	Orsted A/S (Electric utilities)		84,520		11,860
	Royal Unibrew A/S (Beverages)		38,877		4,952
					95,420
	Finland—0.9%
	Neste Oyj (Oil, gas & consumable fuels)		353,022		21,616
	France—10.5%
*	Airbus SE (Aerospace & defense)		308,528		39,671
	Dassault Systemes SE (Software)		77,298		18,744
	Hermes International (Textiles, apparel & luxury goods)		8,077		11,766
	Kering S.A. (Textiles, apparel & luxury goods)		36,217		31,650
	L’Oreal S.A. (Personal products)		54,069		24,093
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		49,760		39,018
	Safran S.A. (Aerospace & defense)		189,420		26,261
	Sartorius Stedim Biotech (Life sciences tools & services)		34,021		16,092
	Teleperformance (Professional services)		72,200		29,305
*	Worldline S.A. (IT services)		99,633		9,326
					245,926
	Germany—5.9%
	Carl Zeiss Meditec AG (Health care equipment & supplies)		55,353		10,695
	CompuGroup Medical SE & Co. KgaA (Health care technology)		58,310		4,567
*	CTS Eventim AG & Co. KGaA (Entertainment)		95,342		5,958
*	HelloFresh SE (Internet & direct marketing retail)		139,023		13,514
*	Hypoport SE (Diversified financial services)		6,469		3,344
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		583,628		23,405
	KION Group AG (Machinery)		85,145		9,074
	MTU Aero Engines AG (Aerospace & defense)		123,966		30,707
	Nemetschek SE (Software)		49,522		3,789
	Puma SE (Textiles, apparel & luxury goods)		148,357		17,688
*	TeamViewer AG (Software)		100,753		3,789
	Vonovia SE (Real estate management & development)		186,284		12,043
					138,573



	Issuer	Shares		Value

	Common Stocks—(continued)

	*Europe, Mid-East—(continued)*
	Ireland—2.1%
*	ICON plc (Life sciences tools & services)†		80,305	$	16,600
	Kingspan Group plc (Building products)		177,389		16,751
*	Ryanair Holdings plc—ADR (Airlines)		150,477		16,283
					49,634
	Israel—1.0%
*	Inmode, Ltd. (Health care equipment & supplies)†		51,530		4,879
*	Nice, Ltd.—ADR (Software)		19,868		4,917
*	Wix.com, Ltd. (IT services)†		46,977		13,636
					23,432
	Italy—0.7%
	Amplifon SpA (Health care providers & services)		125,920		6,217
*	Brunello Cucinelli SpA (Textiles, apparel & luxury goods)		74,032		4,330
	Moncler SpA (Textiles, apparel & luxury goods)		90,292		6,109
					16,656
	Luxembourg—0.9%
*	Eurofins Scientific SE (Life sciences tools & services)		138,968		15,885
	Tenaris S.A. (Energy equipment & services)		485,810		5,295
					21,180
	Netherlands—3.7%
*	Adyen N.V. (IT services)		10,296		25,156
	ASML Holding N.V. (Semiconductors & semiconductor equipment)		67,210		46,175
	BE Semiconductor Industries N.V. (Semiconductors & semiconductor equipment)		44,902		3,809
	Euronext N.V. (Capital markets)		56,115		6,102
	IMCD N.V. (Trading companies & distributors)		39,422		6,268
					87,510
	Norway—0.7%
*	Pexip Holding ASA (Software)		270,767		2,418
	Scatec ASA (Independent power & renewable electricity producers)		132,851		3,518
	TOMRA Systems ASA (Commercial services & supplies)		177,930		9,816
					15,752
	Spain—1.6%
*	Amadeus IT Group S.A. (IT services)		399,224		28,081
	EDP Renovaveis S.A. (Independent power & renewable electricity producers)		356,629		8,263
*	Solaria Energia y Medio Ambiente S.A. (Independent power & renewable electricity producers)		139,739		2,525
					38,869

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	*Europe, Mid-East—(continued)*
	Sweden—6.1%
	AddTech AB Class “B” (Trading companies & distributors)		221,990	$	3,683
	Atlas Copco AB Class “A” (Machinery)		643,938		39,428
	Beijer Ref AB (Trading companies & distributors)		327,187		5,830
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		121,729		19,236
	Hexagon AB Class “B” (Electronic equipment, instruments & components)		1,782,817		26,415
	Indutrade AB (Machinery)		354,824		9,080
	Investment AB Latour Class “B” (Industrial conglomerates)		217,844		7,148
	Lifco AB Class “B” (Industrial conglomerates)		281,605		6,581
	Nibe Industrier AB Class “B” (Building products)		881,586		9,273
	Nolato AB Class “B” (Industrial conglomerates)		489,162		4,813
	Sweco AB Class “B” (Construction & engineering)		220,842		4,018
	Thule Group AB (Leisure products)		98,345		4,360
	Vitrolife AB (Biotechnology)		90,663		3,767
					143,632
	Switzerland—6.9%
	Belimo Holding AG (Building products)		9,327		4,264
	Logitech International S.A. (Technology hardware, storage & peripherals)		42,659		5,168
	Lonza Group AG (Life sciences tools & services)		40,841		28,947
	Partners Group Holding AG (Capital markets)		18,433		27,921
	Siegfried Holding AG (Life sciences tools & services)		6,047		5,670
*	SIG Combibloc Group AG (Containers & packaging)		277,302		7,535
	Sika AG (Chemicals)		106,091		34,685
*	Softwareone Holding AG (Electronic equipment, instruments & components)		137,061		3,237
	Straumann Holding AG (Health care equipment & supplies)		12,701		20,247
	Tecan Group AG (Life sciences tools & services)		12,736		6,310
	Temenos AG (Software)		44,952		7,220
	VAT Group AG (Machinery)		23,473		7,804
*	Zur Rose Group AG (Food & staples retailing)		9,415		3,607
					162,615

	*Emerging Asia—23.3%*
	China—12.9%
	A-Living Smart City Services Co., Ltd. (Commercial services & supplies)		1,194,250		5,945
	Aier Eye Hospital Group Co., Ltd. Class “A” (Health care providers & services)		1,185,612		13,024



	Issuer	Shares		Value

	Common Stocks—(continued)

	*Emerging Asia—(continued)*
	China—(continued)
	AK Medical Holdings, Ltd. (Health care equipment & supplies)		750,000	$	1,323
*	Alibaba Group Holding, Ltd. (Internet & direct marketing retail)		1,017,484		28,830
*	Alibaba Health Information Technology, Ltd. (Health care technology)		1,526,000		3,384
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		1,361,600		6,718
	Chacha Food Co., Ltd. Class “A” (Food products)		416,642		2,779
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		807,000		8,720
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		383,165		7,647
	Hangzhou Tigermed Consulting Co., Ltd. Class “A” (Life sciences tools & services)		333,970		9,991
*	JD.com, Inc. Class “A” (Internet & direct marketing retail)		295,700		11,631
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		27,453		8,738
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		1,936,500		23,644
*	Meituan Class “B” (Internet & direct marketing retail)		322,700		13,317
*	NAURA Technology Group Co., Ltd. Class “A” (Semiconductors & semiconductor equipment)		158,913		6,822
	NetEase, Inc. (Entertainment)		661,325		14,982
*	Offcn Education Technology Co., Ltd. Class “A” (Diversified consumer services)		845,721		2,734
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		2,427,000		23,772
	Proya Cosmetics Co., Ltd. Class “A” (Personal products)		157,899		4,807
	Shenzhen Mindray Bio-Medical Electronics Co., Ltd. Class “A” (Health care equipment & supplies)		116,350		8,644
	Silergy Corporation (Semiconductors & semiconductor equipment)		32,000		4,353
*	TAL Education Group—ADR (Diversified consumer services)		170,416		4,300
	Tencent Holdings, Ltd. (Interactive Media & Services)		429,300		32,290
*	Tencent Music Entertainment Group—ADR (Entertainment)		221,496		3,429
*	Topchoice Medical Corporation Class “A” (Health care providers & services)		159,139		10,123
*	Venus MedTech Hangzhou, Inc. Class “H” (Health care equipment & supplies)		393,500		3,282
*	Weimob, Inc. (Software)		1,348,000		2,972
	WuXi AppTec Co., Ltd. Class “A” (Life sciences tools & services)		311,436		7,548
*	Wuxi Biologics Cayman, Inc. (Life sciences tools & services)		1,482,500		27,171
					302,920

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	*Common Stocks—(continued)*

	*Emerging Asia—(continued)*
	India—3.9%
	Crompton Greaves Consumer Electricals, Ltd. (Household durables)		766,384	$	4,472
	Dr. Lal PathLabs, Ltd. (Health care providers & services)		142,034		6,262
	Havells India, Ltd. (Electrical equipment)		293,939		3,875
	HDFC Bank, Ltd. (Banks)		1,136,344		22,886
	Info Edge India, Ltd. (Interactive Media & Services)		63,087		4,184
*	InterGlobe Aviation, Ltd. (Airlines)		281,995		6,532
	Ipca Laboratories, Ltd. (Pharmaceuticals)		106,867		2,916
*	Pidilite Industries, Ltd. (Chemicals)		142,748		4,137
	Reliance Industries, Ltd. (Oil, gas & consumable fuels)		1,194,967		33,579
	Voltas, Ltd. (Construction & engineering)		246,034		3,379
					92,222
	Indonesia—1.0%
	Bank Central Asia Tbk PT (Banks)		11,549,100		23,994
	South Korea—1.3%
	Kakao Corporation (Interactive Media & Services)		123,548		17,882
	Samsung SDI Co., Ltd. (Electronic equipment,instruments & components)		19,596		12,146
					30,028
	Taiwan—3.2%
	Airtac International Group (Machinery)		125,000		4,823
	ASMedia Technology, Inc. (Semiconductors & semiconductor equipment)		59,000		2,848
	Globalwafers Co., Ltd. (Semiconductors & semiconductor equipment)		139,000		4,585
	MediaTek, Inc. (Semiconductors & semiconductor equipment)		737,000		25,446
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors &semiconductor equipment)		310,395		37,297
					74,999
	Thailand—1.0%
	Carabao Group PCL Class “F” (Beverages)		712,500		3,146
*	Sea, Ltd.—ADR (Entertainment)		73,887		20,289
					23,435

	*United Kingdom—11.5%*
	3i Group plc (Capital markets)		476,304		7,729
	Ashtead Group plc (Trading companies & distributors)		561,802		41,686
	Avast plc (Software)		1,188,280		8,051
	AVEVA Group plc (Software)		137,030		7,029
	Big Yellow Group plc (Equity REIT)		255,942		4,627
*	boohoo Group plc (Internet & direct marketing retail)		864,217		3,711
*	Ceres Power Holdings plc (Electrical equipment)		180,907		2,645
*	Compass Group plc (Hotels, restaurants & leisure)		1,209,212		25,458



	Issuer	Shares		Value

	*Common Stocks—(continued)*

	*United Kingdom—(continued)*
	Croda International plc (Chemicals)		179,226	$	18,267
*	CVS Group plc (Health care providers & services)		115,476		3,858
	Diploma plc (Trading companies & distributors)		127,849		5,136
	Experian plc (Professional services)		478,693		18,448
	Halma plc (Electronic equipment, instruments & components)		462,339		17,217
	Intermediate Capital Group plc (Capital markets)		368,581		10,829
	Intertek Group plc (Professional services)		110,867		8,481
	London Stock Exchange Group plc (Capital markets)		197,596		21,785
	Renishaw plc (Electronic equipment, instruments & components)		54,628		3,722
	Rentokil Initial plc (Commercial services & supplies)		1,837,201		12,580
	Rotork plc (Machinery)		1,823,991		8,589
	Segro plc (Equity REIT)		933,118		14,128
	Softcat plc (IT services)		186,480		4,581
	Spirax-Sarco Engineering plc (Machinery)		83,523		15,730
*	Trainline plc (Hotels, restaurants & leisure)		702,877		2,855
*	Trustpilot Group plc (Interactive Media & Services)		775,505		3,662
					270,804

	*Japan—9.2%*
	Asahi Intecc Co., Ltd. (Health care equipment & supplies)		254,500		6,084
*	BASE, Inc. (IT services)		236,800		3,600
	Benefit One, Inc. (Professional services)		172,400		5,424
*	Bengo4.com, Inc. (Interactive Media & Services)		29,900		2,616
	Daikin Industries, Ltd. (Building products)		110,400		20,560
	Disco Corporation (Semiconductors & semiconductor equipment)		10,900		3,331
	Food & Life Cos., Ltd. (Hotels, restaurants & leisure)		131,400		5,671
	GMO Payment Gateway, Inc. (IT services)		44,000		5,731
	Harmonic Drive Systems, Inc. (Machinery)		73,100		4,027
	Hoya Corporation (Health care equipment & supplies)		121,700		16,136
	Keyence Corporation (Electronic equipment, instruments & components)		47,600		24,024
	M3, Inc. (Health care technology)		183,900		13,430
	MISUMI Group, Inc. (Machinery)		187,300		6,339
	MonotaRO Co., Ltd. (Trading companies & distributors)		335,400		7,940
	Nihon M&A Center, Inc. (Professional services)		381,300		9,888

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	*Japan—(continued)*
	Olympus Corporation (Health care equipment & supplies)		848,300	$	16,860
	Omron Corporation (Electronic equipment, instruments & components)		205,500		16,296
	Rakus Co., Ltd. (Software)		195,200		5,333
*	SHIFT, Inc. (IT services)		29,100		4,508
	SMC Corporation (Machinery)		43,400		25,647
	TechnoPro Holdings, Inc. (Professional services)		228,900		5,415
	TIS, Inc. (IT services)		312,600		7,983
					216,843

	*Asia—3.3%*
	Australia—1.5%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		405,474		13,103
*	Atlassian Corporation plc Class “A” (Software)†		57,763		14,837
	Netwealth Group, Ltd. (Capital markets)		297,447		3,826
	Pro Medicus, Ltd. (Health care technology)		98,105		4,320
					36,086
	Hong Kong—1.8%
	AIA Group, Ltd. (Insurance)		3,288,600		40,873

	*Canada—3.0%*
*	Canada Goose Holdings, Inc. (Textiles, apparel & luxury goods)		145,671		6,372
	Canadian National Railway Co. (Road & rail)		327,347		34,538
	Enghouse Systems, Ltd. (Software)		59,565		2,652
*	Kinaxis, Inc. (Software)		30,998		4,078
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		49,944		18,228
*	Nuvei Corporation (IT services)		15,130		1,238
	Toromont Industries, Ltd. (Trading companies & distributors)		45,102		3,930
					71,036

	*Emerging Latin America—2.3%*
	Argentina—0.8%
*	Globant S.A. (IT services)†		27,916		6,118
*	MercadoLibre, Inc. (Internet & direct marketing retail)		8,971		13,975
					20,093
	Brazil—1.2%
	B3 S.A. - Brasil Bolsa Balcao (Capital markets)		2,327,700		7,872
	Locaweb Servicos de Internet S.A. (IT services)		1,489,293		8,103
	Magazine Luiza S.A. (Multiline retail)		1,727,100		7,344
	Notre Dame Intermedica Participacoes S.A. (Health care providers & services)		330,200		5,638
					28,957

	Issuer	Shares or Principal Amount		Value

	Common Stocks—(continued)

	*Emerging Latin America—(continued)*
	Mexico—0.2%
*	Grupo Aeroportuario del Sureste S.A.B. de C.V.—ADR (Transportation infrastructure)		23,134	$	4,277
	Uruguay—0.1%
*	Dlocal, Ltd. (IT services)†		33,408		1,755

	*Emerging Europe—1.0%*
	Poland—0.5%
*	Allegro.eu S.A. (Internet & direct marketing retail)		408,173		7,025
*	InPost S.A. (Air freight & logistics)		247,897		4,975
					12,000
	Russia—0.5%
*	Yandex N.V. Class “A” (Interactive Media & Services)†		164,137		11,612
	Total Common Stocks—99.0% (cost $1,340,147)				2,329,153

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $14,005, collateralized by U.S. Treasury Bond, 1.875%,due 2/15/41, valued at $14,285		$14,005		14,005
	Total Repurchase Agreement—0.6% (cost $14,005)				14,005
	Total Investments—99.6% (cost $1,354,152)				2,343,158
	Cash and other assets, less liabilities—0.4%				9,372
	Net assets—100.0%			$	2,352,530

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

International Growth Fund

Portfolio of Investments, June 30, 2021 (unaudited)

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	26.5	%
Information Technology	20.5	%
Consumer Discretionary	14.6	%
Health Care	13.9	%
Financials	8.6	%
Communication Services	5.0	%
Materials	3.0	%
Energy	2.6	%
Consumer Staples	2.6	%
Real Estate	1.6	%
Utilities	1.1	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	25.7	%
British Pound Sterling	11.6	%
Hong Kong Dollar	10.4	%
Japanese Yen	9.3	%
U.S. Dollar	8.5	%
Swiss Franc	7.0	%
Swedish Krona	6.2	%
Danish Krone	4.1	%
Indian Rupee	4.0	%
Chinese Yuan Renminbi	3.9	%
Canadian Dollar	2.0	%
New Taiwan Dollar	1.8	%
South Korean Won	1.3	%
Brazilian Real	1.2	%
Indonesian Rupiah	1.0	%
All Other Currencies	2.0	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	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 8.49% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. IMI (net) (the “Index”), increased 9.58%. Six-month underperformance versus the Index was primarily driven by negative stock selection across most sectors. Stock selection within the Financials sector was particularly weak, as Ping An Insurance and Bank Central Asia weighed on relative performance in the period. Ping An is the largest insurance company by market cap globally and the leading life insurance in what we expect will be the largest market (by size and growth) for life insurance over the next decade. Although Ping An remains firmly in the expanding growth phase of its corporate lifecycle, its breadth of services propels it into a different category, and closer to becoming a dominant technology-powered retail financial services group. It has developed a broad ecosystem comprising over 6oo million internet users and over 220 million retail customers. Ping An continues to improve its cross-sell of products from other parts of the group, which increases income without incurring the cost of acquiring new clients. While recent results have been below average due to COVID-19, we believe it will revert to its previous growth trajectory as the economy recovers. Partially offsetting these effects was positive stock selection within the Health Care and Communication Services sectors. Within Health Care, Wuxi Biologics and Lonza added to relative returns. Wuxi Biologics is a contract development and manufacturing organization (CDMO) that offers a full range of research and manufacturing services for biologic drugs. The services are designed to help clients improve research and development efficiency, shorten development timelines and lower costs. Importantly, Wuxi is the only company offering comprehensive CDMO services for biologics in China. As a result, Wuxi is the domestic market leader with approximately 50% market share. Supporting Wuxi’s growth profile is strong demand for biologics outsourcing services worldwide. We believe Wuxi’s strong execution and favorable market dynamics will generate strong earnings growth for the foreseeable future. Lonza is a leader in custom manufacturing of biopharmaceuticals and specialty ingredients. Lonza offers highly visible growth and given the strong market demand for outsourced biopharma production and related services, we remain confident it can deliver on growth in the future. Within Communication Services, Kakao boosted relative returns. Kakao is a South Korean online platform. It operates KakaoTalk, the largest mobile messaging app, and Daum, the second largest web portal. Other businesses include ride-hailing, music streaming, and financial services businesses with Kakao Pay and Kakao Bank. We believe Kakao will sustain its position as one of the most dominant tech companies in South Korea, given the strong market position, management execution, business development, and potential to drive synergies and capture sustained value around its various platform, content, and new businesses. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

Semiannual Report

June 30, 2021

Institutional International Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year
Institutional International Growth Fund		8.49	%		42.73	%		16.36	%		15.24	%		9.06	%
MSCI ACW Ex-U.S. IMI (net)		9.58			37.18			9.42			11.20			5.65

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 at www.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.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Institutional International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	Europe, Mid-East—45.3%
	Belgium—0.3%
	Warehouses De Pauw CVA (Equity REIT)		93,950	$	3,587
	Denmark—4.1%
	Chr Hansen Holding A/S (Chemicals)		37,641		3,397
	Coloplast A/S Class “B” (Health care equipment & supplies)		32,790		5,380
	DSV PANALPINA A/S (Air freight & logistics)		100,745		23,495
*	Genmab A/S (Biotechnology)		20,708		8,473
	Netcompany Group A/S (Software)		28,737		3,265
	Orsted A/S (Electric utilities)		47,343		6,643
	Royal Unibrew A/S (Beverages)		21,776		2,774
					53,427
	Finland—0.9%
	Neste Oyj (Oil, gas & consumable fuels)		197,740		12,108
	France—10.4%
*	Airbus SE (Aerospace & defense)		172,817		22,221
	Dassault Systemes SE (Software)		43,297		10,499
	Hermes International (Textiles, apparel & luxury goods)		4,524		6,590
	Kering S.A. (Textiles, apparel & luxury goods)		20,286		17,728
	L’Oreal S.A. (Personal products)		30,286		13,496
	LVMH Moet Hennessy Louis Vuitton SE (Textiles, apparel & luxury goods)		27,872		21,855
	Safran S.A. (Aerospace & defense)		106,101		14,710
	Sartorius Stedim Biotech (Life sciences tools & services)		19,056		9,013
	Teleperformance (Professional services)		40,442		16,415
*	Worldline S.A. (IT services)		55,808		5,224
					137,751
	Germany—5.9%
	Carl Zeiss Meditec AG (Health care equipment & supplies)		31,005		5,991
	CompuGroup Medical SE & Co. KgaA (Health care technology)		32,662		2,558
*	CTS Eventim AG & Co. KGaA (Entertainment)		53,404		3,337
*	HelloFresh SE (Internet & direct marketing retail)		77,872		7,570
*	Hypoport SE (Diversified financial services)		3,624		1,873
	Infineon Technologies AG (Semiconductors & semiconductor equipment)		326,910		13,110
	KION Group AG (Machinery)		47,693		5,083
	MTU Aero Engines AG (Aerospace & defense)		69,438		17,200
	Nemetschek SE (Software)		27,739		2,122
	Puma SE (Textiles, apparel & luxury goods)		83,100		9,908
*	TeamViewer AG (Software)		56,435		2,123
	Vonovia SE (Real estate management & development)		104,344		6,745
					77,620



	Issuer	Shares		Value

	Common Stocks—(continued)

	Europe, Mid-East—(continued)
	Ireland—2.1%
*	ICON plc (Life sciences tools &services)†		44,981	$	9,298
	Kingspan Group plc (Building products)		99,362		9,383
*	Ryanair Holdings plc—ADR (Airlines)		84,288		9,121
					27,802
	Israel—1.0%
*	Inmode, Ltd. (Health care equipment & supplies)†		28,864		2,733
*	Nice, Ltd.—ADR (Software)		11,129		2,754
*	Wix.com, Ltd. (IT services)†		26,314		7,638
					13,125
	Italy—0.7%
	Amplifon SpA (Health care providers & services)		70,532		3,482
*	Brunello Cucinelli SpA (Textiles, apparel & luxury goods)		41,468		2,425
	Moncler SpA (Textiles, apparel & luxury goods)		50,576		3,422
					9,329
	Luxembourg—0.9%
*	Eurofins Scientific SE (Life sciences tools & services)		77,841		8,898
	Tenaris S.A. (Energy equipment & services)		272,119		2,966
					11,864
	Netherlands—3.7%
*	Adyen N.V. (IT services)		5,767		14,090
	ASML Holding N.V. (Semiconductors & semiconductor equipment)		37,646		25,864
	BE Semiconductor Industries N.V. (Semiconductors & semiconductor equipment)		25,251		2,142
	Euronext N.V. (Capital markets)		31,957		3,475
	IMCD N.V. (Trading companies & distributors)		22,082		3,511
					49,082
	Norway—0.7%
*	Pexip Holding ASA (Software)		151,666		1,355
	Scatec ASA (Independent power &renewable electricity producers)		74,415		1,970
	TOMRA Systems ASA (Commercial services & supplies)		99,665		5,498
					8,823
	Spain—1.6%
*	Amadeus IT Group S.A. (IT services)		223,619		15,729
	EDP Renovaveis S.A. (Independent power & renewable electricity producers)		199,760		4,628
*	Solaria Energia y Medio Ambiente S.A. (Independent power & renewable electricity producers)		78,273		1,415
					21,772

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Institutional International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Europe, Mid-East—(continued)
	Sweden—6.1%
	AddTech AB Class “B” (Trading companies & distributors)		124,344	$	2,063
	Atlas Copco AB Class “A” (Machinery)		360,692		22,085
	Beijer Ref AB (Trading companies & distributors)		183,269		3,266
	Evolution Gaming Group AB (Hotels, restaurants & leisure)		68,184		10,775
	Hexagon AB Class “B” (Electronic equipment, instruments &components)		998,618		14,796
	Indutrade AB (Machinery)		198,749		5,086
	Investment AB Latour Class “B” (Industrial conglomerates)		122,022		4,004
	Lifco AB Class “B” (Industrial conglomerates)		155,945		3,644
	Nibe Industrier AB Class “B” (Building products)		492,272		5,178
	Nolato AB Class “B” (Industrial conglomerates)		273,996		2,696
	Sweco AB Class “B” (Construction & engineering)		123,702		2,250
	Thule Group AB (Leisure products)		55,086		2,442
	Vitrolife AB (Biotechnology)		50,783		2,110
					80,395
	Switzerland—6.9%
	Belimo Holding AG (Building products)		5,225		2,389
	Logitech International S.A. (Technology hardware, storage & peripherals)		23,895		2,895
	Lonza Group AG (Life sciences tools & services)		22,877		16,215
	Partners Group Holding AG (Capital markets)		10,325		15,640
	Siegfried Holding AG (Life sciences tools & services)*		3,387		3,176
	SIG Combibloc Group AG (Containers & packaging)*		155,326		4,220
	Sika AG (Chemicals)		59,372		19,411
	Softwareone Holding AG (Electronic equipment, instruments & components)*		76,773		1,813
	Straumann Holding AG (Health care equipment & supplies)		7,114		11,341
	Tecan Group AG (Life sciences tools & services)		7,134		3,534
	Temenos AG (Software)		25,179		4,044
	VAT Group AG (Machinery)		13,148		4,371
*	Zur Rose Group AG (Food & staples retailing)		5,273		2,020
					91,069



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—23.3%
	China—12.9%
	A-Living Smart City Services Co., Ltd. (Commercial services & supplies)		670,250	$	3,336
	Aier Eye Hospital Group Co., Ltd. Class “A” (Health care providers & services)		660,127		7,252
	AK Medical Holdings, Ltd. (Health care equipment & supplies)		422,000		745
*	Alibaba Group Holding, Ltd. (Internet &direct marketing retail)		570,000		16,151
*	Alibaba Health Information Technology, Ltd. (Health care technology)		854,000		1,894
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		762,700		3,763
	Chacha Food Co., Ltd. Class “A” (Food products)		233,400		1,557
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		452,000		4,884
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		214,612		4,283
	Hangzhou Tigermed Consulting Co., Ltd. Class “A” (Life sciences tools & services)		187,100		5,597
*	JD.com, Inc. Class “A” (Internet & direct marketing retail)		165,650		6,516
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		15,317		4,875
	Li Ning Co., Ltd. (Textiles, apparel &luxury goods)		1,084,500		13,241
*	Meituan Class “B” (Internet & direct marketing retail)		180,700		7,457
	NAURA Technology Group Co., Ltd. Class “A” (Semiconductors & semiconductor equipment)*		89,000		3,821
	NetEase, Inc. (Entertainment)		370,400		8,391
	Offcn Education Technology Co., Ltd. Class “A” (Diversified consumer services)		473,700		1,532
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		1,359,500		13,316
	Proya Cosmetics Co., Ltd. Class “A” (Personal products)		88,500		2,694
	Shenzhen Mindray Bio-Medical Electronics Co., Ltd. Class “A” (Health care equipment & supplies)		65,200		4,844
	Silergy Corporation (Semiconductors & semiconductor equipment)		18,000		2,448
*	TAL Education Group—ADR (Diversified consumer services)		95,456		2,408
	Tencent Holdings, Ltd. (Interactive Media & Services)		240,500		18,089
*	Tencent Music Entertainment Group—ADR (Entertainment)		124,068		1,921
*	Topchoice Medical Corporation Class “A” (Health care providers & services)		89,200		5,674

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Institutional International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	China—(continued)
*	Venus MedTech Hangzhou, Inc. Class “H” (Health care equipment & supplies)		220,500	$	1,839
*	Weimob, Inc. (Software)		755,000		1,665
	WuXi AppTec Co., Ltd. Class “A” (Life sciences tools & services)		174,456		4,228
*	Wuxi Biologics Cayman, Inc. (Life sciences tools & services)		830,500		15,221
					169,642
	India—3.9%
	Crompton Greaves Consumer Electricals, Ltd. (Household durables)		429,278		2,505
	Dr. Lal PathLabs, Ltd. (Health care providers & services)		79,558		3,507
	Havells India, Ltd. (Electrical equipment)		164,645		2,171
	HDFC Bank, Ltd. (Banks)		636,506		12,819
	Info Edge India, Ltd. (Interactive Media & Services)		35,337		2,344
*	InterGlobe Aviation, Ltd. (Airlines)		157,955		3,659
	Ipca Laboratories, Ltd. (Pharmaceuticals)		59,860		1,633
*	Pidilite Industries, Ltd. (Chemicals)		79,958		2,318
	Reliance Industries, Ltd. (Oil, gas &consumable fuels)		669,208		18,806
	Voltas, Ltd. (Construction & engineering)		138,355		1,900
					51,662
	Indonesia—1.0%
	Bank Central Asia Tbk PT (Banks)		6,469,106		13,440
	South Korea—1.3%
	Kakao Corporation (Interactive Media & Services)		69,204		10,017
	Samsung SDI Co., Ltd. (Electronic equipment, instruments & components)		10,976		6,803
					16,820
	Taiwan—3.2%
	Airtac International Group (Machinery)		70,000		2,701
	ASMedia Technology, Inc. (Semiconductors & semiconductor equipment)		33,000		1,593
	Globalwafers Co., Ltd. (Semiconductors & semiconductor equipment)		78,000		2,573
	MediaTek, Inc. (Semiconductors & semiconductor equipment)		413,000		14,259
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		173,863		20,891
					42,017
	Thailand—1.0%
	Carabao Group PCL Class “F” (Beverages)		399,100		1,762
*	Sea, Ltd.—ADR (Entertainment)		41,387		11,365
					13,127



	Issuer	Shares		Value

	Common Stocks—(continued)

	United Kingdom—11.5%
	3i Group plc (Capital markets)		266,795	$	4,329
	Ashtead Group plc (Trading companies & distributors)		314,685		23,350
	Avast plc (Software)		665,597		4,510
	AVEVA Group plc (Software)		76,755		3,937
	Big Yellow Group plc (Equity REIT)		143,362		2,592
*	boohoo Group plc (Internet & direct marketing retail)		484,078		2,079
*	Ceres Power Holdings plc (Electrical equipment)		101,332		1,482
*	Compass Group plc (Hotels, restaurants & leisure)		677,322		14,260
	Croda International plc (Chemicals)		100,391		10,232
*	CVS Group plc (Health care providers & services)		64,610		2,158
	Diploma plc (Trading companies & distributors)		71,613		2,877
	Experian plc (Professional services)		268,132		10,333
	Halma plc (Electronic equipment, instruments & components)		258,972		9,644
	Intermediate Capital Group plc (Capital markets)		206,455		6,066
	Intertek Group plc (Professional services)		62,101		4,751
	London Stock Exchange Group plc (Capital markets)		110,680		12,202
	Renishaw plc (Electronic equipment, instruments & components)		30,599		2,085
	Rentokil Initial plc (Commercial services & supplies)		1,029,080		7,046
	Rotork plc (Machinery)		1,021,681		4,811
	Segro plc (Equity REIT)		522,672		7,913
	Softcat plc (IT services)		104,454		2,566
	Spirax-Sarco Engineering plc (Machinery)		46,784		8,811
*	Trainline plc (Hotels, restaurants & leisure)		393,706		1,599
*	Trustpilot Group plc (Interactive Media & Services)		434,387		2,051
					151,684

	Japan—9.2%
	Asahi Intecc Co., Ltd. (Health care equipment & supplies)		142,500		3,407
*	BASE, Inc. (IT services)		132,700		2,017
	Benefit One, Inc. (Professional services)		96,600		3,039
*	Bengo4.com, Inc. (Interactive Media & Services)		16,900		1,479
	Daikin Industries, Ltd. (Building products)		61,800		11,509
	Disco Corporation (Semiconductors & semiconductor equipment)		6,100		1,864
	Food & Life Cos., Ltd. (Hotels, restaurants & leisure)		73,600		3,177
	GMO Payment Gateway, Inc. (IT services)		24,600		3,204

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Institutional International Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Japan—(continued)
	Harmonic Drive Systems, Inc. (Machinery)		41,000	$	2,259
	Hoya Corporation (Health care equipment & supplies)		68,200		9,043
	Keyence Corporation (Electronic equipment, instruments & components)		26,600		13,425
	M3, Inc. (Health care technology)		103,000		7,522
	MISUMI Group, Inc. (Machinery)		104,900		3,550
	MonotaRO Co., Ltd. (Trading companies & distributors)		187,800		4,446
	Nihon M&A Center, Inc. (Professional services)		213,600		5,539
	Olympus Corporation (Health care equipment & supplies)		475,200		9,444
	Omron Corporation (Electronic equipment, instruments & components)		115,100		9,128
	Rakus Co., Ltd. (Software)		109,400		2,989
*	SHIFT, Inc. (IT services)		16,300		2,525
	SMC Corporation (Machinery)		24,300		14,360
	TechnoPro Holdings, Inc. (Professional services)		128,100		3,030
	TIS, Inc. (IT services)		175,100		4,471
					121,427
	Asia—3.3%
	Australia—1.5%
	Aristocrat Leisure, Ltd. (Hotels, restaurants & leisure)		227,120		7,339
*	Atlassian Corporation plc Class “A” (Software)†		32,355		8,311
	Netwealth Group, Ltd. (Capital markets)		166,610		2,143
	Pro Medicus, Ltd. (Health care technology)		54,952		2,420
					20,213
	Hong Kong—1.8%
	AIA Group, Ltd. (Insurance)		1,842,063		22,895

	Canada—3.0%
*	Canada Goose Holdings, Inc. (Textiles, apparel & luxury goods)†		81,595		3,569
	Canadian National Railway Co. (Road & rail)		183,359		19,346
	Enghouse Systems, Ltd. (Software)		33,590		1,496
*	Kinaxis, Inc. (Software)		17,363		2,284
*	Lululemon Athletica, Inc. (Textiles, apparel & luxury goods)		27,976		10,210
*	Nuvei Corporation (IT services)		8,467		693
	Toromont Industries, Ltd. (Trading companies & distributors)		25,263		2,201
					39,799

	Issuer	Share or Principal Amount		Value

	Common Stocks—(continued)

	Emerging Latin America—2.3%
	Argentina—0.8%
*	Globant S.A. (IT services)†		15,637	$	3,427
*	MercadoLibre, Inc. (Internet & direct marketing retail)		5,025		7,828
					11,255
	Brazil—1.2%
	B3 S.A. - Brasil Bolsa Balcao (Capital markets)		1,303,800		4,409
	Locaweb Servicos de Internet S.A. (IT services)		834,186		4,538
	Magazine Luiza S.A. (Multiline retail)		967,400		4,114
	Notre Dame Intermedica Participacoes S.A. (Health care providers & services)		185,000		3,159
					16,220
	Mexico—0.2%
*	Grupo Aeroportuario del Sureste S.A.B. de C.V.—ADR (Transportation infrastructure)		12,958		2,396
	Uruguay—0.1%
	*Dlocal, Ltd. (IT services)†		18,633		979

	Emerging Europe—1.0%
	Poland—0.5%
*	Allegro.eu S.A. (Internet & direct marketing retail)		228,632		3,934
*	InPost S.A. (Air freight & logistics)		138,856		2,787
					6,721
	Russia—0.5%
*	Yandex N.V. Class “A” (Interactive Media & Services)†		91,939		6,505
	Total Common Stocks—98.9% (cost $746,376)				1,304,556

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $7,763, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $7,918		$7,763		7,763
	Total Repurchase Agreement—0.6% (cost $7,763)				7,763
	Total Investments—99.5% (cost $754,139)				1,312,319
	Cash and other assets, less liabilities—0.5%				6,488
	Net assets—100.0%			$	1,318,807

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Institutional International Growth Fund

Portfolio of Investments, June 30, 2021 (unaudited)

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	26.5	%
Information Technology	20.5	%
Consumer Discretionary	14.6	%
Health Care	13.9	%
Financials	8.6	%
Communication Services	5.0	%
Materials	3.0	%
Energy	2.6	%
Consumer Staples	2.6	%
Real Estate	1.6	%
Utilities	1.1	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Euro	25.7	%
British Pound Sterling	11.6	%
Hong Kong Dollar	10.4	%
Japanese Yen	9.3	%
U.S. Dollar	8.5	%
Swiss Franc	7.0	%
Swedish Krona	6.2	%
Danish Krone	4.1	%
Indian Rupee	4.0	%
Chinese Yuan Renminbi	3.8	%
Canadian Dollar	2.0	%
New Taiwan Dollar	1.8	%
South Korean Won	1.3	%
Brazilian Real	1.3	%
Indonesian Rupiah	1.0	%
All Other Currencies	2.0	%
Total	100.0	%

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	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, CFA D.J. Neiman, CFA	The William Blair International Small Cap Growth Fund (Class N shares) posted a 7.28% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI All Country World ex-U.S. Small Cap Index (net) (the “Index”), increased 12.24%. Underperformance for the six-month period was driven primarily by stock selection within the Industrials and Information Technology sectors, which had been the strongest contributors in 2020. Within Industrials, Japanese automation company Harmonic Drive Systems was the largest detractor. Harmonic Drive dominates its niche in small speed reducers (80% market share), resulting in consistently high profitability and returns. Long running relationships with robot original equipment manufacturers, technical advantages for a high cost of failure product, and scale are competitive advantages. The share price weakened during the period despite a strong recovery in orders (+63% year over year for the company’s fiscal fourth quarter), and management’s increased operating income guidance for the 2022 fiscal year which exceeded consensus estimates. Within the Information Technology sector, Japanese holdings Nihon Unisys and Hennge KK were the largest detractors. Nihon Unisys is a traditional IT services vendor based in Japan. The company still has a large part of its business in traditional IT services, but it has focused more on building standardized products that it can deliver to multiple clients, improving operating margins and creating more stable revenues. Negative revenue growth during the fourth quarter was driven by system services declining due to low demand for legacy system development projects. Smaller projects continued to be pushed-out by customers due to the COVID-19 pandemic, while operating expenses related to order activities stayed high, driving a decline in earnings before interest and taxes. These negative effects were partially mitigated by positive stock selection within the Health Care and Real Estate sectors. Within Health Care, Australia-based Pro Medicus was the top contributor during the period. We believe that the company has developed a best-of-breed software solution for medical imaging. Through its proprietary streaming architecture, its platform has evolved to become the market leader in viewer speed, implementation speed, clinical efficiency, and cost benefits. Real Estate sector performance was bolstered by real estate investment trust holding Safestore, one of the leading self-storage companies in the UK, with operations in both the UK and Paris. Within Real Estate, the self-storage category has been resilient amid the COVID-19 pandemic, and Safestore’s share price was supported by a strong second quarter trading update amid robust occupancy levels and an increase in the development pipeline. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

June 30, 2021

William Blair Funds

International Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		7.28	%		42.47	%		13.37	%		12.93	%		8.38	%
Class I		7.42			42.79			13.66			13.25			8.69
Class R6		7.49			42.98			13.79			13.37			8.85
MSCI ACW Ex-U.S. Small Cap Index (net)		12.24			47.04			9.78			11.97			7.02

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	Europe, Mid-East—38.5%
	Belgium—1.9%
	Melexis N.V. (Semiconductors & semiconductor equipment)		39,897	$	4,142
	Warehouses De Pauw CVA (Equity REIT)		77,877		2,974
					7,116
	Denmark—0.7%
	Netcompany Group A/S (Software)		22,112		2,512
	Finland—0.8%
*	Musti Group Oyj (Specialty retail)		81,284		3,009
	Germany—4.2%
	Carl Zeiss Meditec AG (Health care equipment & supplies)		16,984		3,282
	CompuGroup Medical SE & Co. KgaA (Health care technology)		34,729		2,720
*	CTS Eventim AG & Co. KGaA (Entertainment)		36,420		2,276
*	Hypoport SE (Diversified financial services)		7,211		3,728
*	Westwing Group AG (Internet & direct marketing retail)		60,085		3,287
					15,293
	Israel—1.8%
*	Inmode, Ltd. (Health care equipment & supplies)†		56,007		5,303
*	NEOGAMES S.A. (Hotels, restaurants & leisure)†		20,863		1,282
					6,585
	Italy—2.8%
	Amplifon SpA (Health care providers & services)		125,374		6,190
*	Brunello Cucinelli SpA (Textiles, apparel & luxury goods)		37,631		2,201
	Carel Industries SpA (Electronic equipment, instruments & components)		83,043		1,994
					10,385
	Netherlands—0.5%
	BE Semiconductor Industries N.V. (Semiconductors & semiconductor equipment)		22,400		1,900
	Norway—1.5%
*	Pexip Holding ASA (Software)		203,240		1,815
	TOMRA Systems ASA (Commercial services & supplies)		70,326		3,880
					5,695
	Spain—2.1%
	EDP Renovaveis S.A. (Independent power & renewable electricity producers)		214,671		4,974
*	Solaria Energia y Medio Ambiente S.A. (Independent power & renewable electricity producers)		144,613		2,613
					7,587



	Issuer	Shares		Value

	Common Stocks—(continued)

	Europe, Mid-East—(continued)
	Sweden—16.7%
	AddTech AB Class “B” (Trading companies & distributors)		318,627	$	5,287
	Arjo AB Class “B” (Health care equipment & supplies)		516,904		5,327
	Beijer Ref AB (Trading companies & distributors)		402,735		7,177
	Biotage AB (Life sciences tools & services)		113,910		2,697
*	Hemnet Group AB (Interactive Media & Services)		54,858		1,234
	Indutrade AB (Machinery)		97,042		2,483
	Investment AB Latour Class “B” (Industrial conglomerates)		199,103		6,533
	Lagercrantz Group AB (Electronic equipment, instruments & components)		86,095		937
	Lifco AB Class “B” (Industrial conglomerates)		245,505		5,737
	MIPS AB (Leisure products)		81,444		7,004
	Nolato AB Class “B” (Industrial conglomerates)		430,560		4,236
	Paradox Interactive AB (Entertainment)		60,432		1,271
*	Sdiptech AB (Commercial services & supplies)		53,161		2,711
	Sweco AB Class “B” (Construction & engineering)		188,210		3,424
	Vitrolife AB (Biotechnology)		129,358		5,375
					61,433
	Switzerland—5.5%
	Belimo Holding AG (Building products)		7,060		3,228
	Kardex Holding AG (Machinery)		15,183		3,512
*	Siegfried Holding AG (Life sciences tools & services)		4,440		4,163
*	Softwareone Holding AG (Electronic equipment, instruments & components)		144,672		3,416
	Tecan Group AG (Life sciences tools & services)		4,205		2,083
*	Zur Rose Group AG (Food & staples retailing)		9,668		3,704
					20,106

	*Emerging Asia—18.0%*
	Cambodia—0.9%
	NagaCorp, Ltd. (Hotels, restaurants & leisure)		3,290,000		3,174
	China—5.9%
	A-Living Smart City Services Co., Ltd. (Commercial services & supplies)		675,750		3,364
	AK Medical Holdings, Ltd. (Health care equipment & supplies)		1,552,000		2,738
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		1,026,890		5,067
	Chacha Food Co., Ltd. Class “A” (Food products)		346,400		2,311

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	China—(continued)
	Changzhou Xingyu Automotive Lighting Systems Co., Ltd. Class “A” (Auto components)		51,962	$	1,815
*	iClick Interactive Asia Group, Ltd.—ADR (Media)		63,987		706
	Proya Cosmetics Co., Ltd. Class “A” (Personal products)		88,744		2,702
*	Venus MedTech Hangzhou, Inc. Class “H” (Health care equipment & supplies)		359,500		2,998
					21,701
	India—6.4%
*	Aavas Financiers, Ltd. (Thrifts & mortgage finance)		53,092		1,906
*	Affle India, Ltd. (Media)		18,917		1,095
*	AU Small Finance Bank, Ltd. (Banks)		361,548		5,056
*	IndiaMart InterMesh, Ltd. (Trading companies & distributors)		17,990		1,694
	Info Edge India, Ltd. (Interactive Media & Services)		42,809		2,839
	Ipca Laboratories, Ltd. (Pharmaceuticals)		140,634		3,837
*	Motherson Sumi Systems, Ltd. (Auto components)		2,167,643		7,071
					23,498
	Indonesia—0.3%
	Ace Hardware Indonesia Tbk PT (Specialty retail)		14,560,400		1,255
	Malaysia—0.2%
	MR DIY Group M Bhd (Specialty retail)		829,400		717
	South Korea—0.9%
	Koh Young Technology, Inc. (Semiconductors & semiconductor equipment)		155,575		3,288
	Taiwan—3.4%
	ASPEED Technology, Inc. (Semiconductors & semiconductor equipment)		35,000		2,525
	Globalwafers Co., Ltd. (Semiconductors & semiconductor equipment)		84,000		2,771
	momo.com, Inc. (Internet & direct marketing retail)		45,000		3,044
	Voltronic Power Technology Corporation (Electrical equipment)		85,451		4,125
					12,465

	Japan—15.3%
*	BASE, Inc. (IT services)		222,000		3,375
	BayCurrent Consulting, Inc. (Professional services)		19,900		7,147
	Benefit One, Inc. (Professional services)		177,600		5,587
*	Bengo4.com, Inc. (Interactive Media & Services)		35,000		3,062
	Food & Life Cos., Ltd. (Hotels, restaurants & leisure)		129,400		5,585
	GMO Payment Gateway, Inc. (IT services)		17,400		2,266
	Harmonic Drive Systems, Inc. (Machinery)		56,800		3,129



	Issuer	Shares		Value

	Common Stocks—(continued)

	Japan—(continued)
*	Hennge KK (IT services)		33,200	$	1,137
	Japan Elevator Service Holdings Co., Ltd. (Commercial services & supplies)		140,700		3,270
	JINS Holdings, Inc. (Specialty retail)		65,900		5,048
	Rakus Co., Ltd. (Software)		196,100		5,357
*	SHIFT, Inc. (IT services)		19,000		2,944
	SMS Co., Ltd. (Professional services)		136,500		4,086
	TechnoPro Holdings, Inc. (Professional services)		187,500		4,436
					56,429

	United Kingdom—11.6%
	AVEVA Group plc (Software)		34,987		1,795
*	Beazley plc (Insurance)		525,433		2,416
*	boohoo Group plc (Internet & direct marketing retail)		852,300		3,660
	Burford Capital, Ltd. (Diversified financial services)		189,113		1,946
*	Ceres Power Holdings plc (Electrical equipment)		36,688		537
*	CVS Group plc (Health care providers & services)		49,337		1,648
	Diploma plc (Trading companies & distributors)		85,899		3,451
	dotdigital group plc (Software)		554,606		1,772
	IntegraFin Holdings plc (Capital markets)		476,338		3,393
*	Moonpig Group plc (Internet & direct marketing retail)		134,701		799
	Renishaw plc (Electronic equipment, instruments & components)		37,466		2,553
	Rotork plc (Machinery)		764,677		3,601
	Safestore Holdings plc (Equity REIT)		474,956		6,222
	Softcat plc (IT services)		203,902		5,009
*	Trainline plc (Hotels, restaurants & leisure)		531,151		2,157
*	Trustpilot Group plc (Interactive Media & Services)		406,859		1,921
					42,880

	Emerging Latin America—3.9%
	Brazil—2.3%
	Arezzo Industria e Comercio S.A. (Textiles, apparel & luxury goods)		201,900		3,836
	Locaweb Servicos de Internet S.A. (IT services)		312,700		1,701
	Pet Center Comercio e Participacoes S.A. (Specialty retail)		557,800		2,889
					8,426
	Mexico—1.6%
*	Grupo Aeroportuario del Centro Norte S.A.B. de C.V. (Transportation infrastructure)		893,400		5,852

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

International Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

	Issuer	Share or Principal Amount		Value

	Common Stocks—(continued)

	Canada—3.2%
*	Canada Goose Holdings, Inc. (Textiles, apparel & luxury goods)†		47,620	$	2,083
	Enghouse Systems, Ltd. (Software)		67,474		3,004
*	Kinaxis, Inc. (Software)		29,380		3,865
	Toromont Industries, Ltd. (Trading companies & distributors)		32,515		2,833
					11,785

	Asia—2.8%
	Australia—2.2%
*	Nanosonics, Ltd. (Health care equipment & supplies)		397,052		1,748
	Netwealth Group, Ltd. (Capital markets)		150,464		1,935
	Pro Medicus, Ltd. (Health care technology)		96,971		4,271
					7,954
	New Zealand—0.6%
	Ryman Healthcare, Ltd. (Health care providers & services)		258,029		2,368

	Mid-East, Africa—1.8%
	South Africa—0.9%
	Clicks Group, Ltd. (Food & staples retailing)		197,447		3,397
	United Arab Emirates—0.9%
*	Network International Holdings plc (IT services)		650,987		3,292
	Total Common Stocks—95.1% (cost $267,772)				350,102

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $7,595, collateralized by U.S. Treasury Bond, 1.875% due 2/15/41, valued at $7,746		$7,595		7,595
	Total Repurchase Agreement—2.1% (cost $7,595)				7,595
	Total Investments—97.2% (cost $275,367)				357,697
	Cash and other assets, less liabilities—2.8%				10,243
	Net assets—100.0%			$	367,940

ADR = American Depository Receipt

REIT = Real Estate Investment Trust

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Industrials	31.0	%
Information Technology	17.5	%
Consumer Discretionary	17.1	%
Health Care	16.2	%
Financials	5.8	%
Communication Services	4.1	%
Consumer Staples	3.5	%
Real Estate	2.6	%
Utilities	2.2	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Swedish Krona	17.5	%
Japanese Yen	16.1	%
British Pound Sterling	13.2	%
Euro	12.9	%
Indian Rupee	6.7	%
Swiss Franc	5.7	%
New Taiwan Dollar	3.6	%
Hong Kong Dollar	3.5	%
Chinese Yuan Renminbi	3.4	%
Canadian Dollar	2.8	%
U.S. Dollar	2.7	%
Brazilian Real	2.4	%
Australian Dollar	2.3	%
Mexican Peso	1.7	%
Norwegian Krone	1.6	%
All Other Currencies	3.9	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Emerging Markets Leaders Fund

	The Emerging Markets Leaders Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Todd M. McClone, CFA John C. Murphy, CFA	The William Blair Emerging Markets Leaders Fund (Class N shares) posted a 3.70% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets Index (net) (the “Index”) increased 7.45%. Six-month underperformance versus the Index was driven by a combination of allocation and stock selection effects. An underweight allocation to Materials, coupled with weak stock selection within the Financials and Consumer Discretionary sectors weighed on relative returns. Within the Financials sector, Ping An Insurance Group detracted from relative results. The stock declined on continued weakness in their value of new business (VNB), compounded by ongoing restructuring of their Life business. This was further impacted by credit losses because of the default of China Fortune Land Development. Credicorp of Peru also weighed on relative results amid uncertainty regarding Presidential elections in Peru. Midea Group hurt relative performance in the Consumer Discretionary sector. The stock price declined due to increased profit margin pressure on the back of soaring raw material prices and the slow uptick in demand amid relatively cool summer weather. Partially offsetting these effects was positive stock selection within the Communication Services and Materials sectors. Within Communication Services, Kakao Corp. and Sea Ltd. bolstered relative results amid continued strong business trends. UPL Ltd., the Indian agrochemical company, outperformed within the Materials sector amid robust volume growth, favorable agriculture commodity prices and an encouraging growth outlook. We believe that the company continues to gain market share amid increased product innovation and strong execution. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

Semiannual Report

June 30, 2021

Emerging Markets Leaders Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		3.70	%		38.11	%		14.30	%		13.84	%		5.55	%
Class I		3.84			38.33			14.59			14.14			5.85
Class R6		3.92			38.42			14.64			14.19			5.93
MSCI Emerging Markets Index (net)		7.45			40.90			11.27			13.03			4.28

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 at www.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.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Emerging Markets Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	Emerging Asia—76.3%
	China—34.6%
	Aier Eye Hospital Group Co., Ltd. Class “A” (Health care providers & services)		314,686	$	3,457
*	Alibaba Group Holding, Ltd. (Internet & direct marketing retail)		808,628		22,912
	China Tourism Group Duty Free Corporation, Ltd. Class “A” (Specialty retail)		116,856		5,427
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		144,500		2,884
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		14,659		4,666
	Midea Group Co., Ltd. Class “A” (Household durables)		505,100		5,579
	NetEase, Inc. (Entertainment)		504,350		11,426
	Ping An Insurance Group Co. of China, Ltd. Class “H” (Insurance)		956,000		9,364
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		117,200		2,960
*	TAL Education Group—ADR (Diversified consumer services)		53,687		1,355
	Tencent Holdings, Ltd. (Interactive Media & Services)		317,100		23,851
*	Tencent Music Entertainment Group—ADR (Entertainment)		369,682		5,723
	TravelSky Technology, Ltd. Class “H” (IT services)		1,664,000		3,592
	Zhangzhou Pientzehuang Pharmaceutical Co., Ltd. Class “A” (Pharmaceuticals)		90,400		6,272
					109,468
	India—18.1%
	Asian Paints, Ltd. (Chemicals)		85,508		3,453
*	Bajaj Finance, Ltd. (Consumer finance)		39,309		3,178
	Britannia Industries, Ltd. (Food products)		54,972		2,702
	HDFC Bank, Ltd. (Banks)		370,619		7,464
	Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		129,568		4,319
	Infosys, Ltd. (IT services)		384,374		8,171
*	InterGlobe Aviation, Ltd. (Airlines)		140,970		3,265
*	Motherson Sumi Systems, Ltd. (Auto components)		1,938,870		6,324
	Reliance Industries, Ltd. (Oil, gas & consumable fuels)		418,568		11,710
	UPL, Ltd. (Chemicals)		636,325		6,797
					57,383
	Indonesia—1.5%
	Bank Central Asia Tbk PT (Banks)		2,206,500		4,584
	South Korea—8.4%
*	Coupang, Inc. (Internet & direct marketing retail)		86,565		3,620
	Douzone Bizon Co., Ltd. (Software)		36,636		2,700
	Kakao Corporation (Interactive Media & Services)		41,992		6,078
	LG Household & Health Care, Ltd. (Personal products)		4,632		7,247
	NAVER Corporation (Interactive Media & Services)		18,945		7,024
					26,669



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	Taiwan—11.7%
	E.Sun Financial Holding Co., Ltd. (Banks)		3,091,301	$	2,918
*	eMemory Technology, Inc. (Semiconductors & semiconductor equipment)		39,000		1,869
	MediaTek, Inc. (Semiconductors & semiconductor equipment)		213,000		7,354
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		207,150		24,891
					37,032
	Thailand—2.0%
*	Sea, Ltd.—ADR (Entertainment)		23,292		6,396

	Emerging Latin America—14.6%
	Argentina—3.9%
*	Globant S.A. (IT services)†		23,488		5,148
*	MercadoLibre, Inc. (Internet & direct marketing retail)		4,658		7,256
					12,404
	Brazil—6.0%
	B3 S.A. - Brasil Bolsa Balcao (Capital markets)		1,822,300		6,162
	Raia Drogasil S.A. (Food & staples retailing)		435,500		2,164
*	Rumo S.A. (Road & rail)		1,586,800		6,109
	TOTVS S.A. (Software)		610,800		4,624
					19,059
	Mexico—3.3%
*	Grupo Aeroportuario del Pacifico S.A.B. de C.V. Class “B” (Transportation infrastructure)		560,500		6,001
	Wal-Mart de Mexico S.A.B. de C.V. (Food & staples retailing)		1,326,800		4,334
					10,335
	Peru—1.4%
*	Credicorp, Ltd. (Banks)†		35,226		4,266

	Emerging Europe, Mid-East, Africa—8.5%
	Poland—0.9%
*	Allegro.eu S.A. (Internet & direct marketing retail)		161,372		2,777
	Russia—3.6%
	HeadHunter Group plc—ADR (Professional services)		110,658		4,689
*	Yandex N.V. Class “A” (Interactive Media & Services)†		97,321		6,885
					11,574
	South Africa—3.1%
	Capitec Bank Holdings, Ltd. (Banks)		53,400		6,307
	Clicks Group, Ltd. (Food & staples retailing)		202,099		3,477
					9,784

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Leaders Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

	Issuer	Shares or Principal Amount		Value

	Common Stocks—(continued)

	Emerging Europe, Mid-East, Africa—(continued)
	United Arab Emirates—0.9%
*	Network International Holdings plc (IT services)		546,240	$	2,763
	Total Common Stocks—99.4% (cost $233,492)				314,494

	Corporate Obligation

	Emerging Asia—0.0%
	India—0.0%
*	Britannia Industries, Ltd. (Food products)	$	1,388,984		19
	Total Corporate Obligations—(0.0)% (cost $19)				19

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $29,547, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $30,138	$	29,547		29,547
	Total Repurchase Agreement—9.3% (cost $29,547)				29,547
	Total Investments—108.7% (cost $263,058)				344,060
	Liabilities, plus cash and other assets—(8.7)%				(27,525	)
	Net assets—100.0%			$	316,535

ADR = American Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Communication Services	21.5	%
Information Technology	19.4	%
Consumer Discretionary	18.5	%
Financials	15.4	%
Consumer Staples	8.7	%
Industrials	6.4	%
Energy	3.7	%
Materials	3.3	%
Health Care	3.1	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Hong Kong Dollar	23.6	%
U.S. Dollar	22.3	%
Indian Rupee	18.1	%
Chinese Yuan Renminbi	9.0	%
South Korean Won	7.3	%
Brazilian Real	6.0	%
New Taiwan Dollar	3.9	%
Mexican Peso	3.3	%
South African Rand	3.1	%
Indonesian Rupiah	1.5	%
All Other Currencies	1.9	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Emerging Markets Growth Fund

	The Emerging Markets Growth Fund seeks long-term capital appreciation.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Todd M. McClone, CFA Casey K. Preyss, CFA Vivian Lin Thurston, CFA	The William Blair Emerging Markets Growth Fund (Class N shares) posted a 10.37% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets IMI (net) (the “Index”), increased 8.75%. Six-month outperformance versus the Index was primarily driven by positive stock selection across most sectors. Stock selection within the Communication Services sector was particularly strong, propelled by Kakao Corp. and Sea Ltd. We believe that Kakao’s strong operating momentum across all divisions and the upcoming initial public offering of its fintech businesses lifted the share price. Sea Ltd. continued to outperform on the back of strong momentum in its gaming business with Free Fire leading in Latin America, Southeast Asia and India, and accelerating growth in its ecommerce business amid increasing penetration and market share gains. Partially offsetting these effects was the underweight allocation to the Materials sector, coupled with below average stock selection within the Industrials and Consumer Staples sectors. Within Industrials, the lack of the exposure to Taiwanese shipping companies which rallied in the second quarter hurt relative performance. Jiangsu Hengli Hydraulic Co., the Chinese machinery company specializing in the manufacturing of hydraulic cylinders, hindered relative results in the first quarter of 2021 as the stock weakened amid the decelerating machinery cycle in China. Within the Consumer Staples sector, Foshan Haitian Flavouring & Food, the largest condiments producer in China, also hindered relative results. The stock underperformance was due to increased raw materials prices and broad market rotation in the first quarter. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

Semiannual Report

June 30, 2021

Emerging Markets Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		10.37	%		50.16	%		18.81	%		17.39	%		7.65	%
Class I		10.50			50.49			19.13			17.69			7.94
Class R6		10.56			50.70			19.22			17.79			8.07
MSCI Emerging Markets IMI (net)		8.75			43.21			11.38			12.86			4.31

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 at www.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.

Sector Diversification (Unaudited)

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

June 30, 2021

William Blair Funds

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	Emerging Asia—86.1%
	China—29.6%
	Aier Eye Hospital Group Co., Ltd. Class “A” (Health care providers & services)		490,377	$	5,387
*	Alibaba Group Holding, Ltd. (Internet & direct marketing retail)		945,832		26,800
	ANTA Sports Products, Ltd. (Textiles, apparel & luxury goods)		437,000		10,289
*	BeiGene, Ltd. (Biotechnology)		117,900		3,207
	Beijing Oriental Yuhong Waterproof Technology Co., Ltd. Class “A” (Construction materials)		523,230		4,480
	By-health Co., Ltd. Class “A” (Personal products)		598,700		3,048
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		1,190,800		5,875
	China Education Group Holdings, Ltd. (Diversified consumer services)		1,555,000		3,469
	China Meidong Auto Holdings, Ltd. (Specialty retail)		1,096,000		5,978
	China Merchants Bank Co., Ltd. Class “H” (Banks)		2,159,000		18,422
	China Tourism Group Duty Free Corporation, Ltd. Class “A” (Specialty retail)		174,258		8,093
	Chongqing Zhifei Biological Products Co., Ltd. Class “A” (Biotechnology)		138,000		3,988
*	Contemporary Amperex Technology Co., Ltd. Class “A” (Electrical equipment)		131,100		10,851
	Country Garden Services Holdings Co., Ltd. (Commercial services & supplies)		1,148,000		12,405
	Foshan Haitian Flavouring & Food Co., Ltd. Class “A” (Food products)		231,765		4,625
	Hangzhou Tigermed Consulting Co., Ltd. Class “A” (Life sciences tools & services)		223,566		6,688
*	JD.com, Inc. Class “A” (Internet & direct marketing retail)		262,450		10,323
	Jiumaojiu International Holdings, Ltd. (Hotels, restaurants & leisure)		1,329,000		5,435
*	Kingdee International Software Group Co., Ltd. (Software)		722,000		2,450
	Kweichow Moutai Co., Ltd. Class “A” (Beverages)		28,642		9,117
	Li Ning Co., Ltd. (Textiles, apparel & luxury goods)		1,330,000		16,239
*	Meituan Class “B” (Internet & direct marketing retail)		265,500		10,956
	NetEase, Inc. (Entertainment)		762,500		17,274
	Shenzhen Inovance Technology Co., Ltd. Class “A” (Machinery)		662,864		7,618
	Shenzhen Mindray Bio-Medical Electronics Co., Ltd. Class “A” (Health care equipment & supplies)		109,168		8,111
	Shenzhou International Group Holdings, Ltd. (Textiles, apparel & luxury goods)		361,000		9,118
	Silergy Corporation (Semiconductors & semiconductor equipment)		157,000		21,356



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	China—(continued)
	Tencent Holdings, Ltd. (Interactive Media & Services)		764,360	$	57,492
*	Topchoice Medical Corporation Class “A” (Health care providers & services)		69,100		4,395
*	Wuliangye Yibin Co., Ltd. Class “A” (Beverages)		208,894		9,631
	WuXi AppTec Co., Ltd. Class “H” (Life sciences tools & services)		473,460		11,056
*	Wuxi Biologics Cayman, Inc. (Life sciences tools & services)		1,110,000		20,344
	Zhangzhou Pientzehuang Pharmaceutical Co., Ltd. Class “A” (Pharmaceuticals)		140,329		9,736
	Zhongsheng Group Holdings, Ltd. (Specialty retail)		1,003,500		8,349
					372,605
	India—18.2%
	Aarti Industries, Ltd. (Chemicals)		248,062		2,913
*	Affle India, Ltd. (Media)		40,294		2,333
*	Amber Enterprises India, Ltd. (Household durables)		72,372		2,844
*	APL Apollo Tubes, Ltd. (Metals & mining)		179,840		3,944
	Apollo Hospitals Enterprise, Ltd. (Health care providers & services)		109,155		5,313
	Asian Paints, Ltd. (Chemicals) Astral Poly Technik, Ltd.		198,321		8,010
	(Building products)		146,761		3,929
*	Atul, Ltd. (Chemicals)		24,978		2,994
*	Bajaj Finance, Ltd. (Consumer finance)		74,788		6,046
	Balkrishna Industries, Ltd. (Auto components)		140,707		4,255
	Coforge, Ltd. (IT services)		73,977		4,141
	Crompton Greaves Consumer Electricals, Ltd. (Household durables)		790,913		4,615
	Dabur India, Ltd. (Personal products)		557,895		4,264
*	Divi’s Laboratories, Ltd. (Life sciences tools & services)		97,639		5,786
*	Dixon Technologies India, Ltd. (Household durables)		89,331		5,302
	Dr. Lal PathLabs, Ltd. (Health care providers & services)		90,379		3,984
	Escorts, Ltd. (Machinery)		152,102		2,503
	Havells India, Ltd. (Electrical equipment)		367,880		4,850
	HDFC Bank, Ltd. (Banks)		917,898		18,486
	HDFC Life Insurance Co., Ltd. (Insurance)		272,068		2,518
	Hindustan Unilever, Ltd. (Household products)		129,997		4,329
	Housing Development Finance Corporation, Ltd. (Thrifts & mortgage finance)		430,060		14,336
*	IndiaMart InterMesh, Ltd. (Trading companies & distributors)		28,562		2,689
	Indraprastha Gas, Ltd. (Gas utilities)		409,610		3,069
	Info Edge India, Ltd. (Interactive Media & Services)		84,534		5,607
*	JK Cement, Ltd. (Construction materials)		71,541		2,744

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	India—(continued)
	Kajaria Ceramics, Ltd. (Building products)		230,553	$	3,030
	Larsen & Toubro Infotech, Ltd. (IT services)		52,699		2,886
	Laurus Labs Ltd. (Pharmaceuticals)		508,338		4,729
*	MakeMyTrip, Ltd. (Hotels, restaurants & leisure)†		79,438		2,387
	Metropolis Healthcare, Ltd. (Health care providers & services)		80,017		3,030
	Navin Fluorine International, Ltd. (Chemicals)		66,394		3,354
	Nestle India, Ltd. (Food products)		14,139		3,370
	PI Industries, Ltd. (Chemicals)		135,084		5,309
*	Pidilite Industries, Ltd. (Chemicals)		219,877		6,373
	Reliance Industries, Ltd. (Oil, gas & consumable fuels)		765,204		21,196
	SRF, Ltd. (Chemicals)		68,084		6,668
	Tata Consultancy Services, Ltd. (IT services)		279,286		12,591
	Tata Consumer Products, Ltd. (Food products)		461,410		4,694
	Tata Elxsi, Ltd. (Software)		89,012		5,209
	UPL, Ltd. (Chemicals)		545,582		5,828
	Varun Beverages, Ltd. (Beverages)		327,666		3,216
	Voltas, Ltd. (Construction & engineering)		220,997		3,036
					228,710
	Indonesia—1.1%
	Bank Central Asia Tbk PT (Banks)		4,254,999		8,840
	Bank Rakyat Indonesia Persero Tbk PT (Banks)		17,791,100		4,834
					13,674
	South Korea—14.6%
	Hansol Chemical Co., Ltd. (Chemicals)		23,864		5,202
	JYP Entertainment Corporation (Entertainment)		64,224		2,310
	Kakao Corporation (Interactive Media & Services)		275,221		39,836
	Koh Young Technology, Inc. (Semiconductors & semiconductor equipment)		125,151		2,645
	LEENO Industrial, Inc. (Semiconductors & semiconductor equipment)		32,125		5,007
	LG Household & Health Care, Ltd. (Personal products)		6,155		9,630
	NAVER Corporation (Interactive Media & Services)		57,658		21,376
	NCSoft Corporation (Entertainment)		7,258		5,285
	NICE Information Service Co., Ltd. (Professional services)		135,551		3,021
	PI Advanced Materials Co., Ltd. (Chemicals)		75,308		3,678
	Samsung Electronics Co., Ltd. (Technology hardware, storage & peripherals)		861,021		61,701
	Samsung SDI Co., Ltd. (Electronic equipment, instruments & components)		13,345		8,271



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	South Korea—(continued)
	SK Hynix, Inc. (Semiconductors & semiconductor equipment)		109,747	$	12,425
	WONIK IPS Co., Ltd. (Semiconductors & semiconductor equipment)		83,051		3,658
					184,045
	Taiwan—20.3%
	Accton Technology Corporation (Communications equipment)		369,000		4,377
	Advantech Co., Ltd. (Technology hardware, storage & peripherals)		339,766		4,207
	Airtac International Group (Machinery)		358,000		13,812
	ASMedia Technology, Inc. (Semiconductors & semiconductor equipment)		61,000		2,945
	ASPEED Technology, Inc. (Semiconductors & semiconductor equipment)		122,000		8,801
*	Chailease Holding Co., Ltd. (Diversified financial services)		1,269,000		9,223
	Chroma ATE, Inc. (Electronic equipment, instruments & components)		524,000		3,601
	E.Sun Financial Holding Co., Ltd. (Banks)		4,324,313		4,082
	Elite Material Co., Ltd. (Electronic equipment, instruments & components)		498,000		3,896
*	eMemory Technology, Inc. (Semiconductors & semiconductor equipment)		115,000		5,510
	Globalwafers Co., Ltd. (Semiconductors & semiconductor equipment)		138,000		4,552
	Hiwin Technologies Corporation (Machinery)		224,000		3,176
	Lotes Co., Ltd. (Electronic equipment, instruments & components)		214,000		4,485
	MediaTek, Inc. (Semiconductors & semiconductor equipment)		1,204,000		41,570
*	momo.com, Inc. (Internet & direct marketing retail)		113,000		7,645
	Parade Technologies, Ltd. (Semiconductors & semiconductor equipment)		151,000		7,506
*	Poya International Co., Ltd. (Multiline retail)		100,000		1,949
	Realtek Semiconductor Corporation (Semiconductors & semiconductor equipment)		489,000		8,863
	Sinbon Electronics Co., Ltd. (Electronic equipment, instruments & components)		555,000		5,458
	Taiwan Semiconductor Manufacturing Co., Ltd.—ADR (Semiconductors & semiconductor equipment)		635,033		76,306
	Taiwan Semiconductor Manufacturing Co., Ltd. (Semiconductors & semiconductor equipment)		1,073,000		22,914
	Voltronic Power Technology Corporation (Electrical equipment)		120,586		5,821
	Wiwynn Corporation (Technology hardware, storage & peripherals)		131,000		4,687
					255,386

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Emerging Markets Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	Thailand—1.4%
	Com7 PCL Class “F” (Specialty retail)		1,590,600	$	3,462
*	Sea, Ltd.—ADR (Entertainment)		54,856		15,063
					18,525
	Vietnam—0.9%
	Hoa Phat Group JSC (Metals & mining)		4,940,001		11,054

	Emerging Europe, Africa—7.1%
	Kenya—0.3%
	Safaricom plc (Wireless telecommunication services)		9,013,654		3,508
	Poland—1.3%
*	Allegro.eu S.A. (Internet & direct marketing retail)		352,581		6,068
*	Dino Polska S.A. (Food & staples retailing)		94,603		6,944
*	InPost S.A. (Air freight & logistics)		196,668		3,947
					16,959
	Russia—3.2%
*	Ozon Holdings plc—ADR (Internet & direct marketing retail)		72,421		4,245
	TCS Group Holding plc—GDR (Banks)		202,406		17,711
*	Yandex N.V. Class “A” (Interactive Media & Services)†		257,862		18,244
					40,200
	South Africa—2.3%
	Capitec Bank Holdings, Ltd. (Banks)		100,167		11,830
	Clicks Group, Ltd. (Food & staples retailing)		233,027		4,009
	Naspers, Ltd. Class “N” (Internet & direct marketing retail)		60,163		12,632
					28,471

	Emerging Latin America—7.0%
	Argentina—1.6%
*	Globant S.A. (IT services)†		29,388		6,441
*	MercadoLibre, Inc. (Internet & direct marketing retail)		8,879		13,832
					20,273
	Brazil—4.5%
	B3 S.A. - Brasil Bolsa Balcao (Capital markets)		1,842,200		6,230
	Localiza Rent a Car S.A. (Road & rail)		438,300		5,640
	Locaweb Servicos de Internet S.A. (IT services)		862,900		4,695
	Magazine Luiza S.A. (Multiline retail)		1,624,900		6,909
	Patria Investments, Ltd. Class “A” (Capital markets)†		206,741		3,643
	Raia Drogasil S.A. (Food & staples retailing)		1,145,600		5,691
*	StoneCo, Ltd. Class “A” (IT services)†		95,928		6,433
	TOTVS S.A. (Software)		924,500		6,998



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Latin America—(continued)
	Brazil—(continued)
*	Vinci Partners Investments, Ltd. Class “A” (Capital markets)†		233,097	$	3,380
	WEG S.A. (Electrical equipment)		1,012,640		6,859
					56,478
	Mexico—0.5%
	Wal-Mart de Mexico S.A.B. de C.V. (Food & staples retailing)		1,840,800		6,012
	Uruguay—0.4%
*	Dlocal, Ltd. (IT services)†		88,615		4,655
	Total Common Stocks—100.2% (cost $826,669)				1,260,555
	Total Investments—100.2% (cost $826,669)				1,260,555
	Liabilities, plus cash and other assets—(0.2)%				(2,045	)
	Net assets—100.0%			$	1,258,510

ADR = American Depository Receipt

GDR = Global Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Information Technology	30.2	%
Consumer Discretionary	15.2	%
Communication Services	14.9	%
Financials	10.3	%
Industrials	7.9	%
Health Care	7.6	%
Consumer Staples	6.2	%
Materials	5.8	%
Energy	1.7	%
Utilities	0.2	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Hong Kong Dollar	19.8	%
Indian Rupee	17.9	%
New Taiwan Dollar	15.9	%
South Korean Won	14.6	%
U.S. Dollar	13.7	%
Chinese Yuan Renminbi	8.1	%
Brazilian Real	3.4	%
South African Rand	2.3	%
Indonesian Rupiah	1.1	%
Polish Zloty	1.0	%
All Other Currencies	2.2	%
Total	100.0	%

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	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, CFA Casey K. Preyss, CFA D.J. Neiman, CFA	The William Blair Emerging Markets Small Cap Growth Fund (Class N shares) (the “Fund”) posted a 13.55% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the MSCI Emerging Markets Small Cap Index (net) (the “Index”), increased 19.78%. Six-month underperformance versus the Index was primarily driven by negative stock selection across most sectors amid the broad style headwind. Stock selection within the Industrials sector was particularly weak, hurt by lack of exposure to Marine Transportation and Machinery names. Zhejiang Dingli Machinery, the largest supplier of aerial working platforms in China, and Randon Implementos, the Brazilian truck and automotive equipment manufacturer, dragged down results within the Machinery industry. Escorts, the Indian tractor manufacturer, also detracted to relative performance as COVID-19 concerns led to downward revisions to earnings estimates. Partially offsetting these effects was positive stock selection within the Consumer Discretionary and Health Care sectors. Within Consumer Discretionary, Momo.com and F&F Holdings were notable contributors on the back of strong performance in the second quarter. Ovctek China Inc and Laurus Labs Ltd enhanced relative returns within the Health Care sector. Ovctek is the domestic leader and a pioneer of OrthoK lenses in China. The company continued to deliver strong fundamental performance amid robust demand, and margin improvement from a favorable product mix and the company’s transition to a direct sales model. Please refer to the Global Markets Review and Outlook relating to the Fund beginning on page 29.

June 30, 2021

William Blair Funds

Emerging Markets Small Cap Growth Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021

	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		13.55	%		48.67	%		15.13	%		12.67	%		11.94	%
Class I(a)		13.71			49.10			15.43			13.00			12.25
MSCI Emerging Markets Small Cap Index (net)(a)		19.78			63.75			12.31			11.86			7.04
Class R6(b)		13.73			49.20			15.49			13.06			10.77
MSCI Emerging Markets Small Cap Index (net)(b)		19.78			63.75			12.31			11.86			6.53

(a)	Since inception is for the period from October 24, 2011 (Commencement of Operations) to June 30, 2021.
(b)	Since inception is for the period from December 20, 2012 (Commencement of Operations) to June 30, 2021.

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 at www.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.

Sector Diversification (Unaudited)

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

Semiannual Report

June 30, 2021

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks

	Emerging Asia—80.2%
	Cambodia—0.2%
	NagaCorp, Ltd. (Hotels, restaurants & leisure)		856,000	$	826
	China—14.1%
	A-Living Smart City Services Co., Ltd. (Commercial services & supplies)		740,500		3,686
	By-health Co., Ltd. Class “A” (Personal products)		1,032,500		5,257
	Centre Testing International Group Co., Ltd. Class “A” (Professional services)		2,531,705		12,491
	Chacha Food Co., Ltd. Class “A” (Food products)		156,173		1,042
	Changzhou Xingyu Automotive Lighting Systems Co., Ltd. Class “A” (Auto components)		121,735		4,253
	China Lesso Group Holdings, Ltd. (Building products)		1,686,000		4,161
	China Meidong Auto Holdings, Ltd. (Specialty retail)		670,000		3,654
*	Estun Automation Co., Ltd. Class “A” (Machinery)		459,000		2,774
	Ever Sunshine Lifestyle Services Group, Ltd. (Commercial services & supplies)		1,662,000		4,127
*	iClick Interactive Asia Group, Ltd.—ADR (Media)		175,660		1,939
	Jiumaojiu International Holdings, Ltd. (Hotels, restaurants & leisure)		2,047,000		8,371
	JNBY Design, Ltd. (Textiles, apparel & luxury goods)		712,000		1,265
*	Kingsoft Cloud Holdings, Ltd.—ADR (IT services)		21,413		726
	Ovctek China, Inc. Class “A” (Health care equipment & supplies)		120,006		1,923
	Proya Cosmetics Co., Ltd. Class “A” (Personal products)		173,824		5,292
	Shanghai M&G Stationery, Inc. Class “A” (Commercial services & supplies)		138,319		1,810
	Skshu Paint Co., Ltd. Class “A” (Chemicals)		116,363		3,170
*	Weimob, Inc. (Software)		1,535,000		3,385
					69,326
	India—35.3%
	Aarti Industries, Ltd. (Chemicals)		582,732		6,844
*	Aavas Financiers, Ltd. (Thrifts & mortgage finance)		71,661		2,573
*	Affle India, Ltd. (Media)		50,739		2,938
*	Amber Enterprises India, Ltd. (Household durables)		56,959		2,238
	Apollo Hospitals Enterprise, Ltd. (Health care providers & services)		55,654		2,709
	Astral Poly Technik, Ltd. (Building products)		318,088		8,516
*	Atul, Ltd. (Chemicals)		67,431		8,083
*	AU Small Finance Bank Ltd. (Banks)		632,417		8,844
	Balkrishna Industries, Ltd. (Auto components)		267,928		8,103



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	India—(continued)
	Berger Paints India, Ltd. (Chemicals)		117,586	$	1,275
	Cholamandalam Investment and Finance Co., Ltd. (Consumer finance)		691,128		4,769
	City Union Bank, Ltd. (Banks)		732,830		1,642
	Coforge, Ltd. (IT services)		103,695		5,804
	Computer Age Management Services, Ltd. (IT services)		93,286		3,508
	Crompton Greaves Consumer Electricals, Ltd. (Household durables)		463,942		2,707
*	Dixon Technologies India, Ltd. (Household durables)		89,971		5,340
	Dr. Lal PathLabs, Ltd. (Health care providers & services)		93,030		4,101
*	Endurance Technologies, Ltd. (Auto components)		59,371		1,294
*	Godrej Properties, Ltd. (Real estate management & development)		193,880		3,638
	Havells India, Ltd. (Electrical equipment)		75,382		994
	HDFC Asset Management Co., Ltd. (Capital markets)		18,627		731
*	IndiaMart InterMesh Ltd. (Trading companies & distributors)		25,641		2,414
	Indraprastha Gas, Ltd. (Gas utilities)		200,319		1,501
*	JK Cement, Ltd. (Construction materials)		94,659		3,631
	Kajaria Ceramics, Ltd. (Building products)		90,303		1,187
	Kansai Nerolac Paints, Ltd. (Chemicals)		307,741		2,310
*	KEC International, Ltd. (Construction & engineering)		126,246		774
	Larsen & Toubro Infotech Ltd. (IT services)		99,520		5,451
	Laurus Labs Ltd. (Pharmaceuticals)		541,230		5,035
*	MakeMyTrip, Ltd. (Hotels, restaurants & leisure)†		58,439		1,756
	Metropolis Healthcare, Ltd. (Health care providers & services)		95,347		3,610
*	Motherson Sumi Systems, Ltd. (Auto components)		1,230,554		4,014
	Navin Fluorine International, Ltd. (Chemicals)		113,957		5,757
*	Oberoi Realty, Ltd. (Real estate management & development)		363,119		3,070
	PI Industries, Ltd. (Chemicals)		165,023		6,486
*	Pidilite Industries, Ltd. (Chemicals)		26,073		756
	Radico Khaitan, Ltd. (Beverages)		328,814		3,347
*	RBL Bank, Ltd. (Banks)		348,999		988
*	Relaxo Footwears, Ltd. (Textiles, apparel & luxury goods)		320,210		4,963
	SRF, Ltd. (Chemicals)		84,322		8,259
	Sundram Fasteners, Ltd. (Auto components)		164,973		1,799
	Tata Elxsi, Ltd. (Software)		113,242		6,627
	Trent, Ltd. (Multiline retail)		343,958		3,931
*	V-Mart Retail, Ltd. (Multiline retail)		29,504		1,119
	Varun Beverages, Ltd. (Beverages)		611,448		6,002
	Vinati Organics, Ltd. (Chemicals)		71,863		1,771
					173,209

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	Indonesia—0.4%
	PT Bank Tabungan Pensiunan Nasional Syariah Tbk (Banks)		9,273,700	$	1,842
	Malaysia—1.3%
	Inari Amertron Bhd (Electronic equipment, instruments & components)		5,925,000		4,524
	MR DIY Group M Bhd (Specialty retail)		2,238,800		1,936
					6,460
	Philippines—1.1%
	International Container Terminal Services, Inc. (Transportation infrastructure)		630,560		2,115
	Wilcon Depot, Inc. (Specialty retail)		7,721,600		3,187
					5,302
	South Korea—9.4%
*	Doosan Fuel Cell Co., Ltd. (Electrical equipment)		19,309		857
	Douzone Bizon Co., Ltd. (Software)		14,768		1,089
*	F&F Co., Ltd. (Textiles, apparel & luxury goods)		19,881		9,886
	Hansol Chemical Co., Ltd. (Chemicals)		33,293		7,258
	LEENO Industrial, Inc. (Semiconductors & semiconductor equipment)		50,471		7,865
*	NHN KCP Corporation (IT services)		51,323		2,648
	NICE Information Service Co., Ltd. (Professional services)		267,310		5,958
	PI Advanced Materials Co., Ltd. (Chemicals)		100,351		4,901
	RFHIC Corporation (Semiconductors & semiconductor equipment)		7,960		281
	WONIK IPS Co., Ltd. (Semiconductors & semiconductor equipment)		116,704		5,140
					45,883
	Taiwan—15.6%
	Airtac International Group (Machinery)		211,000		8,141
	Alchip Technologies, Ltd. (Semiconductors & semiconductor equipment)		57,000		1,250
	ASMedia Technology, Inc. (Semiconductors & semiconductor equipment)		26,000		1,255
	ASPEED Technology, Inc. (Semiconductors & semiconductor equipment)		133,000		9,595
	Elite Material Co., Ltd. (Electronic equipment, instruments & components)		533,000		4,170
*	eMemory Technology, Inc. (Semiconductors & semiconductor equipment)		155,000		7,427
	Hiwin Technologies Corporation (Machinery)		160,106		2,270
	Lotes Co., Ltd. (Electronic equipment, instruments & components)		240,000		5,030
	Makalot Industrial Co., Ltd. (Textiles, apparel & luxury goods)		361,000		3,550
*	momo.com, Inc. (Internet & direct marketing retail)		123,000		8,321
	Parade Technologies, Ltd. (Semiconductors & semiconductor equipment)		134,000		6,661



	Issuer	Shares		Value

	Common Stocks—(continued)

	Emerging Asia—(continued)
	Taiwan—(continued)
*	Poya International Co., Ltd. (Multiline retail)		111,000	$	2,163
	RichWave Technology Corporation (Semiconductors & semiconductor equipment)		105,000		1,826
	Sinbon Electronics Co., Ltd. (Electronic equipment, instruments & components)		799,000		7,857
	Sporton International, Inc. (Professional services)		261,000		2,248
	Voltronic Power Technology Corporation (Electrical equipment)		103,507		4,997
					76,761
	Thailand—2.1%
	Carabao Group PCL Class “F” (Beverages)		124,000		547
	Com7 PCL Class “F” (Specialty retail)		2,935,800		6,389
	Muangthai Capital PCL (Consumer finance)		1,945,200		3,490
					10,426
	Vietnam—0.7%
	Hoa Phat Group JSC (Metals & mining)		1,516,220		3,393

	Emerging Latin America—12.0%
	Brazil—9.3%
*	Aeris Industria E Comercio De Equipamentos Para Geracao De Energia S.A. (Electrical equipment)		648,500		1,293
	Arezzo Industria e Comercio S.A. (Textiles, apparel & luxury goods)		167,600		3,184
*	Azul S.A.—ADR (Airlines)		136,068		3,592
	Cyrela Brazil Realty S.A. Empreendimentos e Participacoes (Household durables)		158,300		743
*	Grupo SBF S.A. (Specialty retail)		267,100		2,055
*	Infracommerce CXAAS S.A. (Interactive Media & Services)		671,000		3,208
	Locaweb Servicos de Internet S.A. (IT services)		1,690,578		9,198
	Pet Center Comercio e Participacoes S.A. (Specialty retail)		1,215,600		6,296
*	Sequoia Logistica e Transportes S.A. (Air freight & logistics)		661,500		3,743
	TOTVS S.A. (Software)		1,625,600		12,305
					45,617
	Mexico—2.0%
*	Grupo Aeroportuario del Centro Norte S.A.B. de C.V. (Transportation infrastructure)		689,799		4,519
*	Grupo Aeroportuario del Sureste S.A.B. de C.V. Class “B” (Transportation infrastructure)		297,510		5,477
					9,996
	Uruguay—0.7%
*	Dlocal, Ltd. (IT services)†		64,324		3,379

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Small Cap Growth Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

	Issuer	Shares or Principal Amount		Value

	Common Stocks—(continued)

	Emerging Europe, Mid-East, Africa—8.5%
	Greece—0.7%
	Terna Energy S.A. (Independent power & renewable electricity producers)		233,614	$	3,296
	Kenya—0.8%
	Safaricom plc (Wireless telecommunication services)		10,331,200		4,022
	Poland—1.4%
*	Dino Polska S.A. (Food & staples retailing)		92,425		6,785
	Russia—3.7%
	HeadHunter Group plc—ADR (Professional services)		152,513		6,462
*	Ozon Holdings plc—ADR (Internet & direct marketing retail)		58,407		3,424
	TCS Group Holding plc—GDR (Banks)		96,302		8,426
					18,312
	South Africa—1.4%
	Clicks Group, Ltd. (Food & staples retailing)		70,316		1,210
	Transaction Capital, Ltd. (Consumer finance)		2,115,179		5,602
					6,812
	United Arab Emirates—0.5%
	Abu Dhabi National Oil Co. for Distribution PJSC (Specialty retail)		2,307,721		2,720
	Total Common Stocks—100.7% (cost $385,723)				494,367

	Repurchase Agreement
	Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $2,969, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $3,029		$2,969		2,969
	Total Repurchase Agreement—0.6% (cost $2,969)				2,969
	Total Investments—101.3% (cost $388,692)				497,336
	Liabilities, plus cash and other assets—(1.3)%				(6,482	)
	Net assets—100.0%			$	490,854

ADR = American Depository Receipt

GDR = Global Depository Receipt

* = Non-income producing security

† = U.S. listed foreign security

At June 30, 2021, the Fund’s Portfolio of Investments includes the following industry categories (as a percentage of long-term investments):

Information Technology	23.7	%
Consumer Discretionary	22.1	%
Industrials	19.1	%
Materials	12.9	%
Financials	7.9	%
Consumer Staples	6.0	%
Health Care	3.5	%
Communication Services	2.4	%
Real Estate	1.4	%
Utilities	1.0	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes the following currency categories (as a percentage of long-term investments):

Indian Rupee	34.7	%
New Taiwan Dollar	15.5	%
South Korean Won	9.3	%
Brazilian Real	8.5	%
Chinese Yuan Renminbi	7.7	%
U.S. Dollar	6.0	%
Hong Kong Dollar	5.9	%
Thai Baht	2.1	%
Mexican Peso	2.0	%
South African Rand	1.4	%
Polish Zloty	1.4	%
Malaysian Ringgit	1.3	%
Philippine Peso	1.1	%
All Other Currencies	3.1	%
Total	100.0	%

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Fixed Income Market Review and Outlook

The Bloomberg Barclays U.S. Aggregate Index decreased 1.60% in the first half of 2021. Treasury yields peaked at 1.74% for the 10-year in March, driven by an improving economic outlook as the COVID-19 vaccine continued to roll out, fiscal stimulus, record amounts of Treasury issuance, and rising inflation expectations. In the second quarter intermediate and long-end Treasury yields fell as optimism was tempered by weaker-than-expected data, which reinforced the Federal Reserve’s (Fed) accommodative posture and “transitory” inflation narrative. With rising yields as a headwind to start the year, longer-dated assets such as U.S. Treasuries, Investment Grade Corporates, Agencies, Emerging Market Debt and Mortgage-Backed Securities sectors posted negative returns. On the positive side, improving economic conditions and falling default expectations aided the outperformance of high yield corporate debt, while increasing inflation expectations supported the performance of U.S. Treasury Inflation-Protected Securities (TIPS).

Markit Purchasing Managers Index (PMI) readings improved in the first half of the year, topping out in May as Services touched 70.4, and Manufacturing hit 62.1, where measurements of 50+ are considered expansionary. The pace of COVID-19-driven relocation home purchases slowed, down to 5.8 million after hitting a high of 6.7 million in October 2020. In a sign of strength for the consumer, credit card delinquencies continued to fall, hitting lows in May. New vehicle purchases hit a high in April but reverted to the lower end of the 15-16 million unit range at the end of June, and the value of used cars hit their high point in May before slowing in June.

The Fed’s Federal Open Market Committee (FOMC) held rates steady in the period and reiterated their commitment to maintaining an accommodative stance to generate moderately higher inflation and reduce the jobless rate. The Fed did adjust the floor for overnight rates (“IOER,” Interest on Excess Reserves, and “RRP,” Reverse Repo Program) by +5 basis points to address collateral needs in that segment of the market. The Fed has communicated that they will not hike Federal Funds rates in 2021, and the markets are pricing in 1-2 hikes starting in 2022. The Fed’s balance sheet pushed north of $8 trillion as it continued open market purchases, also known as quantitative easing, to enable looser monetary conditions.

Our base case is that the FOMC will not hike rates in 2021, which will hold short-end rates to the zero lower-bound, despite recent adjustments to the floor. Further, we believe that the FOMC will be very patient in reducing or removing stimulus and tightening monetary conditions. In this environment we continue to find that TIPS are an attractive alternative to fixed-rate Treasuries to mitigate the effects of rising rates driven by accelerating inflationary pressures.

In our opinion spread sectors remain relatively attractive to Treasuries over the intermediate-to-long term as Treasury supply has been increasing at record levels. However, in the shorter-term, if economic data disappoints to the downside, Treasuries could outperform. Within corporate bonds, it appears that security selection will continue to be critical going forward as certain industries and business models are more adapted to successfully navigating the post-COVID-19 pandemic environment than others. Nominal yields are near all-time lows but we believe tight spreads and valuations are supported by strong fundamentals. Default projections have improved, and companies continued to be opportunistic in issuance, extending maturities, and managing their debt profile.

We continue to look for opportunities in the mortgage sector given the potential for attractive spreads, income generation, and duration profile. The sector also benefits from the fundamental tailwind provided by the undersupply of housing. We are also focused on pre-payment speeds given greater refinancing activity driven by factors such as higher home prices, lower interest rates, and new technology.

In asset-backed securities, we are looking for opportunities within autos and credit cards as the consumer is recovering after entering the COVID-19 pandemic in a relatively stronger position compared to previous periods. Our focus has been on prime borrowers, who have continued to do well.

Semiannual Report

June 30, 2021

	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

Ruta Ziverte Vesta Marks, CFA, CAIA	The William Blair Bond Fund (Class N shares) returned a 1.23% decrease, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark, the Bloomberg Barclays U.S. Aggregate Index (the “Index”), decreased 1.60%. The Fund outperformed the Index in the first half of the year as security selection and sector allocation drove excess returns, which offset the negative performance impact of rising yields in the first quarter. The yield curve steepened in the first half of the year as longer-term yields rose while front-end (under two years maturity) yields declined modestly. Our underweight to U.S. Treasuries, driven by valuations, was the largest contributor to relative performance. Within the Treasury sector we opted to use a portion of our allocation to invest in inflation-linked U.S. Treasury Inflation-Protected Securities as they looked attractive versus nominal Treasuries as inflation expectations rose in the period. We held an overweight position in agency mortgage-backed securities (“MBS”) in the period and security selection within the sector drove relative performance as coupon income outweighed the negative performance impact of rising rates. The Federal Reserve has been actively purchasing lower-coupon agency MBS to support the housing market. We have held an underweight in this portion of the market given poor valuations, low income, and longer duration profile, which has benefitted relative performance as this segment underperformed the rest of the sector. The asset allocation decision to invest in high yield corporate debt benefitted performance as this was the best performing sector of the market given falling default expectations. Security selection in emerging markets debt was also beneficial for performance as Fund holdings outperformed the emerging markets debt portion of the Index. Conversely, the Fund’s emphasis of non-cyclical and long-maturity high grade bonds detracted from performance as the yield curve steepened and corporate performance favored cyclical names. Overall, interest rate positioning was a relative detractor from an attribution perspective, driven primarily by the Fund’s positioning in agency MBS and investment grade corporate debt. The use of credit default swap index hedging, used to reduce credit exposure at the margin, detracted from performance as credit spreads tightened in the period. Please refer to the Fixed Income Market Review and Outlook relating to the Fund on page 72.

June 30, 2021

William Blair Funds

Bond Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		(1.23	)%		1.93	%		5.65	%		3.46	%		3.86	%
Class I		(1.09	)		2.16			5.79			3.64			4.04
Class R6		(1.16	)		2.12			5.85			3.70			4.13
Bloomberg Barclays U.S. Aggregate Index		(1.60	)		(0.33	)		5.34			3.03			3.39

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, 2021. 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.

Semiannual Report

June 30, 2021

Bond Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount			Value

U.S. Government and U.S. Government Agency—51.9%
U.S. Treasury Inflation Indexed Notes/Bonds—7.0%
U.S. Treasury Inflation Indexed Bond, 3.875%, due 4/15/29	$	11,937		$	16,804
U.S. Treasury Inflation Indexed Bond, 3.375%, due 4/15/32		541			800
U.S. Treasury Inflation Indexed Bond, 1.375%, due 2/15/44		4,176			5,781
Total U.S. Treasury Inflation Indexed Notes/Bonds					23,385
U.S. Treasury—7.8%
U.S. Treasury Bill, 0.101%, due 7/15/21		1,000			1,000
U.S. Treasury Bill, 0.123%, due 10/7/21(a)		2,000			1,999
U.S. Treasury Bond, 1.125%, due 5/15/40		2,000			1,729
U.S. Treasury Bond, 2.375%, due 11/15/49		2,267			2,416
U.S. Treasury Bond, 1.250%, due 5/15/50		1,500			1,226
U.S. Treasury Note, 0.350%, due 10/31/21		5,000			5,005
U.S. Treasury Note, 1.125%, due 2/28/27		2,250			2,268
U.S. Treasury Note, 0.625%, due 5/15/30		2,100			1,965
U.S. Treasury Note, 0.625%, due 8/15/30		4,300			4,010
U.S. Treasury Strip Principal, 0.000%, due 8/15/27		4,750			4,451
Total U.S. Treasury					26,069
Federal Home Loan Mortgage Corp. (FHLMC)—9.1%
#G30255, 7.000%, due 7/1/21		—			—	^(b)
#J02986, 6.500%, due 7/1/21		—			—	^(b)
#G02210, 7.000%, due 12/1/28		23			26
#G02183, 6.500%, due 3/1/30		3			3
#G01400, 7.000%, due 4/1/32		293			346
#G01728, 7.500%, due 7/1/32		48	��		57
#C01385, 6.500%, due 8/1/32		37			43
#ZT1221, 5.500%, due 1/1/33		420			485
#C01623, 5.500%, due 9/1/33		42			49
#A15039, 5.500%, due 10/1/33		2			2
#A17603, 5.500%, due 1/1/34		1,104			1,287
#G01843, 6.000%, due 6/1/35		8			10
#A62858, 6.500%, due 7/1/37		54			62
#G03170, 6.500%, due 8/1/37		95			113
#A78138, 5.500%, due 6/1/38		106			121
#G04466, 5.500%, due 7/1/38		7,876			9,282
#G60366, 6.000%, due 10/1/39		7,528			9,004
#G61450, 6.000%, due 4/1/40		7,943			9,511
#C03665, 9.000%, due 4/1/41		165			200
Total FHLMC Mortgage Obligations					30,601
Federal National Mortgage Association (FNMA)—28.0%
#900725, 6.000%, due 8/1/21		—			—	^(b)
#893325, 7.000%, due 9/1/21		—			—	^(b)
#735104, 7.000%, due 5/1/22		—			—	^(b)


Issuer	Principal Amount		Value

U.S. Government and U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#255956, 5.500%, due 10/1/25	$	4	$	5
#252925, 7.500%, due 12/1/29		—		1
#AD0729, 7.500%, due 12/1/30		2,023		2,353
#535977, 6.500%, due 4/1/31		3		4
#253907, 7.000%, due 7/1/31		1		1
#587849, 6.500%, due 11/1/31		4		4
#545437, 7.000%, due 2/1/32		23		26
#545759, 6.500%, due 7/1/32		191		226
#545869, 6.500%, due 7/1/32		658		775
#670385, 6.500%, due 9/1/32		283		334
#254548, 5.500%, due 12/1/32		17		20
#AD0725, 7.000%, due 12/1/32		946		1,130
#555340, 5.500%, due 4/1/33		144		168
#741850, 5.500%, due 9/1/33		228		263
#555800, 5.500%, due 10/1/33		20		23
#756153, 5.500%, due 11/1/33		210		242
#AL3455, 5.500%, due 11/1/33		3,164		3,678
#CA2754, 4.500%, due 11/1/33		539		590
#AL3401, 5.500%, due 2/1/34		617		717
#763798, 5.500%, due 3/1/34		38		44
#725228, 6.000%, due 3/1/34		1,993		2,336
#725611, 5.500%, due 6/1/34		47		54
#745563, 5.500%, due 8/1/34		268		310
#AL6413, 8.000%, due 8/1/34		234		268
#794474, 6.000%, due 10/1/34		24		28
#745092, 6.500%, due 7/1/35		148		170
#357944, 6.000%, due 9/1/35		7		8
#AL6412, 7.500%, due 9/1/35		393		450
#AD0979, 7.500%, due 10/1/35		28		33
#CA8368, 2.000%, due 12/1/35		4,744		4,924
#888305, 7.000%, due 3/1/36		5		5
#895637, 6.500%, due 5/1/36		25		30
#831540, 6.000%, due 6/1/36		11		13
#893318, 6.500%, due 8/1/36		7		8
#902974, 6.000%, due 12/1/36		91		108
#831926, 6.000%, due 12/1/36		329		390
#AB0265, 6.000%, due 2/1/37		6,079		7,251
#938440, 6.000%, due 7/1/37		49		58
#948689, 6.000%, due 8/1/37		64		74
#AL6411, 7.000%, due 12/1/37		968		1,115
#AL0904, 5.500%, due 1/1/38		55		63
#986856, 6.500%, due 9/1/38		48		56
#FM1735, 6.500%, due 10/1/38		3,686		4,510
#991911, 7.000%, due 11/1/38		71		80
#995076, 6.000%, due 11/1/38		2,808		3,364
#AD0752, 7.000%, due 1/1/39		311		386
#FM2467, 6.000%, due 1/1/39		3,439		4,127
#AC1619, 5.500%, due 8/1/39		162		188
#FM1736, 6.500%, due 10/1/39		5,937		7,155
#BM5204, 6.500%, due 6/1/40		3,623		4,350
#AD7137, 5.500%, due 7/1/40		2,130		2,483
#BM1689, 5.500%, due 8/1/40		1,710		1,980
#AL5815, 5.500%, due 4/1/41		2,071		2,410
#BM3525, 6.000%, due 4/1/41		7,597		9,031
#AL9226, 5.500%, due 12/1/41		8,772		10,308
#AL9225, 6.000%, due 1/1/42		3,886		4,620
#BM5121, 5.500%, due 12/1/48		8,793		10,499
Total FNMA Mortgage Obligations				93,847

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Bond Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Asset-Backed Securities—2.1%
Automobile—2.1%
Carmax Auto Owner Trust, 2021-1, Tranche D, 1.280%, 7/15/27	$	500	$	498
GM Financial Automobile Leasing Trust, 2020-1, Tranche D, 2.280%, 6/20/24		3,050		3,107
Tesla Auto Lease Trust—144A, 2019-A, Tranche E, 5.480%, 5/22/23		1,650		1,732
Tesla Auto Lease Trust—144A, 2019-A, Tranche D, 3.370%, 1/20/23		1,750		1,809
Total Automobile				7,146
Total Asset-Backed Securities				7,146

*Corporate Obligations—45.5%*
Financials—8.8%
Banco Inbursa S.A. Institucion de Banca Multiple—144A, 4.125%, due 6/6/24		2,000		2,135
Bank of America Corporation, 5.875%, due 2/7/42		2,000		2,878
Boston Properties L.P., 2.550%, due 4/1/32		3,200		3,227
Citigroup, Inc., 5.875%, due 1/30/42		2,000		2,885
ERP Operating L.P., 4.500%, due 6/1/45		2,500		3,138
Itau Unibanco Holding S.A.—144A, 5 year CMT + 3.446%, 3.875%, due 4/15/31, VRN		1,250		1,239
JPMorgan Chase & Co., SOFR + 3.125%, 4.600%, due 2/1/25, VRN		3,000		3,113
Royal Bank of Canada, SOFR + 0.525%, 0.548%, due 1/20/26, VRN		3,100		3,110
Simon Property Group L.P., 3.300%, due 1/15/26		2,750		2,994
The Bank of Nova Scotia, SOFR + 0.545%, 0.587%, due 3/2/26, VRN		3,100		3,105
Wells Fargo & Co., 4.480%, due 1/16/24		1,500		1,642
Total Financial				29,466
Communication Services—6.9%
Activision Blizzard, Inc., 2.500%, due 9/15/50		2,600		2,342
Alphabet, Inc., 1.100%, due 8/15/30		2,620		2,492
Amazon.com, Inc., 2.700%, due 6/3/60		2,500		2,404
AT&T, Inc., SOFR + 0.640%, 0.690%, due 3/25/24, VRN		750		752
AT&T, Inc., 5.700%, due 3/1/57		2,400		3,378


Issuer	Principal Amount		Value

Corporate Obligations—(continued)
Communication Services—(continued)
Comcast Corporation, 4.950%, due 10/15/58	$	2,000	$	2,778
Motorola Solutions, Inc., 4.600%, due 2/23/28		2,750		3,211
Omnicom Group, Inc., 2.450%, due 4/30/30		2,800		2,852
Verizon Communications, Inc., SOFR + 0.790%, 0.840%, due 3/20/26, VRN		3,000		3,057
Total Communication Services				23,266
Information Technology—6.2%
Apple, Inc., 4.650%, due 2/23/46		2,250		3,001
Booz Allen Hamilton, Inc.—144A, 4.000%, due 7/1/29		100		102
Corning, Inc., 5.850%, due 11/15/68		2,150		3,157
FLIR Systems, Inc., 2.500%, due 8/1/30		2,500		2,525
HP, Inc.—144A, 1.450%, due 6/17/26		325		323
HP, Inc.—144A, 2.650%, due 6/17/31		1,850		1,858
Intuit, Inc., 1.650%, due 7/15/30		1,200		1,182
Microsoft Corporation, 3.041%, due 3/17/62		2,032		2,188
Oracle Corporation, 3.950%, due 3/25/51		3,250		3,562
Roper Technologies, Inc., 4.200%, due 9/15/28		2,500		2,876
Total InformationTechnology				20,774
Consumer Discretionary—5.5%
Costco Wholesale Corporation, 1.750%, due 4/20/32		2,500		2,468
Dana, Inc., 4.250%, due 9/1/30		500		515
Ford Motor Co., 9.000%, due 4/22/25		500		617
Ford Motor Credit Co. LLC, 3M USD LIBOR + 1.235%, 1.391%, due 2/15/23, VRN		700		697
General Motors Financial Co., Inc., SOFR + 0.760%, 0.804%, due 3/8/24, VRN		1,475		1,486
Las Vegas Sands Corporation, 3.900%, due 8/8/29		1,600		1,706
Lennar Corporation, 4.500%, due 4/30/24		2,450		2,683
Meritage Homes Corporation, 5.125%, due 6/6/27		1,500		1,681
The Goodyear Tire & Rubber Co., 5.250%, due 4/30/31		2,000		2,090
Toll Brothers Finance Corporation, 4.375%, due 4/15/23		1,250		1,306

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Bond Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

*Corporate Obligations—(continued)*
Consumer Discretionary—(continued)
Toll Brothers Finance Corporation, 3.800%, due 11/1/29	$	1,500	$	1,611
Yum! Brands, Inc., 6.875%, due 11/15/37		1,250		1,557
Total Consumer Discretionary				18,417
Industrials—5.1%
ACCO Brands Corp.—144A, 4.250%, due 3/15/29		2,000		1,982
Caterpillar Financial Services Corporation, SOFR + 0.245%, 0.280%, due 5/17/24, VRN		2,025		2,028
CNH Industrial Capital LLC, 1.950%, due 7/2/23		2,500		2,563
Johnson Controls International plc, 1.750%, due 9/15/30		2,100		2,021
Owens Corning, 7.000%, due 12/1/36		2,250		3,277
Republic Services, Inc., 2.900%, due 7/1/26		2,500		2,681
Xylem, Inc., 3.250%, due 11/1/26		2,225		2,440
Total Industrial				16,992
Consumer Staples—4.6%
Altria Group, Inc., 6.200%, due 2/14/59		2,250		2,920
Fresenius Medical Care U.S. Finance III, Inc.—144A, 2.375%, due 2/16/31		1,800		1,761
Grupo Bimbo S.A.B. de C.V.—144A, 3.875%, due 6/27/24		2,000		2,153
PepsiCo, Inc., 4.450%, due 4/14/46		2,250		2,910
The Kroger Co., 8.000%, due 9/15/29		2,000		2,828
TreeHouse Foods, Inc., 4.000%, due 9/1/28		1,400		1,391
United Rentals North America, Inc., 5.250%, due 1/15/30		1,250		1,371
Total Consumer Staples				15,334
Real Estate—2.5%
American Tower Corporation, 4.000%, due 6/1/25		2,500		2,757
Jones Lang LaSalle, Inc., 4.400%, due 11/15/22		2,500		2,601
Public Storage, 1.850%, due 5/1/28		3,100		3,129
Total Real Estate				8,487
Health Care—2.3%
Abbott Laboratories, 1.400%, due 6/30/30		2,000		1,936
AbbVie, Inc., 4.700%, due 5/14/45		2,250		2,816
Centene Corporation, 2.450%, due 7/15/28		1,300		1,319


Issuer	Principal Amount			Value

Corporate Obligations—(continued)
Health Care—(continued)
Gilead Sciences, Inc., 1.200%, due 10/1/27	$	1,600		$	1,562
Total Health Care					7,633
Materials—1.5%
Orbia Advance Corp S.A.B. de C.V.—144A, 5.875%, due 9/17/44		2,250			2,721
Suzano Austria GmbH, 3.125%, due 1/15/32		2,420			2,397
Total Materials					5,118
Energy—1.4%
ConocoPhillips, 6.500%, due 2/1/39		2,000			2,975
S.A. Global Sukuk Ltd.—144A, 2.694%, due 6/17/31		1,800			1,817
Total Energy					4,792
Utilities—0.7%
NextEra Energy Capital Holdings, Inc., 1.900%, due 6/15/28		2,400			2,425
Total Corporate Obligations					152,704
Total Long-Term Investments—99.5% (cost $317,820)					333,752
Repurchase Agreement—0.1%
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $291, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $297		291			291
Total Repurchase Agreement—0.1% (cost $291)					291
Commercial Paper—0.3%
Sonoco Product Co., 0.102%, due 7/1/21		1,100			1,100
Total Commercial Paper—0.3% (cost $1,100)					1,100
Total Investments—99.9% (cost $319,211)					335,143

*Securities Sold , Not Yet Purchased*

*U.S. Government Agency—(1.6)%*
Federal National Mortgage Association (FNMA)—(1.6)%
TBA, 4.000%, due 7/1/51		(5,000	)		(5,326	)
Total Securities Sold, Not Yet Purchased—(1.6)% (proceeds $5,350)					(5,326	)
Cash and other assets, less liabilities—1.7%					5,614
Net assets—100.0%				$	335,431

See accompanying Notes to Financial Statements.

June 30, 20201

William Blair Funds

Bond Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)

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.

SOFR = Secured Overnight Financing Rate

TBA = To Be Announced—TBAs are mortgage-backed securities traded under delayed delivery commitments, settling after June 30, 2021. 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

(a) Security, or a portion of security, is segregated as collateral for the centrally cleared credit default swaps, aggregating a total of $1,086 (in thousands).

(b) Amount is less than the minimum amount disclosed.

Centrally Cleared Credit Default Swaps

Reference Entity	Buy/Sell Protection	Fixed Rate	Payment Frequency	Maturity Date	Cleared Exchange	Notional Amount (in thousands)	Upfront Payment Paid (Received)	Value	Unrealized Appreciation (Depreciation)
CDX.NA.HY- 34	Buy	5.000%	3M	June 2025	ICE	$ 9,200	$(907)	$(922)		$	(15)
CDX.NA.HY- 35	Buy	5.000%	3M	December 2025	ICE	5,000	(501)	(513)			(12)
CDX.NA.IG- 35	Buy	1.000%	3M	December 2030	ICE	15,000	(186)	(201)			(15)
Total net unrealized appreciation (depreciation) on swaps										$	(42)

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

	Income Fund

	The Income Fund seeks a high level of current income with relative stability of principal.

	AN OVERVIEW FROM THE PORTFOLIO MANAGER

Ruta Ziverte	The William Blair Income Fund (Class N shares) (the “Fund”) returned a 0.83% decrease, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the Bloomberg Barclays Intermediate Government/Credit Bond Index (the “Index”), decreased 0.90%. The Fund outperformed the Index on a relative basis in the first half of the year as sector allocation, security selection, and interest rate positioning drove excess returns, which offset the negative performance impact of rising yields in the first quarter. The yield curve steepened in the period as longer-term yields rose while front-end (under two years maturity) yields declined modestly. Our underweight to U.S. Treasuries, driven by valuations, was the largest contributor to relative performance. Within the Treasury sector we opted to use a portion of our allocation to invest in inflation-linked U.S. Treasury Inflation-Protected Securities as they looked attractive versus nominal Treasuries as inflation expectations rose in the period. Conversely, security selection within investment grade corporate exposure detracted from performance as Fund holdings emphasized higher-quality, more defensive companies. This was more than offset, however, by rate positioning within the sector. During the period lower-quality debt outperformed higher-quality debt and the strategy’s 10% limit on BBB-rated debt was a relative detractor. From an attribution perspective, interest rate impacts within the Fund’s agency mortgage-backed securities holdings detracted from relative performance. The use of credit default swap index hedging, used to reduce credit exposure at the margin, detracted from performance as credit spreads tightened in the period. Please refer to the Fixed Income Market Review and Outlook relating to the Fund on page 72.

June 30, 2021

William Blair Funds

Income Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year			Since Inception(a)
Class N		(0.83	)%		0.33	%		3.19	%		1.87	%		2.27	%		—	%
Class I		(0.76	)		0.36			3.36			2.05			2.48			—
Class R6		(0.73	)		0.41			—			—			—			3.16
Bloomberg Barclays Intermediate Government/Credit Bond Index		(0.90	)		0.19			4.70			2.63			2.76			4.48

(a)	Since inception is for the period from May 2, 2019 (Commencement of Operations) to June 30, 2021.

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.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

Semiannual Report

June 30, 2021

Income Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

U.S. Government and U.S. Government Agency—47.4%
U.S. Treasury Inflation Indexed Notes/Bonds—5.0%
U.S. Treasury Inflation Indexed Bond, 2.375%, due 1/15/27	$	331	$	406
U.S. Treasury Inflation Indexed Bond, 3.875%, due 4/15/29		1,462		2,058
U.S. Treasury Inflation Indexed Bond, 3.375%, due 4/15/32		90		133
Total U.S. Treasury Inflation Indexed Notes/Bonds				2,597
U.S. Treasury—7.2%
U.S. Treasury Note, 0.350%, due 10/31/21		450		450
U.S. Treasury Note, 2.500%, due 2/15/22^(a)		470		477
U.S. Treasury Note, 0.099%, due 1/31/23		500		500
U.S. Treasury Note, 0.250%, due 7/31/25		1,000		982
U.S. Treasury Note, 1.125%, due 2/28/27		600		605
U.S. Treasury Strip Principal, 0.000%, due 8/15/27		775		726
Total U.S. Treasury				3,740
Federal Home Loan Mortgage Corp. (FHLMC)—7.3%
#J13022, 4.000%, due 9/1/25		126		135
#G14150, 4.500%, due 4/1/26		38		40
#J16051, 4.500%, due 7/1/26		312		334
#G15030, 4.000%, due 3/1/29		232		251
#A17603, 5.500%, due 1/1/34		320		372
#G01705, 5.500%, due 6/1/34		578		674
#A45790, 7.500%, due 5/1/35		58		66
#G04126, 6.000%, due 6/1/37		131		156
#G04564, 6.000%, due 12/1/37		101		120
#G05566, 5.500%, due 12/1/38		74		86
#G05875, 5.500%, due 2/1/40		50		59
#G61450, 6.000%, due 4/1/40		1,191		1,426
#C03665, 9.000%, due 4/1/41		80		97
Total FHLMC Mortgage Obligations				3,816
Federal National Mortgage Association (FNMA)—27.9%
FNR G93-19 SH, 1M USD LIBOR + 56.169%, 11.234%, due 4/25/23, VRN		4		4
#255956, 5.500%, due 10/1/25		13		14
#AL2853, 4.500%, due 6/1/26		201		211
#AJ6954, 4.000%, due 11/1/26		65		70
#256639, 5.000%, due 2/1/27		3		4
#806458, 8.000%, due 6/1/28		54		60
#880155, 8.500%, due 7/1/29		85		96
#745519, 8.500%, due 5/1/32		38		41
#654674, 6.500%, due 9/1/32		25		29
#AD0725, 7.000%, due 12/1/32		404		482
#254693, 5.500%, due 4/1/33		3		4
#555531, 5.500%, due 6/1/33		29		33
#711736, 5.500%, due 6/1/33		47		54
#555591, 5.500%, due 7/1/33		5		6
#AL3455, 5.500%, due 11/1/33		929		1,080
#CA2754, 4.500%, due 11/1/33		—		—	^(b)
#725424, 5.500%, due 4/1/34		31		36
#AL6413, 8.000%, due 8/1/34		114		131


Issuer	Principal Amount		Value

U.S. Government and U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#AL6412, 7.500%, due 9/1/35	$	295	$	338
#888884, 5.500%, due 12/1/35		73		84
#928658, 6.500%, due 9/1/37		12		14
#889371, 6.000%, due 1/1/38		1,357		1,613
#FM1735, 6.500%, due 10/1/38		1,043		1,276
#995076, 6.000%, due 11/1/38		374		449
#991911, 7.000%, due 11/1/38		45		51
#FM2467, 6.000%, due 1/1/39		382		459
#FM1736, 6.500%, due 10/1/39		982		1,184
#BM5204, 6.500%, due 6/1/40		106		127
#BM1689, 5.500%, due 8/1/40		231		267
#AL9226, 5.500%, due 12/1/41		1,655		1,945
#AL9225, 6.000%, due 1/1/42		1,069		1,270
#BM1328, 6.000%, due 1/1/42		1,157		1,380
#BM5121, 5.500%, due 12/1/48		1,446		1,726
Total FNMA Mortgage Obligations				14,538

Asset-Backed Securities—5.3%
Automobile—2.9%
Carmax Auto Owner Trust, 2021-1, Tranche C, 0.940%, 12/15/26		550		548
GM Financial Automobile Leasing Trust, 2020-1, Tranche C, 2.040%, 12/20/23		950		966
Total Automobile				1,514
Credit Card—1.6%
Citibank Credit Card Issuance Trust, 2016-A3, Tranche A3, 1M USD LIBOR + 0.490%, 0.570%, 12/7/23, VRN		800		802
Other—0.8%
Verizon Owner Trust, 2020-A, Tranche C,2.060%, 7/22/24		425		436
Total Asset-Backed Securities				2,752

Corporate Obligations—46.6%
Financials—20.3%
Bank of America Corporation, SOFR + 0.910%, 0.981%, due 9/25/25, VRN		700		700
Bank of Montreal, SOFR + 0.680%, 0.726%, due 3/10/23, VRN		600		605
Brookfield Finance, Inc., 4.250%, due 6/2/26		550		619
Canadian Imperial Bank of Commerce, SOFR + 0.800%, 0.850%, due 3/17/23, VRN		750		756
Capital One Financial Corporation, 4.200%, due 10/29/25		500		559
Citigroup, Inc., SOFR + 0.770%, 0.817%, due 6/9/27, VRN		625		626

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Income Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Corporate Obligations—(continued)
Financials—(continued)
Intercontinental Exchange, Inc., 3.750%, due 12/1/25	$	450	$	499
JPMorgan Chase & Co., SOFR + 3.125%, 4.600%, due 2/1/25, VRN		450		467
KeyBank NA, SOFR + 0.340%, 0.390%, due 1/3/24, VRN		700		701
Morgan Stanley, SOFR + 0.745%, 0.864%, due 10/21/25, VRN		550		550
New York Life Global Funding—144A, SOFR + 0.480%, 0.526%, due 6/9/26, VRN		600		601
Royal Bank of Canada, SOFR + 0.450%, 0.475%, due 10/26/23, VRN		350		352
Simon Property Group L.P., 3.300%, due 1/15/26		550		599
Skandinaviska Enskilda Banken AB—144A, 0.850%, due 9/2/25		500		495
The Bank of Nova Scotia, SOFR + 0.545%, 0.587%, due 3/2/26, VRN		675		676
The Charles Schwab Corporation, SOFR + 0.520%, 0.554%, due 5/13/26, VRN		470		472
The Goldman Sachs Group, Inc., SOFR + 0.810%, 0.856%, due 3/9/27, VRN		600		600
Wells Fargo & Co., 4.480%, due 1/16/24		650		711
Total Financials				10,588
Communication Services—5.6%
Amazon.com, Inc., 1.500%, due 6/3/30		450		442
AT&T, Inc., 4.125%, due 2/17/26		400		450
Comcast Corporation, 3.950%, due 10/15/25		600		673
Tencent Holdings Ltd.—144A, 1.810%, due 1/26/26		700		711
Verizon Communications, Inc., SOFR + 0.790%, 0.840%, due 3/20/26, VRN		600		611
Total Communication Services				2,887
Consumer Discretionary—4.8%
American Honda Finance Corporation, 1.200%, due 7/8/25		450		454
BMW US Capital LLC Co.—144A, SOFR + 0.530%, 0.580%, due 4/1/24, VRN		110		111
Costco Wholesale Corporation, 1.375%, due 6/20/27		500		504


Issuer	Principal Amount			Value

Corporate Obligations—(continued)
Consumer Discretionary—(continued)
General Motors Financial Co., Inc., SOFR + 0.760%, 0.804%, due 3/8/24, VRN	$	500	��	$	504
Toll Brothers Finance Corporation, 3.800%, due 11/1/29		250			268
Toyota Motor Credit Corporation, SOFR + 0.330%, 0.349%, due 1/11/24, VRN		650			652
Total Consumer Discretionary					2,493
Consumer Staples—2.0%
The Hershey Co., 0.900%, due 6/1/25		525			527
The Kroger Co., 8.000%, due 9/15/29		350			495
Total Consumer Staples					1,022
Industrials—2.9%
Caterpillar Financial Services Corporation, SOFR + 0.245%, 0.280%, due 5/17/24, VRN		600			601
Johnson Controls International plc, 1.750%, due 9/15/30		350			337
United Parcel Service, Inc., 3.900%, due 4/1/25		500			554
Total Industrials					1,492
Information Technology—2.8%
HP, Inc.—144A, 1.450%, due 6/17/26		600			597
Intuit, Inc., 0.950%, due 7/15/25		450			452
Roper Technologies, Inc., 4.200%, due 9/15/28		375			431
Total Information Technology					1,480
Energy—2.6%
ConocoPhillips Co., 4.950%, due 3/15/26		600			698
S.A. Global Sukuk Ltd.—144A, 1.602%, due 6/17/26		175			175
Shell International Finance BV, 0.375%, due 9/15/23		500			500
Total Energy					1,373
Health Care —4.2%
Abbott Laboratories, 1.150%, due 1/30/28		600			588
Centene Corporation, 2.450%, due 7/15/28		200			203
Gilead Sciences, Inc., 1.200%, due 10/1/27		400			390
GlaxoSmithKline Capital plc, 0.534%, due 10/1/23		300			300
Merck & Co., Inc., 0.750%, due 2/24/26		700			697
Total Health Care					2,178

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Income Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount			Value

Corporate Obligations—(continued)
Materials—1.1%
Fibria Overseas Finance, Ltd., 5.500%, due 1/17/27	$	500		$	580
Real Estate—0.3%
Public Storage, SOFR + 0.470%, 0.495%, due 4/23/24, VRN		175			175
Total Corporate Obligations					24,268
Total Long-Term Investments—99.3% (cost $50,609)					51,711

Repurchase Agreement
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $149, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $152		149			149
Total Repurchase Agreement—0.3% (cost $149)					149
Total Investments—99.6% (cost $50,758)					51,860

Securities Sold, Not Yet Purchased

U.S. Government Agency—(2.0)%
Federal National Mortgage Association (FNMA)—(2.0)%
TBA, 4.000%, due 7/1/51		(1,000	)		(1,065	)
Total Securities Sold, Not Yet Purchased—(2.0)% (proceeds $1,070)					(1,065	)
Cash and other assets, less liabilities—2.4%					1,254
Net assets—100.0%				$	52,049

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

SOFR = Secured Overnight Financing Rate

VRN = Variable Rate Note

(a) Security, or a portion of security, is segregated as collateral for the centrally cleared credit default swap, aggregating a total of $214 (in thousands).

(b) Amount is less than the minimum amount disclosed.

Centrally Cleared Credit Default Swap

Reference
Entity

Buy/Sell
Protection

Fixed
Rate

Payment
Frequency

Maturity
Date

Cleared
Exchange

Notional
Amount
(in thousands)

Upfront
Payment
Paid
(Received)

Value

Unrealized
Appreciation
(Depreciation)

CDX.NA.HY- 34

Buy

5.000%

June 2025

ICE

$4,600

$(454)

$(462)

$(8)

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	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

Kathleen M. Lynch, CFA Vesta Marks, CFA, CAIA Ruta Ziverte	The William Blair Low Duration Fund (Class N shares) (the “Fund”) returned 0.05%, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the ICE BofAML 1-Year US Treasury Note Index (the “Index”), returned 0.09%. Relative performance was driven by coupon income, which offset the negative impact of paydowns. Specifically, income from the Fund’s holdings of agency mortgage-backed securities (“MBS”), investment grade corporates, and asset-backed securities sectors drove absolute and relative performance in the first half. The use of floating rate securities also contributed to relative performance as they outperformed fixed-rate securities in the period. Conversely, the Fund’s underweight position in the U.S. Treasury sector detracted from relative performance. The Index uses a single Treasury security to represent market performance of the risk-free rate. From an attribution perspective, paydown and price impacts in the agency MBS sector was a relative detractor in the period. However, in total, this sector was a contributor to absolute and relative performance given the income earned. Please refer to the Fixed Income Market Review and Outlook relating to the Fund on page 72.

Semiannual Report

June 30, 2021

Low Duration Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			10 Year
Class N		0.05	%		0.74	%		2.19	%		1.54	%		1.28	%
Class I		0.12			0.90			2.35			1.70			1.44
Class R6		0.15			0.94			2.39			1.75			1.51
ICE BofAML 1-Year US Treasury Note Index		0.09			0.22			2.01			1.47			0.90

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 ICE BofAML 1-Year US 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.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

June 30, 2021

William Blair Funds

Low Duration Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

U.S. Government and U.S. Government Agency—51.6%
U.S. Treasury—7.0%
U.S. Treasury Note, 2.500%, due 1/15/22	$	2,300	$	2,330
U.S. Treasury Note, 0.204%, due 1/31/22		2,000		2,002
U.S. Treasury Note, 0.164%, due 4/30/22		2,500		2,502
U.S. Treasury Strip Principal, 0.000%, due 8/15/21		3,000		3,000
Total U.S. Treasury				9,834
Federal Home Loan Mortgage Corp. (FHLMC)—10.8%
#E02322, 5.500%, due 5/1/22		2		2
#G12725, 6.000%, due 6/1/22		8		8
#G13225, 5.000%, due 6/1/23		253		264
#J08450, 5.500%, due 7/1/23		4		4
#J08703, 5.500%, due 9/1/23		3		3
#C00351, 8.000%, due 7/1/24		14		14
#J11208, 5.000%, due 11/1/24		12		12
#G00363, 8.000%, due 6/1/25		23		24
#C80329, 8.000%, due 8/1/25		4		5
#G14643, 4.000%, due 8/1/26		61		65
#G14550, 4.500%, due 9/1/26		353		372
#G15360, 4.500%, due 11/1/26		139		148
#G04821, 8.500%, due 7/1/31		1,027		1,250
#G02454, 6.500%, due 7/1/32		441		504
#ZT1221, 5.500%, due 1/1/33		417		481
#A81372, 6.000%, due 8/1/38		123		143
#G04745, 6.000%, due 9/1/38		121		139
#G04687, 6.000%, due 9/1/38		31		36
#G06085, 6.500%, due 9/1/38		30		36
#G60681, 7.000%, due 2/1/39		4,230		5,156
#G07480, 6.000%, due 5/1/39		539		638
#G07058, 6.000%, due 9/1/39		548		669
#G60680, 6.500%, due 9/1/39		516		619
#G61450, 6.000%, due 4/1/40		3,572		4,277
#G61050, 5.500%, due 3/1/41		247		289
Total FHLMC Mortgage Obligations				15,158
Federal National Mortgage Association (FNMA)—33.8%
#323933, 7.000%, due 9/1/29		194		225
#880993, 6.000%, due 1/1/22		—		—	^(a)
#888982, 6.000%, due 12/1/22		12		12
#972934, 5.500%, due 2/1/23		14		14
#889670, 5.500%, due 6/1/23		3		3
#AE0011, 5.500%, due 9/1/23		2		1
#995253, 5.500%, due 12/1/23		103		105
#995395, 6.000%, due 12/1/23		5		5
#190988, 9.000%, due 6/1/24		1		1
#AL8529, 6.000%, due 11/1/24		1,477		1,536
#AL2853, 4.500%, due 6/1/26		636		670
#AL9730, 4.500%, due 2/1/27		1,108		1,178
#AL3388, 4.000%, due 9/1/27		235		250
#AL9870, 6.500%, due 2/1/28		520		584
#AL4502, 4.000%, due 11/1/28		391		423


Issuer	Principal Amount		Value

U.S. Government and U.S. Government Agency—(continued)
Federal National Mortgage Association (FNMA)—(continued)
#AL9857, 4.000%, due 2/1/29	$	3,002	$	3,200
#555933, 7.000%, due 6/1/32		259		293
#555866, 7.500%, due 3/1/33		148		172
#745409, 7.000%, due 4/1/33		352		397
#CA2408, 4.000%, due 10/1/33		137		150
#CA2754, 4.500%, due 11/1/33		88		97
#725228, 6.000%, due 3/1/34		639		749
#AL6413, 8.000%, due 8/1/34		133		152
#AD0720, 5.500%, due 12/1/34		177		204
#CA5298, 4.000%, due 2/1/35		3,849		4,238
#AL6412, 7.500%, due 9/1/35		492		563
#CA8368, 2.000%, due 12/1/35		—		—	^(a)
#886762, 7.000%, due 9/1/36		156		187
#AD0731, 7.500%, due 8/1/37		3,619		4,358
#888530, 7.500%, due 8/1/37		1,367		1,720
#AL6411, 7.000%, due 12/1/37		968		1,115
#889219, 6.000%, due 3/1/38		930		1,144
#FM1735, 6.500%, due 10/1/38		1,862		2,278
#995076, 6.000%, due 11/1/38		1,708		2,047
#AD0100, 7.000%, due 12/1/38		374		447
#FM2467, 6.000%, due 1/1/39		1,529		1,834
#FM1736, 6.500%, due 10/1/39		2,372		2,859
#BM5204, 6.500%, due 6/1/40		2,053		2,465
#AL0515, 6.000%, due 7/1/40		414		503
#BM3525, 6.000%, due 4/1/41		2,157		2,564
#AL9226, 5.500%, due 12/1/41		2,234		2,625
#BM1328, 6.000%, due 1/1/42		1,113		1,327
#AL9225, 6.000%, due 1/1/42		1,749		2,079
#AL6276, 5.500%, due 10/1/43		133		154
#BM5121, 5.500%, due 12/1/48		954		1,139
#CA5837, 6.000%, due 7/1/49		1,273		1,524
Total FNMA Mortgage Obligations				47,591

Asset-Backed Securities—11.2%
Automobile—5.9%
CarMax Auto Owner Trust, 2020-1, Tranche C, 2.340%, 11/17/25		600		620
Ford Credit Auto Lease Trust 2019-B, 2019-B, Tranche A4, 2.270%, 11/15/22		329		332
GM Financial Automobile Leasing Trust, 2019-2, Tranche C, 3.120%, 3/20/23		500		505
GM Financial Automobile Leasing Trust, 2020-1, Tranche C, 2.040%, 12/20/23		1,400		1,423
GM Financial Consumer Automobile Receivables Trust, 2018-4, Tranche A3, 3.210%, 10/16/23		328		332
Mercedes-Benz Auto Lease Trust 2020-B, 2020-B, Tranche A2, 0.310%, 2/15/23		355		356

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Low Duration Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Asset-Backed Securities—(continued)
Automobile—(continued)
Nissan Auto Lease Trust 2020-B, 2020-B, Tranche A3, 0.430%, 10/16/23	$	550	$	551
Nissan Auto Receivables 2020-A Owner Trust, 2020-A, Tranche A3, 1.380%, 12/16/24		1,126		1,140
Tesla Auto Lease Trust 2018-B—144A, 2018-B, Tranche A, 3.710%, 8/20/21		4		4
Tesla Auto Lease Trust—144A, 2019-A, Tranche C, 2.680%, 1/20/23		675		691
Toyota Auto Receivables 2020-B Owner Trust, 2020-B, Tranche A2, 1.380%, 12/15/22		434		435
Toyota Auto Receivables 2021-B Owner Trust, 2021-B, Tranche A2, 0.140%, 1/16/24		1,900		1,900
Total Automobile				8,289
Credit Card—2.2%
American Express Credit Account Master Trust, 2017-5, Tranche B, 1M USD LIBOR + 0.580%, 0.653%, 2/18/25, VRN		450		452
Chase Issuance Trust, 2017-A2, Tranche A, 1M USD LIBOR + 0.400%, 0.473%, 3/15/24, VRN		1,545		1,551
Citibank Credit Card Issuance Trust, 2016-A3, Tranche A3, 1M USD LIBOR + 0.490%, 0.570%, 12/7/23, VRN		1,150		1,153
Total Credit Card				3,156
Other—3.1%
CNH Equipment Trust 2020-A, 2020-A, Tranche A3, 1.160%, 6/16/25		300		303
Kubota Credit Owner Trust—144A, 2020-2A, Tranche A2, 0.410%, 6/15/23		1,167		1,168
PFS Financing Corp.—144A, 2018-F, Tranche B, 3.770%, 10/15/23		1,000		1,010
Verizon Owner Trust, 2020-A, Tranche C, 2.060%, 7/22/24		1,250		1,282
Verizon Owner Trust 2018-A, 2018-A, Tranche A1A, 3.230%, 4/20/23		520		524
Verizon Owner Trust 2019-C, 2019-C, Tranche C, 2.160%, 4/22/24		60		62
Total Other				4,349
Total Asset-Backed Securities				15,794


Issuer	Principal Amount		Value

Corporate Obligations—36.7%
Financials—27.9%
Bank of America Corporation, SOFR + 0.970%, 0.995%, due 7/22/27, VRN	$	2,850	$	2,894
Bank of Montreal, SOFR + 0.680%, 0.726%, due 3/10/23, VRN		2,700		2,722
Canadian Imperial Bank of Commerce, SOFR + 0.800%, 0.850%, due 3/17/23, VRN		1,000		1,009
Canadian Imperial Bank of Commerce, SOFR + 0.400%, 0.447%, due 12/14/23, VRN		1,900		1,903
Citigroup, Inc., SOFR + 0.770%, 0.817%, due 6/9/27, VRN		2,750		2,754
JPMorgan Chase & Co., SOFR + 0.885%, 0.910%, due 4/22/27, VRN		2,750		2,785
KeyBank NA, SOFR + 0.340%, 0.390%, due 1/3/24, VRN		2,700		2,703
Met Tower Global Funding—144A, SOFR + 0.550%, 0.572%, due 1/17/23, VRN		1,481		1,490
Metropolitan Life Global Funding I—144A, SOFR + 0.320%, 0.337%, due 1/7/24, VRN		1,500		1,505
Morgan Stanley, SOFR + 0.700%, 0.725%, due 1/20/23, VRN		2,750		2,760
New York Life Global Funding—144A, SOFR + 0.480%, 0.526%, due 6/9/26, VRN		2,750		2,754
Royal Bank of Canada, SOFR + 0.450%, 0.475%, due 10/26/23, VRN		1,500		1,507
Royal Bank of Canada, SOFR + 0.525%, 0.548%, due 1/20/26, VRN		1,500		1,505
The Bank of Nova Scotia, SOFR + 0.550%, 0.598%, due 9/15/23, VRN		2,000		2,014
The Bank of Nova Scotia, SOFR + 0.545%, 0.587%, due 3/2/26, VRN		980		982
The Charles Schwab Corporation, SOFR + 0.520%, 0.554%, due 5/13/26, VRN		2,500		2,513
The Goldman Sachs Group, Inc., SOFR + 0.810%, 0.856%, due 3/9/27, VRN		2,750		2,749
The Toronto-Dominion Bank, SOFR + 0.355%, 0.399%, due 3/4/24, VRN		2,700		2,707
Total Financials				39,256

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Low Duration Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Corporate Obligations—(continued)
Consumer Discretionary —2.4%
BMW US Capital LLC Co.—144A, SOFR + 0.530%, 0.580%, due 4/1/24, VRN	$	500	$	504
Toyota Motor Credit Corporation, SOFR + 0.330%, 0.349%, due 1/11/24, VRN		2,800		2,810
Total Consumer Discretionary				3,314
Communication Services—2.1%
Verizon Communications, Inc., SOFR + 0.790%, 0.840%, due 3/20/26, VRN		2,900		2,955
Industrials—2.0%
Caterpillar Financial Services Corporation, SOFR + 0.245%, 0.280%, due 5/17/24, VRN		2,750		2,754
Real Estate—1.4%
Public Storage, SOFR + 0.470%, 0.495%, due 4/23/24, VRN		2,005		2,009
Health Care—0.9%
Roche Holdings, Inc.—144A, SOFR + 0.240%, 0.284%, due 3/5/24, VRN		1,275		1,277
Total Corporate Obligations				51,565
Total Long-Term Investments—99.5% (cost $139,422)				139,942
Total Investments—99.5% (cost $139,422)				139,942


Issuer	Principal Amount			Value

Securities Sold, Not Yet Purchased U.S. Government Agency—(15.0)%
Federal National Mortgage Association (FNMA)—(15.0)%
TBA, 2.500%, due 7/1/36	$	(10,000	)	$	(10,428	)
TBA, 4.000%, due 7/1/51		(10,000	)		(10,652	)
Total Securities Sold, Not Yet Purchased—(15.0)% (proceeds $21,129)					(21,080	)
Cash and other assets, less liabilities—15.5%					21,831
Net assets—100.0%				$	140,693

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

SOFR = Secured Overnight Financing Rate

VRN = Variable Rate Note

(a) Amount is less than the minimum amount disclosed.

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Debt Market Review and Outlook

Markets traded on a positive note throughout the second quarter of 2021 amid improved prospects for global economic activity as a growing number of economies continued to reopen, supported by falling COVID-19 cases and accelerating vaccination programs.

In the United States, where economic growth conditions have rebounded sharply versus those in 2020, the Federal Reserve continued to indicate the continuation of extraordinary monetary policy accommodation as concerns about rising inflationary pressures were mitigated by disappointing job creation. Overall, a positive combination of improving global growth and favorable liquidity conditions continued to support investor sentiment, leading to higher equity and commodity prices and tighter credit spreads during the period.

In this context, the credit spread of the J.P. Morgan Emerging Markets Bond Index Global Diversified (EMBIGD) ended the second quarter at 340 basis points (bps), compressing by 15 bps, with the index returning 4.06% in U.S. dollar terms during the period. The strong performance of the index was driven by high-yielding countries, where credit spreads compressed by 37 bps, on average.

We retain a constructive outlook for the asset class. We believe that a positive combination of improving global growth and favorable liquidity conditions will continue supporting investor sentiment throughout the third quarter of the year.

Across emerging markets (EMs), we believe credit fundamentals should continue to recover amid improving economic growth, rising global trade, and higher commodity prices. Moreover, prospects for a $650 billion increase in the International Monetary Fund’s Special Drawing Rights (SDR) allocation to EM countries underscore strong support from multilateral organizations.

While we believe U.S. Treasury yields should remain the main headwind for EM debt returns over the coming quarter, we see limited scope for a significant increase in yields. We anticipate the continuation of extraordinary monetary policy accommodation in the United States as concerns about rising inflationary pressures may be mitigated by disappointing job creation.

In our opinion, technical conditions should also remain supported by positive investor flows, contained new net debt issuance, and strong inflows from non-dedicated, crossover investors attracted by favorable valuations of EM debt relative to developed-market credit.

In our view, EM debt hard currency valuations remain attractive, especially in the high-yield space, where credit spreads remain above long-term averages. These valuations are particularly attractive relative to U.S. high-yield corporate credit. We believe the risk premia in EM debt hard currency sovereign credit overcompensate investors for default and loss-given-default risks.

In this overall context, we see prospects for EM debt risk premia compression, and we expect tighter credit spreads to partly offset marginally higher U.S. Treasury yields in the coming months.

We believe that improving credit fundamentals, ample liquidity conditions, positive investor flows, strong support from multilateral organizations, and attractive valuations should all underpin the performance of the asset class during the third quarter of the year.

June 30, 2021

William Blair Funds

	Emerging Markets Debt Fund

	The Emerging Markets Debt Fund seeks to provide attractive risk-adjusted returns relative to the Fund’s benchmark through investments in hard currency denominated debt issued in emerging market countries.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS

Marcelo Assalin, CFA Marco Ruijer, CFA	The William Blair Emerging Markets Debt Fund (Class I shares) posted a 0.37% increase, net of fees, for the period since inception (May 25, 2021) through June 30, 2021 (the “period”). By comparison, the Fund’s benchmark index, the JPMorgan Emerging Markets Bond Index (EMBI) Global Diversified (the “Index”), increased 0.92%. Higher-Risk Countries In higher-risk countries, our overweight positions in Ukraine, Cameroon and Ghana contributed the most to performance during the period, while our overweight positions in Sri Lanka, Lebanon and Egypt detracted the most. In Ukraine, while uncertainty remained about the timeline of further disbursements from the International Monetary Fund (IMF), our overweight position in warrants linked to gross domestic product (GDP) outperformed. This outperformance in Ukraine was driven by higher expectations for future payout ratios of the instrument amid growing prospects for economic improvement in the country. In Cameroon, our overweight position benefitted from an export boost driven by a surge in commodity prices and staff level agreement agreed at the end of May with the IMF. Through the result of a successful liability management exercise, Cameroon has not only eased its medium term amortization program but also reduced concerns that Cameroon would apply for debt relief under the common framework. In Ghana, bonds continue to perform well amid improving prospects for policy continuity under President Nana Akufo-Addo’s second term. Investors expect the ruling party to continue to seek fiscal prudence through a combination of revenue and expenditure measures. Our corporate exposure to an oil company operating in Ghana also added meaningfully to performance. In Sri Lanka, bond prices fell sharply during the period reversing stellar investor optimism throughout April and May. Fitch affirmed Sri Lanka’s external debt at a CCC rating citing concerns about a problematic medium-term debt repayment burden, low levels of FX reserves and rising government debt levels. Lebanon continued to underperform given the continued delay in the formation of a government. Lebanon also faced further headwinds as the number of COVID-19 infections surged during the festive season. The government has limited means to curb the deterioration of economic conditions. Lastly, in Egypt sentiment waned on the back of concerns that Egypt is unlikely to extend the IMF program which has been such a strong anchor for policy reform. These fears came on the back of weak balance of payments data for the first quarter which showed imports rising significantly. As Egypt is a favored overweight position for EMBI investors the impact has been more emphatic as positions were reduced during the period on these negative headlines. Medium-risk countries In medium-risk countries, overweight positions in Brazil, Dominican Republic and Bahrain contributed the most to performance during the period. Meanwhile, overweight positions in Paraguay, Senegal and Benin detracted the most.

Semiannual Report

June 30, 2021

Emerging Markets Debt Fund

Our diverse corporate positions continued to contribute to outperformance in Brazil through security selection in Brazil. Performance was led by investments in oil and gas, consumer, financials, and metals and mining. This was slightly offset by a new issue in transportation.

In the Dominican Republic, while we believe growth is picking up and there is renewed momentum in fiscal reform, inflation has spiked to the highest level in more than a decade. Moreover, although the country has one of the highest COVID-19 vaccination rates in the region at roughly 70% of the adult population, questions about the efficacy of the Sinovac vaccine have led to concerns about how vulnerable the country remains to the virus. Within corporates, we benefited from a position in a local utility. Security selection was the primary driver of outperformance in the Dominican Republic.

In Bahrain our overweight position added value as higher oil prices have improved market confidence that GCC support will be more forthcoming and will help to alleviate the fiscal burden following the announcement of an economic stimulus package designed to limit the impact of COVID-19.

In Senegal an announcement of delays to oil and gas production have increased fears that debt levels will continue to rise for longer whilst the market also had to absorb the issuance of a new 15-year euro denominated bond. Similarly, in Benin expectations of a new issue and the stronger performance of USD denominated bonds in Sub Saharan Africa held back the performance of our euro denominated holding.

Lower-risk countries

In lower-risk countries, overweight positions in India and Thailand contributed the most to performance, while overweight positions in Romania and Serbia and an underweight position in Peru detracted the most.

In India, where we maintained an overweight position mainly through corporates, performance was driven by security selection. A diversified commodity producer generated most of the outperformance in India. Positions in renewable energy, steel, and infrastructure also contributed, although this was marginally offset by quasi-sovereign credit exposures.

In Thailand, our position in a local bank underperformed amid local protests and worsening COVID-19 situation.

In Romania and Serbia, our holdings in euro-denominated bonds, which are more sensitive to German bunds than to U.S. Treasury price movement, underperformed as a retracement in U.S. yields was not matched by euro-denominated fixed income.

Lastly, Peru outperformed over the month of June, as the pessimism priced in by markets following recent Presidential elections was faded. Some ratings sensitive insurance companies bought bonds in the days after the election, despite the market unfriendly candidate winning the election, as they found valuations in Peruvian bonds to be attractive given its rating. Others pointed to signs of moderation from the Castillo administration such as Castillo asking Central Bank President Velarde to stay in his post as reasons to buy. We however remain skeptical about how moderate Castillo’s administration will be.

Please refer to the Emerging Markets Debt Market Review and Outlook relating to the Fund on page 89.

June 30, 2021

William Blair Funds

Emerging Markets Debt Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Since Inception(a)
Class I		0.37	%
Class R6		0.37
JPMorgan EMBI Global Diversified		0.92

(a)	Since inception is for the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

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 JP Morgan Emerging Markets Bond Index (EMBI) Global Diversified tracks the total return of U.S.-dollar denominated debt instruments issued by sovereign and quasi-sovereign entities.

Sector Diversification (Unaudited)

The sector diversification shown is based on the total investments.

Semiannual Report

June 30, 2021

Emerging Markets Debt Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Foreign Government Bonds—61.6%
Angola—2.0%
Angolan Government International Bond, 9.500%, due 11/12/25	$	250	$	274
Angolan Government International Bond, 9.375%, due 5/8/48		200		209
				483
Argentina—0.8%
Argentine Republic Government International Bond, 0.125%, due 7/9/41, VRN(a)		300		107
Argentine Republic Government International Bond, 0.125%, due 7/9/46, VRN(a)		125		40
Argentine Republic Government International Bond, 0.125%, due 7/9/41, VRN(a)	EUR	125		46
				193
Armenia—0.8%
Republic of Armenia International Bond, 3.600%, due 2/2/31	$	200		189
Bahrain—2.0%
Bahrain Government International Bond, 5.450%, due 9/16/32		200		199
Bahrain Government International Bond, 6.250%, due 1/25/51		300		285
				484
Belarus—0.7%
Republic of Belarus International Bond, 6.378%, due 2/24/31		200		173
Belize—0.4%
Belize Government International Bond, 4.938%, due 2/20/34, VRN(a)		213		85
Benin—0.5%
Benin Government International Bond, 6.875%, due 1/19/52	EUR	100		124
Brazil—1.7%
Brazilian Government International Bond, 5.625%, due 1/7/41	$	200		217
Fed Republic of Brazil, 3.750%, due 9/12/31		200		198
				415
Cameroon—2.0%
Republic of Cameroon International Bond, 9.500%, due 11/19/25		200		234
Republic of Cameroon—144A, 5.950%, due 7/7/32	EUR	200		237
				471
Chile—0.8%
Chile Government International Bond, 3.100%, due 1/22/61	$	200		191
Colombia—2.2%
Colombia Government International Bond, 6.125%, due 1/18/41		450		532


Issuer	Principal Amount		Value

Foreign Government Bonds—(continued)
Dominican Republic—1.4%
Dominican Republic International Bond, 5.875%, due 1/30/60	$	350	$	349
Ecuador—1.9%
Ecuador Government International Bond, 0.500%, due 7/31/30, VRN(a)		160		137
Ecuador Government International Bond, 0.500%, due 7/31/35, VRN(a)		150		103
Ecuador Government International Bond, 0.500%, due 7/31/40, VRN(a)		150		93
Ecuador Government International Bond, 0.000%, due 7/31/30		250		138
				471
Egypt—3.2%
Egypt Government International Bond, 5.875%, due 2/16/31		200		193
Egypt Government International Bond, 3.875%, due 2/16/26		250		246
Egypt Government International Bond, 7.500%, due 2/16/61		350		326
				765
El Salvador—0.8%
El Salvador Government International Bond, 8.250%, due 4/10/32		200		189
Gabon—1.3%
Gabon Government International Bond, 6.625%, due 2/6/31		300		301
Ghana—1.7%
Ghana Government International Bond, 8.875%, due 5/7/42		200		202
Ghana Government International Bond, 8.625%, due 4/7/34		200		206
				408
Indonesia—1.6%
Indonesia Government International Bond, 3.400%, due 9/18/29		350		379
Iraq—1.1%
Iraq International Bond, 6.752%, due 3/9/23		250		255
Ivory Coast—0.5%
Ivory Coast Government International Bond, 6.625%, due 3/22/48	EUR	100		125
Jamaica—1.0%
Jamaica Government International Bond, 6.750%, due 4/28/28	$	200		234
Kenya—0.8%
Kenya Government International Bond-144A, 6.300%, due 1/23/34		200		200
Lebanon—0.6%
Lebanon Government International Bond, 6.850%, due 3/23/27(b)		600		74

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Emerging Markets Debt Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Foreign Government Bonds—(continued)
Lebanon (continued)
Lebanon Government International Bond, 5.800%, due 4/14/20(b)		600	$	74
				148
Macedonia—0.5%
North Macedonia Government International Bond, 3.675%, due 6/3/26	EUR	100		131
Mexico—0.8%
Mexico Government International Bond, 3.750%, due 4/19/71	$	200		183
Nigeria—0.9%
Nigeria Government International Bond, 7.696%, due 2/23/38		200		205
Oman—1.9%
Oman Government International Bond, 6.000%, due 8/1/29		200		212
Oman Government International Bond, 6.750%, due 1/17/48		250		249
				461
Pakistan—1.0%
Pakistan Government International Bond, 6.000%, due 4/8/26		250		252
Panama—1.9%
Panama Government International Bond, 4.500%, due 5/15/47		200		227
Panama Government International Bond, 4.500%, due 4/1/56		200		227
				454
Paraguay—1.0%
Paraguay Government International Bond, 5.600%, due 3/13/48		200		235
Peru—0.7%
Peruvian Government International Bond, 3.230%, due 7/28/21		180		158
Philippines—1.1%
Philippine Government International Bond, 3.700%, due 2/2/42		250		269
Qatar—2.9%
Qatar Government International Bond, 3.750%, due 4/16/30		300		340
Qatar Government International Bond, 4.400%, due 4/16/50		300		365
				705
Romania—1.8%
Romanian Government International Bond, 4.625%, due 4/3/49	EUR	200		301
Romanian Government International Bond, 3.500%, due 4/3/34		100		135
				436


Issuer	Principal Amount		Value

Foreign Government Bonds—(continued)
Russia—2.1%
Russian Foreign Bond, 5.100%, due 3/28/35	$	200	$	238
Russian Foreign Bond, 5.625%, due 4/4/42		200		256
				494
Saudi Arabia—2.1%
Saudi Government International Bond, 2.250%, due 2/2/33		200		195
Saudi Government International Bond, 3.450%, due 2/2/61		300		299
				494
Senegal—0.5%
Senegal Government International Bond—144A, 5.375%, due 6/8/37	EUR	100		117
Serbia—1.6%
Serbia International Bond, 3.125%, due 5/15/27		300		395
South Africa—0.8%
Republic of South Africa Government International Bond, 5.650%, due 9/27/47	$	200		204
Sri Lanka—1.6%
Sri Lanka Government International Bond, 6.850%, due 3/14/24		200		138
Sri Lanka Government International Bond, 7.850%, due 3/14/29		400		253
				391
Tunisia—0.7%
Banque Centrale de Tunisie International Bond, 5.625%, due 2/17/24	EUR	150		166
Turkey—3.1%
Hazine Mustesarligi Varlik Kiralama A.S.—144A, 5.125%, due 6/22/26	$	200		200
Turkey Government International Bond, 4.875%, due 4/16/43		200		159
Turkey Government International Bond, 5.750%, due 5/11/47		200		170
Turkey Government International Bond, 5.600%, due 11/14/24		200		205
				734
Ukraine—2.9%
Ukraine Government International Bond, 1.258%, due 5/31/40, VRN(a)		200		237
Ukraine Government International Bond, 7.750%, due 9/1/22		150		157
Ukraine Government International Bond, 7.253%, due 3/15/33		300		312
				706
Uruguay—0.8%
Uruguay Government International Bond, 4.975%, due 4/20/55		150		193

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Debt Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Foreign Government Bonds—(continued)
Zambia—1.1%
Zambia Government International Bond, 8.500%, due 4/14/24	$	200	$	128
Zambia Government International Bond, 8.970%, due 7/30/27		200		126
				254
Total Foreign Government Bonds—61.6% (cost $14,892)				14,801

Foreign Corporate Bonds—32.1%
Brazil—1.7%
Atento Luxco 1 S.A., 8.000%, due 2/10/26		100		109
CSN Islands XII Corporation, 7.000%, (c)		100		100
MV24 Capital BV, 6.748%, due 6/1/34		187		207
				416
Chile—1.8%
Empresa Nacional del Petroleo, 5.250%, due 11/6/29		200		223
Kenbourne Invest S.A., 4.700%, due 1/22/28		200		201
				424
China—1.9%
CNAC HK Finbridge Co., Ltd., 4.875%, due 3/14/25		200		219
Sinopec Group Overseas Development 2015, Ltd., 4.100%, due 4/28/45		200		226
				445
Colombia—0.8%
SierraCol Energy Andina LLC—144A, 6.000%, due 6/15/28		200		203
Costa Rica—0.7%
Instituto Costarricense, 6.375%, due 5/15/43		200		172
Dominican Republic—0.9%
AES Andres BV—144A, 5.700%, due 5/4/28		200		206
Ghana—0.7%
Tullow Oil plc, 7.000%, due 3/1/25		200		177
Guatemala—0.9%
Investment Energy Resources Ltd.—144A, 6.250%, due 4/26/29		200		216
India—1.6%
Continuum Energy Levante, 4.500%, due 2/9/27		200		205
Export-Import Bank of India, 2.250%, due 1/13/31		200		186
				391


Issuer	Principal Amount		Value

Foreign Corporate Bonds—(continued)

Indonesia—3.8%
Perusahaan Perseroan Persero PT Perusahaan Listrik Negara, 5.250%, due 10/24/42	$	250	$	282
Perusahaan Perseroan Persero PT Perusahaan Listrik Negara, 5.375%, due 1/25/29		200		233
PT Bank Tabungan Negara Persero Tbk, 4.200%, due 1/23/25		200		204
PT Pertamina Persero, 2.300%, due 2/9/31		200		192
				911
Jamaica—0.9%
Sagicor Financial Co. Ltd.—144A, 5.300%, due 5/13/28		200		207
Kazakhstan—1.0%
KazMunayGas National Co. JSC, 5.750%, due 4/19/47		200		249
Malaysia—3.1%
1MDB Global Investments, Ltd., 4.400%, due 3/9/23		500		504
Petronas Capital, Ltd., 4.550%, due 4/21/50		200		247
				751
Mexico—3.3%
Banco Mercantil De Norte, 7.625%, due 12/31/99		200		226
Petroleos Mexicanos, 6.500%, due 1/23/29		200		207
Petroleos Mexicanos, 7.690%, due 1/23/50		200		191
Petroleos Mexicanos, 6.950%, due 1/28/60		200		177
				801
Mongolia—0.9%
Development Bank of Mongolia, 7.250%, due 10/23/23		200		215
Qatar—2.1%
Qatar Petroleum—144A, 3.300%, due 7/12/51		200		200
Qatar Petroleum—144A, 2.250%, due 7/12/31		300		297
				497
South Africa—0.9%
Eskom Holdings SOC, Ltd., 8.450%, due 8/10/28		200		226
Supranational—0.8%
The African Export-Import Bank—144A, 3.798%, due 5/17/31		200		204
Thailand—0.9%
Bangkik Bank PCL/HKJ, 5.000%, due 12/31/99, VRN(a)		200		211

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

Emerging Markets Debt Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands) (unaudited)


Issuer	Principal Amount		Value

Foreign Corporate Bonds—(continued)
Ukraine—0.9%
NAK Naftogaz Ukraine via Kondor Finance plc, 7.625%, due 11/8/26	$	200	$	206
United Arab Emirates—1.6%
Abu Dhabi Government International Bond, 2.700%, due 9/2/70		200		182
Finance Department Government of Sharjah, 4.375%, due 3/10/51		200		193
				375
Uzbekistan—0.9%
Ipoteka—Bank ATIB, 5.500%, due 11/19/25		200		210
Total Foreign Corporate Bonds—32.1% (cost $7,666)				7,713

Foreign Municipal Bonds—1.8%
Argentina—1.8%
Provincia de Buenos Aires, 9.950%, due 6/9/21(b)		250		114
Provincia de Buenos Aires, 9.125%, due 3/16/24		250		108
Provincia de Cordoba, 5.000%, due 6/1/27, VRN(a)		150		103
Provincia de Entre Rios Argentina, 5.000%, due 8/8/28, VRN(a)		150		96
				421
Total Foreign Municipal Bonds—1.8% (cost $426)				421

Repurchase Agreement—6.0%
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $1,443, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $1,472	$	1,443	$	1,443
Total Repurchase Agreement—6.0% (cost $1,443)				1,443
Total Investments in Securities—101.5% (cost $24,427)				24,378
Total Investments—101.5% (cost $24,427)				24,378
Liabilities, plus cash and other assets—(1.5)%				(353	)
Net assets—100.0%			$	24,025

(a) Variable/Floating interest rate security. Certain variable/floating interest rate securities are not based on a published reference rate and spread but are determined by the issuer or agent and are based on current market conditions. These securities do not indicate a reference rate and spread in their description above. Rate presented is as of June 30, 2021.

(b) Defaulted security.

VRN = Variable Rate Note

At June 30, 2021, the Fund’s Portfolio of Investments includes the following categories (as a percentage of long-term investments):

Foreign Government Bonds	64.5	%
Foreign Corporate Bonds	33.6	%
Foreign Municipal Bonds	1.9	%
Total	100.0	%

At June 30, 2021, the Fund’s Portfolio of Investments includes exposure to the following countries (as a percentage of long-term investments):

Angola	2.1	%
Argentina	2.7	%
Armenia	0.8	%
Bahrain	2.1	%
Belarus	0.8	%
Belize	0.4	%
Benin	0.5	%
Brazil	3.6	%
Cameroon	2.1	%
Chile	2.7	%
China	1.9	%
Colombia	3.2	%
Costa Rica	0.7	%
Dominican Republic	2.4	%
Ecuador	2.1	%
Egypt	3.3	%
El Salvador	0.8	%
Gabon	1.3	%
Ghana	2.6	%
Guatemala	0.9	%
India	1.7	%
Indonesia	5.6	%
Iraq	1.1	%
Ivory Coast	0.5	%
Jamaica	1.9	%
Kazakhstan	1.1	%
Kenya	0.9	%
Lebanon	0.6	%
Macedonia	0.6	%
Malaysia	3.3	%
Mexico	4.3	%
Mongolia	0.9	%
Nigeria	0.9	%
Oman	2.0	%
Pakistan	1.1	%
Panama	2.0	%
Paraguay	1.0	%
Peru	0.7	%
Philippines	1.2	%
Qatar	5.2	%
Romania	1.9	%
Russia	2.2	%
Saudi Arabia	2.2	%
Senegal	0.5	%
Serbia	1.7	%
South Africa	1.9	%
Sri Lanka	1.7	%
Supranational	0.9	%
Thailand	0.9	%
Tunisia	0.7	%
Turkey	3.2	%
Ukraine	4.0	%
United Arab Emirates	1.6	%
Uruguay	0.9	%
Uzbekistan	1.0	%
Zambia	1.1	%
Total	100.0	%

See accompanying Notes to Financial Statements.

Semiannual Report

June 30, 2021

Emerging Markets Debt Fund

Portfolio of Investments, June 30, 2021 (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)

Sold 9/15/21

Euro

Citibank N.A. London

1,273

1,552

1,512

$40

Centrally Cleared Interest Rate Swaps

Floating Rate Reference	Pay/Receive Floating Rate	Fixed Rate			Payment Frequency	Maturity Date	Cleared Exchange	Notional Amount (in thousands)		Upfront Payment Paid (Received)			Value			Unrealized Appreciation (Depreciation)
3 Month USD LIBOR	Receive		1.774	%	6M	February 2071	LCH		$260	$	3			$(17	)		$(20	)
3 Month USD LIBOR	Receive		0.750	%	6M	June 2031	LCH		263		20			17			(3	)
3 Month USD LIBOR	Receive		0.750	%	6M	June 2036	LCH		390		57			47			(10	)
3 Month USD LIBOR	Receive		1.250	%	6M	June 2051	LCH		406		69			49			(20	)
6 Month EURIBOR	Receive		(0.250	)%	1Y	June 2026	LCH		EUR 585		—			(1	)		(1	)
6 Month EURIBOR	Receive		0.000	%	1Y	June 2036	LCH		EUR 270		20			17			(3	)
6 Month EURIBOR	Receive		0.250	%	1Y	June 2041	LCH		EUR 220		14			10			(4	)
3 Month USD LIBOR	Pay		0.500	%	6M	June 2026	LCH		$485		(9	)		(10	)		(1	)
3 Month USD LIBOR	Pay		0.500	%	6M	June 2028	LCH		538		(27	)		(25	)		2
3 Month USD LIBOR	Pay		1.000	%	6M	June 2041	LCH		1,173		(187	)		(146	)		41
																	$(19	)

Centrally Cleared Credit Default Swaps

Reference Entity	Buy/Sell Protection	Fixed Rate			Payment Frequency	Maturity Date	Cleared Exchange	Notional Amount (in thousands)		Upfront Payment Paid (Received)		Value			Unrealized Appreciation (Depreciation)
Russian Federation	Buy		1.000	%	3M	June 2026	ICE	$	200		$—		$(2	)		$(2	)
Republic of South Africa	Buy		1.000	%	3M	June 2026	ICE		250		11		10			(1	)
																$(3	)
Total net unrealized appreciation (depreciation) on swaps																$(22	)

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

	Macro Allocation Fund

	The Macro Allocation Fund seeks to maximize long-term risk-adjusted total return.

	AN OVERVIEW FROM THE PORTFOLIO MANAGERS
Thomas Clarke Brian D. Singer, CFA
Thomas Clarke Brian D. Singer, CFA	The William Blair Macro Allocation Fund (Class N shares) posted a 3.84% increase, net of fees, for the six months ended June 30, 2021. By comparison, the Fund’s benchmark index, the ICE BofAML US 3-Month Treasury Bill Index (the “Index”), increased 0.02%. The first six months of 2021 stand in stark contrast to the first half of 2020. Equity markets rose, generally, with the MSCI All Country World Index (hedged) gaining 13%, while bonds generally fell, with the Bloomberg Barclays Global Aggregate losing 1.5%. This “risk-on” environment comes on the back of a continued recovery from the COVID-19 pandemic that shook markets in the first half 2020. Developed equities outperformed broad emerging equities consistent with vaccination progress, government stimulus, and economic recovery. From an equity sector perspective, cyclicals such as Energy and Financials outperformed, while defensives such as Consumer Staples and Utilities underperformed. Risk-on carried into the currency landscape as well, with the strongest performers in Brazil real, South Africa rand, and Russia ruble, and the weakest currency being the Japanese yen. The Fund’s market and currency segments were both positive during the period. Within markets, the Fund benefitted from long exposures (which may be obtained indirectly through derivatives or directly through exchange-traded funds or other securities) to U.S., United Kingdom (U.K.), Australia, Vietnam, and global energy sector equities. Detracting from the market segment performance were long exposures to Indonesia and Chile equities, and short exposure to Switzerland equities, as well as long exposure to U.S. Treasuries. Currency contributions came from long exposure to the Brazilian real, and short exposures in the Swiss franc and Thai baht. Detractors within currency were long exposures in the Turkish lira, Colombian peso, and Japanese yen. As we entered 2021, our view was that several of the macro headwinds that had been an influence on global markets had abated. There was greater optimism that the economically disruptive impact of the COVID-19 pandemic, while ongoing, would be overcome with the rollout of vaccinations in several regions. Notably, developed markets have had (for the most part) successful vaccination campaigns thus far. Vaccination campaigns have started in many developing nations, but progress to date has been limited. Nonetheless, some of the uncertainty over how long global economic activity would be constrained by the COVID-19 pandemic has mostly cleared. Another macro headwind that has abated is the specter of protectionism harming trade and growth, for which we had accounted in a macro theme. The risk arose primarily from former U.S. President Trump’s Administration, and for the last few years had been directed at China. Although U.S. President Biden’s Administration in the near term is not likely to unwind any of the trade barriers with China erected by former U.S. President Trump, increased protectionism is also not likely. Following the two-year agreement that the Trump Administration reached with China one year ago, where China pledged to increase imports from the United States, fulfilment of China’s targets has been partial to date, but China’s imports have been influenced (downward) by the COVID-19 pandemic, which was not foreseen at the time the agreement was reached. Third, the disorderly prospect of a “no-deal Brexit” in Europe was averted just before the 2020 year-end deadline. According to data released in 2021, however, there has been a sharp fall in U.K. exports to the European Union (EU), and a smaller fall in imports the other way. This may reflect adjustment to new regulatory hurdles to trade activities, as well as partly being an

Semiannual Report

June 30, 2021

Macro Allocation Fund

offset to increased pre-deadline preparations. But less U.K.-EU trade is consistent with the impact of Brexit—even with the deal reached—being growth-adverse in comparison with the previous status quo.

Our portfolio strategy accounted for the fading of the aforementioned headwinds by increasing exposure to those equity markets we believe are fundamentally attractive, and similarly by stepping into the currency opportunities that presented themselves. Our overall equity exposure is at the highest level it has been at for some years (although by no means aggressively bullish, as some markets are not sufficiently attractive to justify this). Similarly, we increased aggregate active risk within our currency strategy in the second half of 2020 after being significantly more cautious earlier due to prior headwinds, the most influential of which was the COVID-19 pandemic shock. Our view remains that that the gravitation of prices to fundamental value has a somewhat clearer path ahead than has been the case for the last year and more.

A new thematic influence came into focus in early 2021 and influenced several markets and currencies, which conventional wisdom refers to as the “reflation” theme. The influence of this theme is essentially opposite that of the fears of the economic slump of the previous 12 months. In contrast to early 2020, market expectations in early 2021 quickly evolved to that of some concern about overly rapid economic growth and potentially higher-than-desired inflation—a result of the prolonged history of easy monetary conditions, the aggressive fiscal stimulus in 2020 in developed countries, and the likelihood that vaccination against COVID-19 will result in relatively quicker lifting of lingering restrictions on economic activity. All three of these influences apply to the United States, some of them more widely.

This development caused long-term government bond yields to rise quite significantly in the United States, and to a lesser extent across all developed world markets. Consistent with this, some equity sectors suffered, in particular growth-sensitive sectors. In contrast, sectors of a more cyclical nature benefited from the reflation theme. Our strategy has been to disfavor government bonds, and this included a net short position to Germany sovereign debt. Strategy also has favored cyclical equities (such as financials and energy) over growth sectors (such as information technology). The reflation theme has therefore been a somewhat beneficial tailwind to our portfolios in these areas.

In currencies, the impact of reflation expectations has been negative for currencies like the Swiss franc and the Japanese yen, which have negative interest rates and are typically used as “funding” currencies (sold against higher-yielding currencies). We used the fall in the franc to buy back (reduce) some short exposure during the second quarter. Emerging currencies were not significantly affected overall, although the currencies of countries where growth is particularly slow, and where public indebtedness has increased significantly, are more vulnerable to increased reflation expectations. In our view, the macro theme is therefore a headwind to some fundamentally attractive currencies.

Changes to strategy over the past six months have mostly been in response to relative price movements in both markets and currencies. Exposure was increased in those markets that underperformed, such as Philippines and Malaysia equities, and decreased in those that outperformed, such as Vietnam and U.S. equities. Similarly, our changes in the currency space added to fundamentally attractive currencies such as the Brazilian real and Russian ruble, while reducing exposure in strong performers such as the South African rand and Mexican peso.

As indicated above, the exposures within the Fund are a combination of instruments, including exchange-traded funds, physical baskets of securities, and derivatives. The decision on what instrument to use is a function of liquidity, cost, precision, tax treatment, and transparency. Derivatives are used both to gain desired exposures and hedge away undesired exposures. The performance of the Fund will be predominantly dictated by the macro exposures themselves (such as long Brazil equity) as opposed to the instrument used to gain the exposure (exchange-traded fund or physical basket of securities vs. derivative).

June 30, 2021

William Blair Funds

Macro Allocation Fund

Performance Highlights (Unaudited)

Average Annual Total Returns through 6/30/2021
	Year to Date			1 Year			3 Year			5 Year			Since Inception
Class N(a)		3.84	%		7.86	%		1.49	%		1.91	%		3.61	%
Class I(a)		3.96			8.22			1.74			2.18			3.88
ICE BofAML US 3-Month Treasury Bill Index(a)		0.02			0.09			1.34			1.17			0.65
Class R6(b)		4.06			8.23			1.85			2.28			1.38
ICE BofAML US 3-Month Treasury Bill Index(b)		0.02			0.09			1.34			1.17			0.79

(a)	Since inception is for the period from November 29, 2011 (Commencement of Operations) to June 30, 2021.

(b)	Since inception is for the period from October 21, 2013 (Commencement of Operations) to June 30, 2021.

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 at www.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 ICE BofAML US 3-Month 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.

Portfolio Allocation (Unaudited)

The table below provides the allocation of the Fund’s holdings as a percent of net assets as of June 30, 2021.

Category	% of net assets
Equity Exchange-Traded Funds		62.0
Fixed Income Exchange-Traded Funds		4.2
Common Stocks		4.9
Foreign Government Bonds		12.3
Preferred Stocks		0.4
Repurchase Agreement		4.3
U.S. Government		9.8
Purchased Options		0.2
Cash and other assets, less liabilities		1.9
Total		100.0	%

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Semiannual Report

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Macro Allocation Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands)(unaudited)



Issuer	Shares		Value

Exchange-Traded Funds—66.2%
Equity Exchange-Traded Funds—62.0%
Financial Select Sector SPDR Fund		59,200	$	2,172
iShares MSCI Brazil ETF		65,000		2,635
iShares MSCI Chile ETF		42,000		1,217
iShares MSCI India ETF		8,300		367
SPDR S&P 500 ETF Trust (a)		297,700		127,433
Utilities Select Sector SPDR Fund		8,200		519
Vietnam Enterprise Investments, Ltd. Class “C”		228,300		2,211
Total Equity Exchange-Traded Funds				136,554
Fixed Income Exchange-Traded Funds—4.2%
iShares iBoxx $ Investment Grade Corporate Bond ETF		51,200		6,880
SPDR Bloomberg Barclays High Yield Bond ETF		21,900		2,408
Total Fixed Income Exchange-Traded Funds				9,288
Total Exchange-Traded Funds—66.2% (cost $102,888)				145,842

Common Stocks—4.9%

Emerging Asia—2.8%
Philippines—2.8%
Aboitiz Equity Ventures, Inc. (Industrial conglomerates)		248,168		214
Ayala Corporation (Industrial conglomerates)		33,552		550
Ayala Land, Inc. (Real estate management & development)		923,619		682
Bank of the Philippine Islands (Banks)		213,075		387
BDO Unibank, Inc. (Banks)		230,665		535
Globe Telecom, Inc. (Wireless telecommunication services)		3,160		119
GT Capital Holdings, Inc. (Diversified financial services)		11,878		148
International Container Terminal Services, Inc. (Transportation infrastructure)		119,131		399
JG Summit Holdings, Inc. (Industrial conglomerates)		344,760		439
Jollibee Foods Corporation (Hotels, restaurants & leisure)		53,147		233
Manila Electric Co. (Electric utilities)		27,347		155
Metro Pacific Investments Corporation (Diversified financial services)		1,454,264		116
Metropolitan Bank & Trust Co. (Banks)		212,149		212
PLDT, Inc. (Wireless telecommunication services)		9,033		239
SM Investments Corporation (Industrial conglomerates)		28,190		577
SM Prime Holdings, Inc. (Real estate management & development)		1,186,350		887
Universal Robina Corporation (Food products)		105,596		313
				6,205

Issuer	Shares or Principal Amount		Value

Common Stocks (continued)

Emerging Latin America—2.1%
Chile—2.1%
Banco de Chile (Banks)		6,648,294	$	656
Banco de Credito e Inversiones S.A. (Banks)		7,088		299
Banco Santander Chile (Banks)		9,607,446		475
Cencosud S.A. (Food & staples retailing)		219,957		438
Cencosud Shopping S.A		71,867		118
Cia Cervecerias Unidas S.A. (Beverages)		23,118		233
Colbun S.A. (Independent power & renewable electricity producers)		1,176,202		164
Empresas CMPC S.A. (Paper & forest products)		157,830		376
Empresas COPEC S.A. (Oil, gas & consumable fuels)		56,120		552
Enel Americas S.A. (Electric utilities)		3,115,256		457
Enel Chile S.A. (Electric utilities)		4,113,165		237
Falabella S.A. (Multiline retail)		110,904		494
				4,499
Total Common Stocks—4.9% (cost $9,799)				10,704

Foreign Government Bonds—12.3%
Brazil—4.1%
Brazil Notas do Tesouro Nacional
Serie F, 10.000%, due 1/1/25	BRL 42,370			8,990
Malaysia—5.8%
Malaysia Government Bond, 3.480%, due 3/15/23	MYR 51,730			12,775
South Africa—2.4%
Republic of South Africa Government
Bond, 7.000%, due 2/28/31	ZAR 90,163			5,418
Total Foreign Government Bonds—12.3% (cost $26,360)				27,183

Preferred Stock—0.4%
Chile—0.4%
Sociedad Quimica y Minera de Chile S.A. Class “B” (Chemicals)		20,252		954
Total Preferred Stock—0.4% (cost $856)				954

Repurchase Agreement—4.3%
Fixed Income Clearing Corporation, 0.000% dated 6/30/21, due 7/1/21, repurchase price $9,466, collateralized by U.S. Treasury Bond, 1.875%, due 2/15/41, valued at $9,656		$9,466		9,466
Total Repurchase Agreement—4.3% (cost $9,466)				9,466

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

101

Macro Allocation Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands)(unaudited)


Issuer	Principal Amount		Value

U.S. Government—9.8%
U.S. Treasury Bill, 0.080%, due 10/7/21		500	$	500
U.S. Treasury Bill, 0.081%, due 11/4/21		500		500
U.S. Treasury Bill, 0.085%, due 12/2/21		500		500
U.S. Treasury Bill, 0.100%, due 12/30/21(b)		5,000		4,999
U.S. Treasury Bill, 0.086%, due 1/27/22(b)		5,500		5,499
U.S. Treasury Bill, 0.074%, due 2/24/22(b)		3,000		2,999
U.S. Treasury Bill, 0.068%, due 3/24/22(b)		2,000		1,999
U.S. Treasury Bill, 0.058%, due 4/21/22		1,500		1,499
U.S. Treasury Bill, 0.044%, due 5/19/22(b)		1,500		1,499
U.S. Treasury Bill, 0.066%, due 6/16/22		1,500		1,499
Total U.S. Government—9.8% (cost $21,490)				21,493
Total Purchased Options—0.2% (cost $441)				561
Total Investments in Securities—98.1% (cost $171,300)				216,203
Cash and other assets, less liabilities—1.9%				4,238
Net assets—100.0%			$	220,441

(a) The SPDR S&P 500 ETF Trust’s financial statements are available free of charge on the SEC’s website at https://www.sec.gov.

(b) 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 $14,015 (in thousands).

See accompanying Notes to Financial Statements.

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Semiannual Report

June 30, 2021

Macro Allocation Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands)(unaudited)

Purchased Options Contracts

Description	Counterparty	Exercise Price/ FX Rate	Expiration Date	Number of Contracts	Notional Amount		Market Value			Premiums Paid (Received) by Fund			Unrealized Appreciation/ (Depreciation)
Calls Euro Stoxx 50	Credit Suisse International	4,150	09/17/21	442	EUR	17,964		$	324		$	258		$	66
Puts NZD Put/ JPY Call	Citibank N.A.	78	09/16/21	15,843,000	NZD	15,843		$	237		$	183		$	54
Total purchased options contracts								$	561		$	441		$	120

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
7/21/21	Brazilian Real	Citibank N.A. London		71,622		14,087		$	14,370		$	283
7/21/21	Chilean Peso	Citibank N.A. London		1,078,191		1,457			1,467			10
7/21/21	Chinese Yuan Renminbi	Citibank N.A. London		12,290		1,899			1,899			—
7/21/21	Colombian Peso	Citibank N.A. London		83,443,364		23,181			22,214			(967	)
7/21/21	Czech Koruna	Citibank N.A. London		51,236		2,393			2,382			(11	)
7/21/21	Hong Kong Dollar	Citibank N.A. London		20,738		2,670			2,670			—
7/21/21	Indonesian Rupiah	Citibank N.A. London		28,682,500		1,976			1,966			(10	)
7/21/21	Israeli Shekel	Citibank N.A. London		13,334		4,096			4,091			(5	)
7/21/21	Mexican Peso	Citibank N.A. London		348,507		17,611			17,442			(169	)
7/21/21	Philippine Peso	Citibank N.A. London		287,612		6,017			5,881			(136	)
7/21/21	Russian Ruble	Citibank N.A. London		1,807,766		25,044			24,641			(403	)
7/21/21	Singapore Dollar	Citibank N.A. London		44,792		33,797			33,310			(487	)
7/21/21	South African Rand	Citibank N.A. London		6,347		445			443			(2	)
7/21/21	South Korean Won	Citibank N.A. London		1,078,542		952			954			2
7/21/21	Taiwan Dollar	Citibank N.A. London		176,706		6,416			6,336			(80	)
7/21/21	Thai Baht	Citibank N.A. London		91,954		2,898			2,869			(29	)
7/22/21	Indian Rupee	Citibank N.A. London		924,896		12,574			12,411			(163	)
7/26/21	New Turkish Lira	Citibank N.A. London		97,205		11,320			11,024			(296	)
9/15/21	Australian Dollar	Citibank N.A. London		5,049		3,812			3,787			(25	)
9/15/21	British Pound Sterling	Citibank N.A. London		4,082		5,762			5,648			(114	)
9/15/21	Canadian Dollar	Citibank N.A. London		4,444		3,592			3,585			(7	)
9/15/21	Euro	Citibank N.A. London		3,836		4,575			4,556			(19	)
9/15/21	Japanese Yen	Citibank N.A. London		2,426,124		22,176			21,852			(324	)
9/15/21	New Zealand Dollar	Citibank N.A. London		8,083		5,666			5,649			(17	)
9/15/21	Swedish Krona	Citibank N.A. London		56,571		6,863			6,615			(248	)
9/15/21	Swiss Franc	Citibank N.A. London		2,395		2,610			2,594			(16	)
											$	(3,233	)
Sold
7/21/21	Brazilian Real	Citibank N.A. London		15,941		3,186		$	3,198		$	(12	)
7/21/21	Chilean Peso	Citibank N.A. London		5,953,540		8,265			8,103			162
7/21/21	Chinese Yuan Renminbi	Citibank N.A. London		45,146		7,052			6,972			80
7/21/21	Colombian Peso	Citibank N.A. London		14,928,367		3,949			3,974			(25	)
7/21/21	Czech Koruna	Citibank N.A. London		284,741		13,653			13,238			415
7/21/21	Hong Kong Dollar	Citibank N.A. London		102,512		13,211			13,203			8
7/21/21	Indonesian Rupiah	Citibank N.A. London		167,197,577		11,721			11,460			261
7/21/21	Israeli Shekel	Citibank N.A. London		75,407		23,254			23,133			121
7/21/21	Mexican Peso	Citibank N.A. London		62,806		3,098			3,143			(45	)
7/21/21	Philippine Peso	Citibank N.A. London		64,910		1,332			1,327			5
7/21/21	Russian Ruble	Citibank N.A. London		324,156		4,454			4,419			35
7/21/21	Singapore Dollar	Citibank N.A. London		7,926		5,899			5,895			4
7/21/21	South African Rand	Citibank N.A. London		35,894		2,621			2,508			113
7/21/21	South Korean Won	Citibank N.A. London		6,429,898		5,767			5,690			77
7/21/21	Taiwan Dollar	Citibank N.A. London		32,855		1,180			1,178			2
7/21/21	Thai Baht	Citibank N.A. London		526,160		16,852			16,416			436
7/22/21	Indian Rupee	Citibank N.A. London		176,399		2,371			2,367			4

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

103

Macro Allocation Fund

Portfolio of Investments, June 30, 2021 (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)
7/26/21	New Turkish Lira	Citibank N.A. London		16,764		1,890		1,901		$	(11	)
9/15/21	Australian Dollar	Citibank N.A. London		28,624		22,175		21,473			702
9/15/21	British Pound Sterling	Citibank N.A. London		546		758		756			2
9/15/21	Canadian Dollar	Citibank N.A. London		25,364		20,958		20,461			497
9/15/21	Euro	Citibank N.A. London		21,951		26,752		26,068			684
9/15/21	Japanese Yen	Citibank N.A. London		430,269		3,895		3,876			19
9/15/21	New Zealand Dollar	Citibank N.A. London		47,428		34,071		33,145			926
9/15/21	Swedish Krona	Citibank N.A. London		10,302		1,210		1,205			5
9/15/21	Swiss Franc	Citibank N.A. London		13,691		15,313		14,826			487
										$	4,952
Total net unrealized appreciation (depreciation) on forward foreign currency contracts										$	1,719

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
38	CAC 40 Index	July 2021	Euro		2,472		2,973		2,931		$	(42	)
42	IBEX 35 Index	July 2021	Euro		3,691		4,558		4,377			(181	)
71	OMXS 30 Index	July 2021	Swedish Krona		16,089		1,877		1,880			3
12	FTSE Taiwan Index	July 2021	U.S. Dollar		732		718		732			14
249	MSCI Singapore E TS Index	July 2021	Singapore Dollar		8,851		6,554		6,582			28
111	FTSE KLCI Index	July 2021	Malaysian Ringgit		8,508		2,089		2,049			(40	)
12	KOSPI 200 Index	September 2021	South Korean Won		1,316,550		1,152		1,169			17
50	SPI 200 Index	September 2021	Australian Dollar		9,029		6,809		6,771			(38	)
6	DAX Index	September 2021	Euro		2,329		2,790		2,762			(28	)
197	FTSE 100 Index	September 2021	British Pound Sterling		13,752		19,321		19,023			(298	)
14	FTSE MIB Index	September 2021	Euro		1,750		2,121		2,075			(46	)
279	MSCI Indonesia Index September 2021	U.S. Dollar			3,896		4,229		3,896			(333	)
246	MSCI World Energy Index	September 2021	U.S. Dollar		7,127		7,402		7,127			(275	)
10	SWISS Markets Index	September 2021	Swiss Franc		1,193		1,290		1,289			(1	)
											$	(1,220	)
Short
3	Amsterdam Index	July 2021	Euro		438		520		519		$	1
27	FTSE/JSE Top 40 Index	September 2021	South African Rand		16,167		1,166		1,132			34
220	EURO STOXX 50 Index	September 2021	Euro		8,922		10,696		10,579			117
1	MSCI China Free Net Index	September 2021	U.S. Dollar		60		60		60			—
64	MSCI Emerging Markets Index	September 2021	U.S. Dollar		4,367		4,369		4,367			2
93	MSCI Mexico Index	September 2021	U.S. Dollar		2,471		2,494		2,471			23
32	NASDAQ 100 E Mini Index	September 2021	U.S. Dollar		9,311		8,905		9,311			(406	)
495	S&P 500 E Mini Index	September 2021	U.S. Dollar		106,143		104,524		106,143			(1,619	)
11	S&P E Mini Com Ser Index	September 2021	U.S. Dollar		1,165		1,146		1,165			(19	)
7	XAK Technology	September 2021	U.S. Dollar		1,041		999		1,041			(42	)
12	XAY Cons Discret	September 2021	U.S. Dollar		2,164		2,095		2,164			(69	)
28	10YR Can Bond	September 2021	Canadian Dollar		4,075		3,250		3,287			(37	)
											$	(2,015	)
Total net unrealized appreciation (depreciation) on futures contracts											$	(3,235	)

See accompanying Notes to Financial Statements.

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Macro Allocation Fund

Portfolio of Investments, June 30, 2021 (all dollar amounts in thousands)(unaudited)

Centrally Cleared Interest Rate Swaps

Floating Rate Reference	Pay/Receive Floating Rate	Fixed Rate	Payment Frequency	Maturity Dates	Cleared Exchange	Notional Amount (in thousands)	Upfront Payment Paid (Received)			Value			Unrealized Appreciation (Depreciation)
Brazil CDI ON Deposit Rate	Pay	6.010%	1M	January 2023	CME	BRL 92,768		$(109	)	$	(123	)		$	(14	)
China 1-Week Repo Rate	Pay	2.850%	3M	June 2026	LCH	CNY 39,940		1			21				20
														$	6

Total Return Swaps

Reference Entity	Pay/Receive Floating Rate	Floating Rates	Maturity Dates	Counterparty	Notional Amount (in thousands)		Market Value			Unrealized Appreciation (Depreciation)
CSI 500 Net Total Return Index	Pay	(1,305) bp	Sep 2021	Credit Suisse International		$6,324		$1,241			$	1,241
EUR-Bund Future	Receive	0 bp	Sep 2021	Credit Suisse International		EUR 859		(5	)			(5	)
MSCI Philippines Index Future	Pay	0 bp	Sep 2021	Goldman Sachs International		$527		(4	)			(4	)
RTS Index Future	Pay	0 bp	Sep 2021	Credit Suisse International		2,585		(38	)			(38	)
10YR T-Note Future	Pay	0 bp	Sep 2021	Credit Suisse International		3,038		10				10
5YR T-Note Future	Pay	0 bp	Sep 2021	Credit Suisse International		12,760		(47	)			(47	)
											$	1,157

Centrally Cleared Credit Default Swap

Reference
Entity

Buy/Sell
Protection

Fixed Rate

Payment
Frequency

Maturity
Date

Cleared
Exchange

Notional
Amount
(in thousands)

Upfront
Payment
Paid
(Received)

Value

Unrealized
Appreciation
(Depreciation)

ITRAXX-EUROPE S35V1-5Y

Sell

1.000%

June 2026

ICE

EUR 3,865

$123

—

Total net unrealized appreciation (depreciation) on swaps

1,163

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

105

Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	Growth Fund			Large Cap Growth Fund			Mid Cap Growth Fund			Small-Mid Cap Core Fund
Assets
Investments in securities, at cost		$	169,370		$	517,781		$	61,296		$	39,429
Investments in securities, at value		$	326,608		$	818,037		$	86,902		$	51,082
Receivable for securities sold			—			4,807			1,047			34
Receivable for fund shares sold			179			1,212			4			1,545
Receivable from Adviser			—			49			19			12
Dividend and interest receivable			99			141			16			22
Total assets			326,886			824,246			87,988			52,695
Liabilities
Payable for securities purchased			—			4,928			1,882			1,631
Payable for fund shares redeemed			142			576			11			—
Management fee payable			197			390			63			35
Distribution fee payable			7			33			1			—
Other payables and accrued expenses			73			113			53			70
Total liabilities			419			6,040			2,010			1,736
Net assets		$	326,467		$	818,206		$	85,978		$	50,959
Capital
Composition of net assets
Paid in capital		$	138,485		$	481,754		$	53,322		$	50,767
Total distributable earnings (loss)			187,982			336,452			32,656			192
Net assets		$	326,467		$	818,206		$	85,978		$	50,959

Class N shares
Net assets		$	34,360		$	164,108		$	5,621			—
Shares outstanding			2,725,049			7,175,466			421,127			—
Net asset value per share		$	12.61		$	22.87		$	13.35			—
Class I shares
Net assets		$	278,636		$	455,229		$	79,711		$	30,517
Shares outstanding			18,036,289			18,699,598			5,442,892			2,002,130
Net asset value per share		$	15.45		$	24.34		$	14.64		$	15.24
Class R6 shares
Net assets		$	13,471		$	198,869		$	646		$	20,442
Shares outstanding			869,811			8,175,683			44,075			1,340,474
Net asset value per share		$	15.49		$	24.32		$	14.66		$	15.25

See accompanying Notes to Financial Statements.

106

Semiannual Report

June 30, 2021

Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	Growth Fund				Large Cap Growth Fund				Mid Cap Growth Fund				Small-Mid Cap Core Fund
Investment income
Dividends		$	895			$	2,473			$	160			$	155
Total income			895				2,473				160				155
Expenses
Investment advisory fees			1,148				2,201				377				178
Distribution fees			43				184				7				—
Custodian fees			32				28				30				44
Transfer agent fees			36				57				7				1
Sub-transfer agent fees
Class N			22				96				3				—
Class I			69				188				47				15
Professional fees			19				42				14				16
Registration fees			26				49				28				17
Shareholder reporting fees			8				36				1				1
Trustee fees			10				21				3				3
Other expenses			9				18				5				4
Total expenses before expense limitation			1,422				2,920				522				279
Expenses waived or reimbursed by the Adviser
Class N			(3	)			(110	)			(8	)			—
Class I			—				(226	)			(109	)			(68	)
Class R6			—				(60	)			(1	)			(26	)
Total expenses waived or reimbursed by the Adviser			(3	)			(396	)			(118	)			(94	)
Net expenses			1,419				2,524				404				185
Net investment income (loss)			(524	)			(51	)			(244	)			(30	)
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities			22,076				33,132				5,861				2,113
Total net realized gain (loss)			22,076				33,132				5,861				2,113
Change in net unrealized appreciation (depreciation) of:
Investments in securities			16,781				68,610				(2,575	)			4,020
Change in net unrealized appreciation (depreciation)			16,781				68,610				(2,575	)			4,020
Net increase (decrease) in net assets resulting from operations		$	38,333			$	101,691			$	3,042			$	6,103

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

107

Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	Growth Fund						Large Cap Growth Fund						Mid Cap Growth Fund						Small-Mid Cap Core Fund
	2021			2020			2021			2020			2021			2020			2021			2020
Operations
Net investment income (loss)	$	(524	)	$	(660	)	$	(51	)	$	1,218		$	(244	)	$	(342	)	$	(30	)	$	6
Net realized gain (loss) on investments, and other assets and liabilities		22,076			42,176			33,132			34,530			5,861			6,414			2,113			(13,678	)
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		16,781			40,608			68,610			144,802			(2,575	)		12,060			4,020			7,247
Net increase (decrease) in net assets resulting from operations		38,333			82,124			101,691			180,550			3,042			18,132			6,103			(6,425	)
Distributions to shareholders from
Class N		—			(4,769	)		—			(5,187	)		—			(466	)		—			—
Class I		—			(27,747	)		—			(14,681	)		—			(5,249	)		—			—
Class R6		—			(1,332	)		—			(6,012	)		—			(42	)		—			—
Total distributions		—			(33,848	)		—			(25,880	)		—			(5,757	)		—			—
Capital stock transactions
Proceeds from sale of shares		11,141			28,188			149,862			494,318			4,588			11,489			17,123			266,207
Shares issued in reinvestment of income dividends and capital gain distributions		—			32,736			—			22,621			—			5,537			—			—
Less cost of shares redeemed		(20,258	)		(65,536	)		(146,216	)		(262,574	)		(5,622	)		(18,977	)		(2,312	)		(236,325	)
Net increase (decrease) in net assets resulting from capital share transactions		(9,117	)		(4,612	)		3,646			254,365			(1,034	)		(1,951	)		14,811			29,882
Increase (decrease) in net assets		29,216			43,664			105,337			409,035			2,008			10,424			20,914			23,457
Net assets
Beginning of period		297,251			253,587			712,869			303,834			83,970			73,546			30,045			6,588
End of period	$	326,467		$	297,251		$	818,206		$	712,869		$	85,978		$	83,970		$	50,959		$	30,045

See accompanying Notes to Financial Statements.

108

Semiannual Report

June 30, 2021

Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	Small-Mid Cap Growth Fund		Small Cap Growth Fund		Small Cap Value Fund
Assets
Investments in securities, at cost	$	2,362,544	$	513,988	$	31,793
Investments in securities, at value	$	3,442,842	$	739,925	$	48,460
Receivable for securities sold		42,650		287		—
Receivable for fund shares sold		2,492		7,303		28
Receivable from Adviser		157		8		21
Dividend and interest receivable		411		82		24
Total assets		3,488,552		747,605		48,533
Liabilities
Payable for securities purchased		1,773		2,791		—
Payable for fund shares redeemed		5,066		171		35
Management fee payable		2,850		664		32
Distribution fee payable		55		39		2
Other payables and accrued expenses		549		141		85
Total liabilities		10,293		3,806		154
Net assets	$	3,478,259	$	743,799	$	48,379
Capital
Composition of net assets
Paid in capital	$	1,930,698	$	433,121	$	38,207
Total distributable earnings (loss)		1,547,561		310,678		10,172
Net assets	$	3,478,259	$	743,799	$	48,379

Class N shares
Net assets	$	267,143	$	191,361	$	10,865
Shares outstanding		7,503,036		4,916,421		708,190
Net asset value per share	$	35.60	$	38.92	$	15.34
Class I shares
Net assets	$	2,881,276	$	428,670	$	25,982
Shares outstanding		75,817,606		9,637,811		1,625,002
Net asset value per share	$	38.00	$	44.48	$	15.99
Class R6 shares
Net assets	$	329,840	$	123,768	$	11,532
Shares outstanding		8,665,512		2,778,624		721,866
Net asset value per share	$	38.06	$	44.54	$	15.98

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

109

Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	Small-Mid Cap Growth Fund			Small Cap Growth Fund			Small Cap Value Fund
Investment income
Dividends	$	5,852		$	1,068		$	390
Less foreign tax withheld		(69	)		(13	)		—
Total income		5,783			1,055			390
Expenses
Investment advisory fees		17,767			3,939			211
Distribution fees		379			235			11
Custodian fees		41			36			38
Transfer agent fees		116			45			9
Sub-transfer agent fees
Class N		217			131			6
Class I		1,831			193			59
Professional fees		103			33			14
Registration fees		44			32			41
Shareholder reporting fees		95			26			2
Trustee fees		120			24			3
Other expenses		65			18			4
Total expenses before expense limitation		20,778			4,712			398
Expenses waived or reimbursed by the Adviser
Class N		(116	)		(46	)		(20	)
Class I		(830	)		(8	)		(110	)
Class R6		—			—			(20	)
Total expenses waived or reimbursed by the Adviser		(946	)		(54	)		(150	)
Net expenses		19,832			4,658			248
Net investment income (loss)		(14,049	)		(3,603	)		142
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities		318,292			77,885			7,739
Redemptions in-kind		89,621			—			—
Total net realized gain (loss)		407,913			77,885			7,739
Change in net unrealized appreciation (depreciation) of:
Investments in securities		(115,298	)		11,979			816
Change in net unrealized appreciation (depreciation)		(115,298	)		11,979			816
Net increase (decrease) in net assets resulting from operations	$	278,566		$	86,261		$	8,697

See accompanying Notes to Financial Statements.

110

Semiannual Report

June 30, 2021

Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	Small-Mid Cap Growth Fund						Small Cap Growth Fund						Small Cap Value Fund
	2021			2020			2021			2020			2021			2020
Operations
Net investment income (loss)	$	(14,049	)	$	(20,276	)	$	(3,603	)	$	(4,664	)	$	142		$	838
Net realized gain (loss) on investments, and other assets and liabilities		407,913			172,271			77,885			88,364			7,739			(4,844	)
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		(115,298	)		703,070			11,979			88,533			816			(26,660	)
Net increase (decrease) in net assets resulting from operations		278,566			855,065			86,261			172,233			8,697			(30,666	)
Distributions to shareholders from
Class N		—			(5,612	)		—			(18,482	)		—			(2,130	)
Class I		—			(51,667	)		—			(35,006	)		—			(26,640	)
Class R6		—			(1,737	)		—			(9,448	)		—			(202	)
Total distributions		—			(59,016	)		—			(62,936	)		—			(28,972	)
Capital stock transactions
Proceeds from sale of shares		545,344			829,348			76,296			113,709			6,361			22,998
Shares issued in reinvestment of income dividends and capital gain distributions		—			58,002			—			62,018			—			27,878
Less cost of shares redeemed		(922,733	)		(1,012,131	)		(93,366	)		(280,953	)		(26,580	)		(106,615	)
Net increase (decrease) in net assets resulting from capital share transactions		(377,389	)		(124,781	)		(17,070	)		(105,226	)		(20,219	)		(55,739	)
Increase (decrease) in net assets		(98,823	)		671,268			69,191			4,071			(11,522	)		(115,377	)
Net assets
Beginning of period		3,577,082			2,905,814			674,608			670,537			59,901			175,278
End of period	$	3,478,259		$	3,577,082		$	743,799		$	674,608		$	48,379		$	59,901

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

111

Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	Global Leaders Fund		International Leaders Fund			International Growth Fund		Institutional International Growth Fund
Assets
Investments in securities, at cost	$	73,362		$	824,523	$	1,354,152	$	754,139
Investments in securities, at value	$	138,343		$	1,196,444	$	2,343,158	$	1,312,319
Cash		3			99		142		80
Foreign currency, at value (cost $12; $254; $1,535; $266)		12			254		1,527		265
Receivable for securities sold		322			8,610		10,988		6,219
Receivable for fund shares sold		180			1,380		343		452
Receivable from Adviser		18			72		1		—
Dividend and interest receivable		128			1,526		5,073		2,975
Total assets		139,006			1,208,385		2,361,232		1,322,310
Liabilities
Payable for securities purchased		—			10,046		3,024		1,692
Payable for fund shares redeemed		1			150		2,420		49
Management fee payable		95			853		1,958		1,037
Distribution fee payable		3			7		62		—
Foreign capital gains tax liability		—			955		717		447
Other payables and accrued expenses		79			121		521		278
Total liabilities		178			12,132		8,702		3,503
Net assets	$	138,828		$	1,196,253	$	2,352,530	$	1,318,807
Capital
Composition of net assets
Paid in capital	$	68,209		$	780,173	$	1,098,916	$	588,777
Total distributable earnings (loss)		70,619			416,080		1,253,614		730,030
Net assets	$	138,828		$	1,196,253	$	2,352,530	$	1,318,807

Class N shares
Net assets	$	12,925		$	35,254	$	300,351		—
Shares outstanding		670,023			1,462,509		7,158,228		—
Net asset value per share	$	19.29		$	24.10	$	41.96		—
Class I shares
Net assets	$	121,059		$	511,382	$	1,888,879		—
Shares outstanding		6,248,056			21,092,697		43,928,268		—
Net asset value per share	$	19.38		$	24.24	$	43.00		—
Institutional/Class R6 shares
Net assets	$	4,844		$	649,617	$	163,300	$	1,318,807
Shares outstanding		249,897			26,786,079		3,796,142		59,679,373
Net asset value per share	$	19.39		$	24.25	$	43.02	$	22.10

See accompanying Notes to Financial Statements.

112

Semiannual Report

June 30, 2021

Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	Global Leaders Fund				International Leaders Fund				International Growth Fund				Institutional International Growth Fund
Investment income
Dividends		$	515			$	6,221			$	12,773			$	7,218
Less foreign tax withheld			(38	)			(747	)			(1,297	)			(750	)
Interest			—				—				1,255				7
Total income			477				5,474				12,731				6,475
Expenses
Investment advisory fees			542				4,946				11,628				6,243
Distribution fees			15				35				363				—
Custodian fees			41				87				152				162
Transfer agent fees			4				26				60				21
Sub-transfer agent fees
Class N			8				17				219				—
Class I			41				170				773				—
Professional fees			26				66				114				92
Registration fees			23				43				29				12
Shareholder reporting fees			2				11				40				5
Trustee fees			5				34				78				53
Other expenses			5				24				39				18
Total expenses before expense limitation			712				5,459				13,495				6,606
Expenses waived or reimbursed by the Adviser
Class N			(15	)			(17	)			(14	)			—
Class I			(106	)			(170	)			—				—
Institutional/Class R6			(3	)			(171	)			—				—
Total expenses waived or reimbursed by the Adviser			(124	)			(358	)			(14	)			—
Net expenses			588				5,101				13,481				6,606
Net investment income (loss)			(111	)			373				(750	)			(131	)
Realized and unrealized gain (loss)
Net realized gain (loss) on transactions from:
Investments in securities (net of foreign capital gains tax paid $—; $67; $—; $13)			5,074				47,585				236,570				151,598
Foreign currency transactions			2				(77	)			(225	)			(159	)
Total net realized gain (loss)			5,076				47,508				236,345				151,439
Change in net unrealized appreciation (depreciation) of:
Investments in securities (net of foreign capital gains tax accrual $—; $7; $274; $21)			8,538				25,683				(47,769	)			(44,644	)
Foreign currency translations			(6	)			(23	)			(160	)			(79	)
Change in net unrealized appreciation (depreciation)			8,532				25,660				(47,929	)			(44,723	)
Net increase (decrease) in net assets resulting from operations		$	13,497			$	73,541			$	187,666			$	106,585

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

113

Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	Global Leaders Fund						International Leaders Fund						International Growth Fund						Institutional International Growth Fund
	2021			2020			2021			2020			2021			2020			2021			2020
Operations
Net investment income (loss)	$	(111	)	$	(101	)	$	373		$	449		$	(750	)	$	(5,712	)	$	(131	)	$	(553	)
Net realized gain (loss) on investments, and other assets and liabilities		5,076			24,259			47,508			8,912			236,345			74,910			151,439			258,776
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		8,532			7,605			25,660			191,243			(47,929	)		491,289			(44,723	)		130,546
Net increase (decrease) in net assets resulting from operations		13,497			31,763			73,541			200,604			187,666			560,487			106,585			388,769
Distributions to shareholders from
Class N		—			(1,323	)		—			(140	)		—			(2,350	)		—			—
Class I		—			(12,213	)		—			(2,856	)		—			(21,253	)		—			—
Institutional/Class R6		—			(323	)		—			(5,774	)		—			(1,273	)		—			(151,353	)
Total distributions		—			(13,859	)		—			(8,770	)		—			(24,876	)		—			(151,353	)
Capital stock transactions
Proceeds from sale of shares		7,553			17,101			231,568			390,602			98,730			345,376			29,938			148,064
Shares issued in reinvestment of income dividends and capital gain distributions		—			13,852			—			8,654			—			23,253			—			150,369
Less cost of shares redeemed		(4,404	)		(98,384	)		(209,209	)		(144,641	)		(246,516	)		(700,649	)		(144,198	)		(1,102,278	)
Net increase (decrease) in net assets resulting from capital share transactions		3,149			(67,431	)		22,359			254,615			(147,786	)		(332,020	)		(114,260	)		(803,845	)
Increase (decrease) in net assets		16,646			(49,527	)		95,900			446,449			39,880			203,591			(7,675	)		(566,429	)
Net assets
Beginning of period		122,182			171,709			1,100,353			653,904			2,312,650			2,109,059			1,326,482			1,892,911
End of period	$	138,828		$	122,182		$	1,196,253		$	1,100,353		$	2,352,530		$	2,312,650		$	1,318,807		$	1,326,482

See accompanying Notes to Financial Statements.

114

Semiannual Report

June 30, 2021

Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	International Small Cap Growth Fund			Emerging Markets Leaders Fund		Emerging Markets Growth Fund		Emerging Markets Small Cap Growth Fund
Assets
Investments in securities, at cost		$	275,367	$	263,058	$	826,669		$	388,692
Investments in securities, at value		$	357,697	$	344,060	$	1,260,555		$	497,336
Cash			—		—		—			849
Foreign currency, at value (cost $103; $8,233; $1,400; $108)			103		8,233		1,399			108
Receivable for securities sold			—		—		4,003			795
Receivable for fund shares sold			10,250		60		1,447			365
Receivable from Adviser			—		24		—			—
Dividend and interest receivable			710		366		1,743			387
Total assets			368,760		352,743		1,269,147			499,840
Liabilities
Payable for securities purchased			235		33,645		797			3,336
Payable for fund shares redeemed			147		8		3,327			49
Payable to custodian			—		—		316			—
Management fee payable			291		255		1,127			378
Distribution fee payable			1		—		7			1
Foreign capital gains tax liability			—		2,142		4,574			4,862
Other payables and accrued expenses			146		158		489			360
Total liabilities			820		36,208		10,637			8,986
Net assets		$	367,940	$	316,535	$	1,258,510		$	490,854
Capital
Composition of net assets
Paid in capital		$	235,472	$	206,602	$	672,413		$	357,475
Total distributable earnings (loss)			132,468		109,933		586,097			133,379
Net assets		$	367,940	$	316,535	$	1,258,510		$	490,854

Class N shares
Net assets		$	3,201	$	2,223	$	35,790		$	4,254
Shares outstanding			171,007		161,597		1,760,729			168,597
Net asset value per share		$	18.72	$	13.75	$	20.33		$	25.23
Class I shares
Net assets		$	147,051	$	55,679	$	195,390		$	166,794
Shares outstanding			7,750,893		4,036,654		9,474,857			6,548,723
Net asset value per share		$	18.97	$	13.79	$	20.62		$	25.47
Class R6 shares
Net assets		$	217,688	$	258,633	$	1,027,330		$	319,806
Shares outstanding			11,405,583		18,765,701		49,330,454			12,532,097
Net asset value per share		$	19.09	$	13.78	$	20.83		$	25.52

See accompanying Notes to Financial Statements.

June 30, 2021

William Blair Funds

115

Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	International Small Cap Growth Fund				Emerging Markets Leaders Fund			Emerging Markets Growth Fund			Emerging Markets Small Cap Growth Fund
*Investment income*
Dividends		$	2,061		$	1,522		$	5,838			$	1,306
Less foreign tax withheld			(253	)		(184	)		(822	)			(128	)
Interest			102			—			—				—
Total income			1,910			1,338			5,016				1,178
*Expenses*
Investment advisory fees			1,710			1,526			6,738				1,917
Distribution fees			4			3			41				5
Custodian fees			71			61			186				111
Transfer agent fees			10			8			29				15
Sub-transfer agent fees
Class N			2			1			17				2
Class I			64			23			56				54
Professional fees			49			37			73				62
Registration fees			26			30			31				26
Shareholder reporting fees			13			4			4				11
Trustee fees			11			9			37				10
Other expenses			8			8			24				8
Total expenses before expense limitation			1,968			1,710			7,236				2,221
Expenses waived or reimbursed by the Adviser
Class N			—			(2	)		—				(1	)
Class I			—			(42	)		—				(7	)
Class R6			—			(123	)		—				—
Total expenses waived or reimbursed by the Adviser			—			(167	)		—				(8	)
Net expenses			1,968			1,543			7,236				2,213
Net investment income (loss)			(58	)		(205	)		(2,220	)			(1,035	)
*Realized and unrealized gain (loss)*
Net realized gain (loss) on transactions from:
Investments in securities (net of foreign capital gains tax paid $—; $392; $1,069; $1)			44,720			26,245			136,684				32,987
Foreign currency transactions			(14	)		(22	)		(598	)			(269	)
Total net realized gain (loss)			44,706			26,223			136,086				32,718
Change in net unrealized appreciation (depreciation) of:
Investments in securities (net of foreign capital gains tax accrual $—; $674; $1,684; $4,340)			(19,738	)		(16,875	)		(13,300	)			13,737
Foreign currency translations			(43	)		43			(14	)			(6	)
Change in net unrealized appreciation (depreciation)			(19,781	)		(16,832	)		(13,314	)			13,731
Net increase (decrease) in net assets resulting from operations		$	24,867		$	9,186		$	120,552			$	45,414

See accompanying Notes to Financial Statements.

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Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	International Small Cap Growth Fund						Emerging Markets Leaders Fund						Emerging Markets Growth Fund						Emerging Markets Small Cap Growth Fund
	2021			2020			2021			2020			2021			2020			2021			2020
*Operations*
Net investment income (loss)	$	(58	)	$	(46	)	$	(205	)	$	75		$	(2,220	)	$	(2,057	)	$	(1,035	)	$	(188	)
Net realized gain (loss) on investments, and other assets and liabilities		44,706			32,819			26,223			8,003			136,086			74,647			32,718			46,512
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		(19,781	)		41,601			(16,832	)		49,105			(13,314	)		265,671			13,731			29,571
Net increase (decrease) in net assets resulting from operations		24,867			74,374			9,186			57,183			120,552			338,261			45,414			75,895
*Distributions to shareholders from*
Class N		—			(63	)		—			(15	)		—			(531	)		—			—
Class I		—			(3,008	)		—			(621	)		—			(4,443	)		—			(65	)
Class R6		—			(4,066	)		—			(2,293	)		—			(42,354	)		—			(129	)
Total distributions		—			(7,137	)		—			(2,929	)		—			(47,328	)		—			(194	)
*Capital stock transactions*
Proceeds from sale of shares		29,212			42,647			122,211			61,028			210,479			318,162			173,762			71,699
Shares issued in reinvestment of income dividends and capital gain distributions		—			6,416			—			2,899			—			44,146			—			191
Less cost of shares redeemed		(23,020	)		(88,485	)		(76,999	)		(94,327	)		(268,257	)		(247,697	)		(35,731	)		(117,803	)
Net increase (decrease) in net assets resulting from capital share transactions		6,192			(39,422	)		45,212			(30,400	)		(57,778	)		114,611			138,031			(45,913	)
Increase (decrease) in net assets		31,059			27,815			54,398			23,854			62,774			405,544			183,445			29,788
*Net assets*
Beginning of period		336,881			309,066			262,137			238,283			1,195,736			790,192			307,409			277,621
End of period	$	367,940		$	336,881		$	316,535		$	262,137		$	1,258,510		$	1,195,736		$	490,854		$	307,409

See accompanying Notes to Financial Statements.

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117

Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	Bond Fund				Income Fund			Low Duration Fund
*Assets*
Investments in securities, at cost	$	319,211		$	50,758		$	139,422
Investments in securities, at value	$	335,143		$	51,860		$	139,942
Cash		497			—			28
Receivable for securities sold		7,726			1,213			21,641
Receivable for fund shares sold		377			152			65
Receivable from Adviser		4			2			16
Dividend and interest receivable		1,871			220			343
Total assets		345,618			53,447			162,035
*Liabilities*
Security sold, not yet purchased, at value (proceeds $5,350; $1,070; $21,129)		5,326			1,065			21,080
Payable for variation margin on centrally cleared swaps		3			—			—
Payable for securities purchased		4,184			200			—
Payable for fund shares redeemed		369			62			147
Management fee payable		83			15			37
Distribution fee payable		5			2			2
Distributions payable to shareholders		124			4			23
Other payables and accrued expenses		93			50			53
Total liabilities		10,187			1,398			21,342
Net assets	$	335,431		$	52,049		$	140,693
*Capital*
Composition of net assets
Paid in capital	$	341,599		$	58,283		$	170,819
Total distributable earnings (loss)		(6,168	)		(6,234	)		(30,126	)
Net assets	$	335,431		$	52,049		$	140,693

Class N shares
Net assets	$	39,108		$	17,205		$	16,119
Shares outstanding		3,707,731			2,009,770			1,881,820
Net asset value per share	$	10.55		$	8.56		$	8.57
Class I shares
Net assets	$	246,624		$	34,654		$	102,003
Shares outstanding		23,630,357			4,075,582			11,916,949
Net asset value per share	$	10.44		$	8.50		$	8.56
Class R6 shares
Net assets	$	49,699		$	190		$	22,571
Shares outstanding		4,764,363			22,287			2,635,669
Net asset value per share	$	10.43		$	8.50		$	8.56

See accompanying Notes to Financial Statements.

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Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	Bond Fund				Income Fund			Low Duration Fund
*Investment income*
Interest	$	3,897		$	529		$	816
Total income		3,897			529			816
*Expenses*
Investment advisory fees		483			99			244
Distribution fees		29			16			12
Custodian fees		48			38			47
Transfer agent fees		47			6			9
Sub-transfer agent fees
Class N		27			15			8
Class I		84			11			22
Professional fees		33			15			35
Registration fees		33			27			30
Shareholder reporting fees		7			3			2
Trustee fees		11			3			5
Other expenses		8			5			6
Total expenses before expense limitation		810			238			420
Expenses waived or reimbursed by the Adviser
Class N		(20	)		(8	)		(13	)
Class I		(44	)		—			(58	)
Class R6		(4	)		—			(21	)
Total expenses waived or reimbursed by the Adviser		(68	)		(8	)		(92	)
Net expenses		742			230			328
Net investment income (loss)		3,155			299			488
*Realized and unrealized gain (loss)*
Net realized gain (loss) on transactions from:
Investments in securities		674			262			314
Swaps		(1,427	)		(460	)		—
Total net realized gain (loss)		(753	)		(198	)		314
Change in net unrealized appreciation (depreciation) of:
Investments in securities		(6,878	)		(907	)		(645	)
Swaps		836			316			—
Change in net unrealized appreciation (depreciation)		(6,042	)		(591	)		(645	)
Net increase (decrease) in net assets resulting from operations	$	(3,640	)	$	(490	)	$	157

See accompanying Notes to Financial Statements.

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Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	Bond Fund						Income Fund						Low Duration Fund
	2021			2020			2021			2020			2021			2020
*Operations*
Net investment income (loss)	$	3,155		$	6,928		$	299		$	829		$	488		$	1,343
Net realized gain (loss) on investments, and other assets and liabilities		(753	)		3,824			(198	)		161			314			(409	)
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities		(6,042	)		9,883			(591	)		1,281			(645	)		1,479
Net increase (decrease) in net assets resulting from operations		(3,640	)		20,635			(490	)		2,271			157			2,413
*Distributions to shareholders from*
Class N		(544	)		(1,089	)		(195	)		(546	)		(158	)		(189	)
Class I		(3,432	)		(7,496	)		(408	)		(1,009	)		(1,177	)		(1,833	)
Class R6		(723	)		(1,641	)		(1	)		(2	)		(390	)		(1,168	)
Total distributions		(4,699	)		(10,226	)		(604	)		(1,557	)		(1,725	)		(3,190	)
*Capital stock transactions*
Proceeds from sale of shares		59,350			95,911			9,305			33,540			56,197			166,102
Shares issued in reinvestment of income dividends and capital gain distributions		3,949			8,711			568			1,470			1,557			2,649
Less cost of shares redeemed		(40,249	)		(76,446	)		(25,052	)		(18,745	)		(73,873	)		(86,109	)
Net increase (decrease) in net assets resulting from capital share transactions		23,050			28,176			(15,179	)		16,265			(16,119	)		82,642
Increase (decrease) in net assets		14,711			38,585			(16,273	)		16,979			(17,687	)		81,865
*Net assets*
Beginning of period		320,720			282,135			68,322			51,343			158,380			76,515
End of period	$	335,431		$	320,720		$	52,049		$	68,322		$	140,693		$	158,380

See accompanying Notes to Financial Statements.

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Statements of Assets and Liabilities

As of June 30, 2021 (dollar amounts in thousands) (unaudited)

	Emerging Markets Debt Fund			Macro Allocation Fund
*Assets*
Investments in securities, at cost	$	24,427		$	171,300
Investments in securities, at value	$	24,378		$	216,203
Cash		400			—
Segregated cash at broker		84			—
Receivable for securities sold		354			3,802
Receivable for fund shares sold		25			164
Receivable from Adviser		17			13
Dividend and interest receivable		312			1,212
Unrealized appreciation on swap contracts		—			1,251
Unrealized appreciation on forward foreign currency contracts		40			5,340
Total assets		25,610			227,985
*Liabilities*
Payable for futures variation margin		—			130
Payable for variation margin on centrally cleared swaps		5			23
Payable for securities purchased		1,538			—
Payable for fund shares redeemed		8			130
Cash received as collateral, due to broker		—			3,170
Unrealized depreciation on swap contracts		—			94
Unrealized depreciation on forward foreign currency contracts		—			3,621
Management fee payable		13			171
Distribution fee payable		—			1
Other payables and accrued expenses		21			204
Total liabilities		1,585			7,544
Net assets	$	24,025		$	220,441
*Capital*
Composition of net assets
Paid in capital	$	24,028		$	390,320
Total distributable earnings (loss)		(3	)		(169,879	)
Net assets	$	24,025		$	220,441

Class N shares
Net assets	$	—		$	7,124
Shares outstanding		—			627,647
Net asset value per share	$	—		$	11.35
Class I shares
Net assets	$	1,151		$	95,007
Shares outstanding		115,148			8,422,191
Net asset value per share	$	10.00		$	11.28
Class R6 shares
Net assets	$	22,874		$	118,310
Shares outstanding		2,287,676			10,483,787
Net asset value per share	$	10.00		$	11.29

See accompanying Notes to Financial Statements.

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Statements of Operations

For the Period Ended June 30, 2021 (all amounts in thousands) (unaudited)

	Emerging Markets Debt Fund (a)			Macro Allocation Fund
*Investment income*
Dividends	$	—		$	1,532
Less foreign tax withheld		—			(77	)
Interest		111			866
Total income		111			2,321
*Expenses*
Investment advisory fees		15			1,158
Distribution fees		—			9
Custodian fees		4			110
Transfer agent fees		2			28
Sub-transfer agent fees
Class N		—			5
Class I		—			72
Professional fees		7			45
Registration fees		4			34
Shareholder reporting fees		1			9
Trustee fees		1			19
Other expenses		1			33
Total expenses before expense limitation		35			1,522
Expenses waived or reimbursed by the Adviser
Class N		—			(4	)
Class I		(1	)		(57	)
Class R6		(19	)		(24	)
Total expenses waived or reimbursed by the Adviser		(20	)		(85	)
Net expenses		15			1,437
Net investment income (loss)		96			884
*Realized and unrealized gain (loss)*
Net realized gain (loss) on transactions from:
Investments in securities		19			39,580
Futures contracts		—			(18,587	)
Swaps		(3	)		(265	)
Forward foreign currency contracts		4			(1,304	)
Foreign currency transactions		(1	)		—
Total net realized gain (loss)		19			19,424
Change in net unrealized appreciation (depreciation) of:
Investments in securities		(49	)		(13,137	)
Futures contracts		—			2,804
Swaps		(22	)		591
Forward foreign currency contracts		40			907
Foreign currency translations		1			17
Change in net unrealized appreciation (depreciation)		(30	)		(8,818	)
Net increase (decrease) in net assets resulting from operations	$	85		$	11,490

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

See accompanying Notes to Financial Statements.

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Statements of Changes in Net Assets

For the Period Ended June 30, 2021 (unaudited) and the Year Ended December 31, 2020 (all amounts in thousands)

	Emerging Markets Debt Fund (a)				Macro Allocation Fund
	2021				2021			2020
*Operations*
Net investment income (loss)		$	96		$	884		$	3,426
Net realized gain (loss) on investments, and other assets and liabilities			19			19,424			(31,014	)
Change in net unrealized appreciation (depreciation) on investments, and other assets and liabilities			(30	)		(8,818	)		(7,205	)
Net increase (decrease) in net assets resulting from operations			85			11,490			(34,793	)
*Distributions to shareholders from*
Class N			—			—			(79	)
Class I			(3	)		—			(2,289	)
Class R6			(85	)		—			(2,567	)
Total distributions			(88	)		—			(4,935	)
*Capital stock transactions*
Proceeds from sale of shares			23,957			10,396			75,968
Shares issued in reinvestment of income dividends and capital gain distributions			88			—			4,686
Less cost of shares redeemed			(17	)		(155,160	)		(438,011	)
Net increase (decrease) in net assets resulting from capital share transactions			24,028			(144,764	)		(357,357	)
Increase (decrease) in net assets			24,025			(133,274	)		(397,085	)
*Net assets*
Beginning of period			—			353,715			750,800
End of period		$	24,025		$	220,441		$	353,715

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

See accompanying Notes to Financial Statements.

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Notes to Financial Statements (information as of June 30, 2021 is unaudited)

(1) Organization

(a) Description of the Trust

William Blair Funds (the “Trust”) is a Delaware statutory trust registered under the Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management investment company. As of the date of this report, the Trust has the following twenty funds (the “Funds”) available for sale, each with its own investment objective and policies. For each Fund, the number of shares authorized is unlimited.

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

(b) Share Classes

Each Fund is comprised of Class N, Class I and Class R6 shares, except the Small-Mid Cap Core and Emerging Markets Debt Funds, which are comprised of Class I and Class R6 shares, and Institutional International Growth Fund, which does not offer multiple classes of shares.

Class N shares 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 in Note 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 I shares 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 R6 shares 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.

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

Class R6 shares 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

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Notes to Financial Statements (information as of June 30, 2021 is unaudited)

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.
Emerging Markets Debt Fund	Provide attractive risk-adjusted returns relative to the Fund’s benchmark through investments in hard currency denominated debt issued in emerging market countries.
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, Emerging Markets Debt and Macro Allocation Funds were the rates in effect on June 30, 2021. Put bonds may be redeemed at the discretion of the holder on specified dates prior to maturity.

Premiums and discounts are amortized and accreted, respectively, 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, 2021, the Bond, Income and Low Duration Funds recognized a reduction of interest income and a corresponding increase in net realized gain of $1,987, $420 and $1,237, 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.

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

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125

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

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 and Emerging Markets Debt Fund are declared daily and paid monthly. Capital gain distributions, if any, for all Funds, are declared and paid at least annually in December and/or January. 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 evaluates tax positions taken or expected to be taken in the course of preparing the Funds’ tax returns to determine whether it is “more likely than not” that each tax position would be sustained upon examination by a taxing authority based on the technical merits of the positions. Tax positions not deemed to meet the “more likely than not” threshold would be recorded as a tax benefit or expense in the current year. 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.

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June 30, 2021

Notes to Financial Statements (information as of June 30, 2021 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 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, 2021, were as follows (in thousands):

							Net
			Gross		Gross		Unrealized
	Cost of		Unrealized		Unrealized		Appreciation/
Fund	Investments		Appreciation		Depreciation		(Depreciation)
Growth	$	169,987	$	157,279	$	658	$	156,621
Large Cap Growth		519,831		298,206		—		298,206
Mid Cap Growth		61,449		26,360		907		25,453
Small-Mid Cap Core		40,051		11,301		270		11,031
Small-Mid Cap Growth		2,373,128		1,105,807		36,093		1,069,714
Small Cap Growth		525,992		224,483		10,550		213,933
Small Cap Value		32,789		15,923		252		15,671
Global Leaders		74,025		64,456		138		64,318
International Leaders		829,546		385,454		18,556		366,898
International Growth		1,369,962		1,000,370		27,174		973,196
Institutional International Growth		767,708		559,340		14,729		544,611
International Small Cap Growth		279,081		89,857		11,241		78,616
Emerging Markets Leaders		267,512		79,207		2,659		76,548
Emerging Markets Growth		837,262		429,589		6,296		423,293
Emerging Markets Small Cap Growth		390,774		110,665		4,103		106,562
Bond		320,911		17,205		2,973		14,232
Income		51,101		897		138		759
Low Duration		139,422		1,269		749		520
Emerging Markets Debt		24,427		212		221		(9	)
Macro Allocation		176,004		48,252		3,678		44,574

As of December 31, 2020, 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, 2020, and the capital loss carryforwards utilized by the Funds in 2020:

	Available Capital Loss Carryforwards						Capital Loss Carryforwards
Fund	Short Term		Long Term		Total		Utilized in 2020
Small-Mid Cap Core	$	12,855	$	51	$	12,906	$	—
Small Cap Value		13,368		—		13,368		—
International Growth		—		—		—		8,604
Institutional International Growth		—		—		—		33,252
International Small Cap Growth		—		—		—		15,355
Emerging Markets Small Cap Growth		—		—		—		46,476
Bond		9,761		10,043		19,804		523
Income		2,596		4,313		6,909		—
Low Duration		13,806		15,977		29,783		—
Macro Allocation		224,668		11,978		236,646		—

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, 2020. Qualified late year ordinary losses are comprised of losses related to swaps, foreign currency and PFICs incurred between November 1 and the end of their fiscal year, December 31, 2020.

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127

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

As of December 31, 2020, the following Funds deferred, on a tax basis, qualified late year losses of (in thousands):

	Qualified Late Year Losses
	Ordinary		Net
Fund	Income		Capital
Emerging Markets Small Cap Growth	$	102	$	—
Bond		741		—
Income		228		—

(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. 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 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.

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Notes to Financial Statements (information as of June 30, 2021 is unaudited)

(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, 2021, the Small-Mid Cap Growth Fund redeemed $224,500 (in thousands) of Fund shares in-kind rather than with cash and recognized net realized gains of $89,621 (in thousands) on the securities distributed to shareholders.

(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.

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, 2021, 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 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.

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William Blair Funds

129

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

(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.

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, non-U.S. bonds and commercial paper 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.

Repurchase Agreements

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

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Notes to Financial Statements (information as of June 30, 2021 is unaudited)

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.

As of June 30, 2021, the value of investments in securities and other financial instruments, segregated by their hierarchical input levels used in determining fair value and by security class or other financial instruments, are shown below (in thousands).

			Large Cap		Mid Cap		Small-Mid
Investments in securities	Growth		Growth		Growth		Cap Core
Level 1—Quoted prices
Common Stocks	$	321,589	$	811,586	$	83,678	$	50,321
Level 2—Other significant observable inputs
Repurchase Agreements		5,019		6,451		3,224		761
Level 3—Significant unobservable inputs
None		—		—		—		—
Total investments in securities	$	326,608	$	818,037	$	86,902	$	51,082

			Small-Mid		Small Cap		Small Cap
Investments in securities			Cap Growth		Growth		Value
Level 1—Quoted prices
Common Stocks			$	3,431,806	$	728,808	$	47,528
Exchange-Traded Funds				—		7,596		—
Level 2—Other significant observable inputs
Repurchase Agreements				11,036		3,521		932
Level 3—Significant unobservable inputs
None				—		—		—
Total investments in securities			$	3,442,842	$	739,925	$	48,460

	Global		International		International		Institutional International
Investments in securities	Leaders		Leaders		Growth		Growth
Level 1—Quoted prices
Common Stocks	$	136,752	$	1,180,151	$	2,326,007	$	1,302,794
Level 2—Other significant observable inputs
Common Stocks		—		—		3,146		1,762
Repurchase Agreements		1,591		16,293		14,005		7,763
Level 3—Significant unobservable inputs
None		—		—		—		—
Total investments in securities	$	138,343	$	1,196,444	$	2,343,158	$	1,312,319

							Emerging
	International		Emerging		Emerging		Markets
	Small Cap		Markets		Markets		Small Cap
Investments in securities	Growth		Leaders		Growth		Growth
Level 1—Quoted prices
Common Stocks	$	350,102	$	314,494	$	1,257,093	$	483,941
Level 2—Other significant observable inputs
Common Stocks		—		—		3,462		10,426
Corporate Obligations		—		19		—		—
Repurchase Agreements		7,595		29,547		—		2,969
Level 3—Significant unobservable inputs
None		—		—		—		—
Total investments in securities	$	357,697	$	344,060	$	1,260,555	$	497,336

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William Blair Funds

131

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

Investments in securities	Bond			Income			Low Duration			Emerging Markets Debt			Macro Allocation
Assets
Level 1—Quoted prices
Exchange-Traded Funds	$	—		$	—		$	—		$	—		$	145,842
Common Stocks		—			—			—			—			10,704
Preferred Stocks		—			—			—			—			954
Level 2—Other significant observable inputs
Asset-Backed Securities		7,146			2,752			15,794			—			—
Commercial Paper		1,100			—			—			—			—
Corporate Obligations		152,704			24,268			51,565			—			—
Foreign Corporate Obligations		—			—			—			7,713			—
Foreign Government Bonds		—			—			—			14,801			27,183
Foreign Municipal Bonds		—			—			—			421			—
Purchased Options		—			—			—			—			561
Repurchase Agreements		291			149			—			1,443			9,466
U.S. Government and U.S. Government Agency		173,902			24,691			72,583			—			21,493
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	$	335,143		$	51,860		$	139,942		$	24,378		$	216,203
Other financial instruments
Assets
Level 1—Quoted prices
Futures Contracts	$	—		$	—		$	—		$	—		$	239
Level 2—Other significant observable inputs
Forward Foreign Currency Contracts		—			—			—			40			5,340
Swaps		—			—			—			43			1,271
Level 3—Significant unobservable inputs
None		—			—			—			—			—
Liabilities
Level 1—Quoted prices
Futures Contracts		—			—			—			—			(3,474	)
Level 2—Other significant observable inputs
Forward Foreign Currency Contracts		—			—			—			—			(3,621	)
Swaps		(42	)		(8	)		—			(65	)		(108	)
U.S. Government Agency		(5,326	)		(1,065	)		(21,080	)		—			—
Level 3—Significant unobservable inputs
None		—			—			—			—			—
Total other financial instruments	$	(5,368	)	$	(1,073	)	$	(21,080	)	$	18		$	(353	)

See Portfolio of Investments for Sector Classification.

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Notes to Financial Statements (information as of June 30, 2021 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 Growth	0.60	%
Mid Cap Growth	0.90	%
Small-Mid Cap Core	0.90	%
Small-Mid Cap Growth	1.00	%
Small Cap Growth	1.10	%
Small Cap Value²	0.75	%

Fixed Income Funds
Bond	0.30	%
Income¹:
First $250 million	0.25	%
In excess of $250 million	0.20	%
Low Duration	0.30	%

Emerging Markets Debt Fund
Emerging Markets Debt	0.65	%

Multi-Asset and Alternative Fund
Macro Allocation	0.80	%

Global Equity Fund
Global Leaders	0.85	%

International Equity Funds
International Leaders	0.85	%
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 March 1, 2021, the Small Cap Value Fund paid a management fee at a rate of 0.95% of the Fund’s average daily net assets. Effective March 1, 2021, the management fee paid to the Adviser was reduced to 0.75%.

June 30, 2021

William Blair Funds

133

Notes to Financial Statements (information as of June 30, 2021 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, 2022. Excluded expenses include interest expenses, taxes, brokerage commissions, acquired fund fees and expenses, dividend and interest expenses on short sales, other investment-related costs and extraordinary expenses, such as litigation and other expenses not incurred in the ordinary course of a Fund’s business. 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						Institutional/Class R6
	Effective			Effective			Effective			Effective			Effective			Effective
	May 1, 2021			May 1, 2020			May 1, 2021			May 1, 2020			May 1, 2021			May 1, 2020
	through			through			through			through			through			through
	April 30,			April 30,			April 30,			April 30,			April 30,			April 30,
Fund	2022			2021			2022			2021			2022			2021
Growth		1.20	%		1.20	%		0.95	%		0.95	%		0.90	%		0.90	%
Large Cap Growth		0.90	%		0.90	%		0.65	%		0.65	%		0.60	%		0.60	%
Mid Cap Growth		1.20	%		1.20	%		0.95	%		0.95	%		0.90	%		0.90	%
Small-Mid Cap Core		N/A			N/A			0.95	%		0.95	%		0.90	%		0.90	%
Small-Mid Cap Growth		1.35	%		1.35	%		1.10	%		1.10	%		1.05	%		1.05	%
Small Cap Growth		1.50	%		1.50	%		1.25	%		1.25	%		1.20	%		1.20	%
Small Cap Value		1.15	%²		1.25	%¹		0.89	%²		1.00	%¹		0.85	%²		0.95	%¹
Global Leaders		1.15	%		1.15	%		0.90	%		0.90	%		0.85	%		0.85	%
International Leaders		1.15	%		1.15	%		0.90	%		0.90	%		0.85	%		0.85	%
International Growth		1.45	%		1.45	%		1.20	%		1.20	%		1.15	%		1.15	%
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	%		1.40	%		1.15	%		1.15	%		1.10	%		1.10	%
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	%		0.65	%
Low Duration		0.55	%		0.55	%		0.40	%		0.40	%		0.35	%		0.35	%
Emerging Markets Debt		N/A			N/A			0.70	%³		N/A			0.65	%³		N/A
Macro Allocation		1.25	%		1.25	%		1.00	%		1.00	%		0.95	%		0.95	%

1	Effective May 1, 2020 through February 28, 2021.
2	Effective March 1, 2021 through April 30, 2023.
3	Effective May 25, 2021 (Commencement of Operations).

The fee waivers and/or expense reimbursements received by each class are reported in the Statements of Operations.

The Adviser is entitled to recoupment of previously waived fees and reimbursed expenses for a period of three years subsequent to a fund’s commencement of operations to the extent that such recoupment does not cause the fund’s annual operating expenses (after the recoupment is taken into account) to exceed both (1) the expense limit in place when such amounts were waived or reimbursed and (2) the fund’s current expense limitation. The total amounts available for recoupment as of June 30, 2021 were as follows (in thousands):

Fund		Available for Recoupment		Expiration of Recoupment
Small-Mid Cap Core	$501		October 1, 2022
Emerging Markets Debt	20		May 25, 2024

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(b) Underwriting and Distribution Services 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 Small-Mid Cap Core, Emerging Markets Debt and Institutional International Growth Funds, 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.

(5) Investment Transactions

Investment transactions, excluding U.S. government securities and short-term securities, for the period ended June 30, 2021, were as follows (in thousands):

Fund	Purchases		Sales
Growth	$	40,171	$	53,968
Large Cap Growth		131,446		127,820
Mid Cap Growth		18,616		19,351
Small-Mid Cap Core		23,810		9,027
Small-Mid Cap Growth		704,598		890,321
Small Cap Growth		190,252		208,292
Small Cap Value		5,540		25,564
Global Leaders		12,469		9,345
International Leaders		165,908		137,945
International Growth		363,749		523,048
Institutional International Growth		202,271		321,051
International Small Cap Growth		108,210		114,566
Emerging Markets Leaders		123,569		80,504
Emerging Markets Growth		379,818		423,906
Emerging Markets Small Cap Growth		296,183		156,463
Bond		97,991		65,995
Income		19,523		31,952
Low Duration		165,772		124,360
Emerging Markets Debt(a)		26,635		3,782
Macro Allocation		58,322		170,090

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

Investment transactions in U.S. government securities, excluding short-term securities, for the period ended June 30, 2021, were as follows (in thousands):

Fund	Purchases		Sales
Bond	$	9,071	$	501
Income		1,378		675
Low Duration		2,000		12,234
Macro Allocation		—		—

(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. The Macro Allocation Fund may also use derivative instruments to implement its investment strategy and obtain desired investment exposures, including by taking long or short positions indirectly through derivative instruments such as, but not limited to, futures, swaps, options and forward

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foreign currency contracts. Such long and short positions may be intended to enhance expected return, reduce expected risk, or both. For additional information regarding the asset class exposures the Macro Allocation Fund typically seeks through futures, swaps, options and forward foreign currency contracts, see the Fund’s principal investment strategy disclosure in its prospectus. The derivative instruments held as of June 30, 2021, as disclosed in each Fund’s Portfolios of Investments, are representative of each Fund’s derivative instrument trading activity during the year ended June 30, 2021.

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.

The 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 the Macro Allocation Fund with various counterparties and allow the 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, Emerging Markets Debt 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 the forward rates at the reporting date, is included in the Statement of Assets and Liabilities as

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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. Under current regulatory requirements, 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 entity, to the receiver for the floating rate, which is the realized variance price of the reference entity. At the time the trade is

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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, 2021, 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⁽¹⁾

—

Payable for variation margin on centrally cleared swaps⁽¹⁾

Income

Credit

Receivable for variation margin on centrally cleared swaps⁽¹⁾

—

Payable for variation margin on centrally cleared swaps⁽¹⁾

Emerging Markets Debt

Credit

Receivable for variation margin on centrally cleared swaps⁽¹⁾

—

Payable for variation margin on centrally cleared swaps⁽¹⁾

Currency

Unrealized appreciation on forward foreign currency contracts

Unrealized depreciation on forward foreign currency contracts)

—

Interest rate

Receivable for variation margin on centrally cleared swaps⁽¹⁾

Payable for variation margin on centrally cleared swaps⁽¹⁾

Macro Allocation

Currency

Unrealized appreciation on forward foreign currency contracts

5,340

Unrealized depreciation on forward foreign currency contracts

3,621

Currency

Investments in securities, at value

237

Options written, at value

—

Equity

Receivable for futures variation margin⁽¹⁾

239

Payable for futures variation margin⁽¹⁾

3,437

Equity

Investments in securities, at value

324

Options written, at value

—

Equity

Unrealized appreciation on swap contracts

1,241

Unrealized depreciation on swap contracts

Interest rate

Unrealized appreciation on swap contracts

Unrealized depreciation on swap contracts

Interest rate

Receivable for futures variation margin⁽¹⁾

—

Payable for futures variation margin⁽¹⁾

Interest rate

Receivable for variation margin on centrally cleared swaps⁽¹⁾

Payable for variation margin on centrally cleared swaps⁽¹⁾

⁽¹⁾

The table above includes cumulative appreciation/(depreciation) on futures contracts and centrally cleared swaps as reported in the applicable Fund’s Portfolio of Investments. Receivable/payable for variation margin on futures contracts and centrally cleared swaps as reported in the applicable Fund’s Statement of Assets and Liabilities represents the current day’s variation margin.

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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, 2021 (in thousands):

	Net 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	$	(1,427	)	Swaps	$	836
Income
Credit	Swaps		(460	)	Swaps		316
Emerging Markets Debt
Credit	Swaps		—		Swaps		(3	)
Currency	Forward foreign currency contracts		4		Forward foreign currency contracts		40
Interest rate	Swaps		(3	)	Swaps		(19	)
Macro Allocation
Credit	Swaps		76		Swaps		(43	)
Currency	Forward foreign currency contracts		(1,304	)	Forward foreign currency contracts		907
Currency	Options		—		Options		54
Equity	Futures contracts		(19,015	)	Futures contracts		2,824
Equity	Options		292		Options		66
Equity	Swaps		923		Swaps		930
Interest rate	Futures contracts		428		Futures contracts		(20	)
Interest rate	Swaps		(1,264	)	Swaps		(296	)

The following table is a summary by counterparty of the derivative instruments and collateral pledged/(received) included in the Fund’s Statement of Assets and Liabilities at June 30, 2021 (in thousands):

	Financial Derivative Assets								Financial Derivative Liabilities
Counterparty	Forward Foreign Currency Contracts		Purchased Options		Swaps		Total		Forward Foreign Currency Contracts			Swaps			Total			Net Market Value			Collateral Pledged (Received)			Net Exposure
Macro Allocation
Citibank N.A.	$	5,340	$	237	$	—	$	5,577	$	(3,621	)	$	—		$	(3,621	)	$	1,956		$	(1,956	)⁽¹⁾	$	—
Credit Suisse		—		324	��	1,251		1,575		—			(90	)		(90	)		1,485			(1,200	)		285
Goldman Sachs		—		—		—		—		—			(4	)		(4	)		(4	)		—			(4	)
	$	5,340	$	561	$	1,251	$	7,152	$	(3,621	)	$	(94	)	$	(3,715	)

Emerging Markets Debt
Citibank N.A.	$	40	$	—	$	—	$	40	$	—		$	—		$	—		$	40		$	—		$	40
	$	40	$	—	$	—	$	40	$	—		$	—		$	—

⁽¹⁾	Does not include additional cash collateral received in the amount of $14 (in thousands).

The net exposure represents the amount due from/(due to) 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.

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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, 2021 (in thousands):

																Class N
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	1,012	$	—	$	6,367	$	(5,355	)		85		—		542		(457	)
Large Cap Growth		26,518		—		20,763		5,755			1,279		—		1,002		277
Mid Cap Growth		151		—		800		(649	)		12		—		62		(50	)
Small-Mid Cap Growth		25,254		—		96,476		(71,222	)		724		—		2,766		(2,042	)
Small Cap Growth		18,718		—		30,411		(11,693	)		492		—		814		(322	)
Small Cap Value		4,131		—		1,861		2,270			263		—		123		140
Global Leaders		169		—		379		(210	)		10		—		21		(11	)
International Leaders		19,182		—		5,131		14,051			820		—		220		600
International Growth		4,627		—		16,582		(11,955	)		115		—		414		(299	)
International Small Cap Growth		60		—		178		(118	)		3		—		10		(7	)
Emerging Markets Leaders		2,378		—		1,994		384			170		—		144		26
Emerging Markets Growth		25,969		—		10,873		15,096			1,314		—		563		751
Emerging Markets Small Cap Growth		109		—		323		(214	)		5		—		14		(9	)
Bond		7,697		530		7,556		671			729		50		721		58
Income		2,213		187		7,435		(5,035	)		257		22		866		(587	)
Low Duration		10,027		154		7,648		2,533			1,164		18		889		293
Macro Allocation		618		—		1,435		(817	)		56		—		130		(74	)

																Class I
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	9,234	$	—	$	12,830	$	(3,596	)		631		—		897		(266	)
Large Cap Growth		74,022		—		73,409		613			3,362		—		3,325		37
Mid Cap Growth		4,437		—		4,822		(385	)		311		—		337		(26	)
Small-Mid Cap Core		5,506		—		2,232		3,274			373		—		154		219
Small-Mid Cap Growth		303,305		—		805,605		(502,300	)		8,151		—		21,686		(13,535	)
Small Cap Growth		46,414		—		58,249		(11,835	)		1,079		—		1,362		(283	)
Small Cap Value		1,482		—		23,538		(22,056	)		95		—		1,588		(1,493	)
Global Leaders		5,977		—		4,025		1,952			322		—		221		101
International Leaders		176,551		—		87,933		88,618			7,472		—		3,645		3,827
International Growth		40,154		—		220,204		(180,050	)		977		—		5,327		(4,350	)
International Small Cap Growth		10,366		—		19,055		(8,689	)		577		—		1,053		(476	)
Emerging Markets Leaders		9,268		—		18,088		(8,820	)		666		—		1,323		(657	)
Emerging Markets Growth		98,212		—		31,397		66,815			4,973		—		1,591		3,382
Emerging Markets Small Cap Growth		15,361		—		19,819		(4,458	)		643		—		849		(206	)
Bond		48,256		2,707		31,060		19,903			4,634		260		2,988		1,906
Income		6,973		380		17,617		(10,264	)		817		44		2,064		(1,203	)
Low Duration		38,885		1,121		41,014		(1,008	)		4,515		131		4,777		(131	)
Emerging Markets Debt (a)		1,151		3		3		1,151			115		—		—		115
Macro Allocation		9,378		—		90,151		(80,773	)		854		—		8,212		(7,358	)

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

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														Institutional/Class R6
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	895	$	—	$	1,061	$	(166	)		62		—		73		(11	)
Large Cap Growth		49,322		—		52,044		(2,722	)		2,220		—		2,382		(162	)
Mid Cap Growth		—		—		—		—			—		—		—		—
Small-Mid Cap Core		11,617		—		80		11,537			795		—		5		790
Small-Mid Cap Growth		216,785		—		20,652		196,133			5,719		—		556		5,163
Small Cap Growth		11,164		—		4,706		6,458			263		—		110		153
Small Cap Value		748		—		1,181		(433	)		47		—		76		(29	)
Global Leaders		1,407		—		—		1,407			81		—		—		81
International Leaders		35,835		—		116,145		(80,310	)		1,554		—		4,912		(3,358	)
International Growth		53,949		—		9,730		44,219			1,281		—		239		1,042
Institutional International Growth		29,938		—		144,198		(114,260	)		1,425		—		6,855		(5,430	)
International Small Cap Growth		18,786		—		3,787		14,999			998		—		208		790
Emerging Markets Leaders		110,565		—		56,917		53,648			7,955		—		4,122		3,833
Emerging Markets Growth		86,298		—		225,987		(139,689	)		4,279		—		11,402		(7,123	)
Emerging Markets Small Cap Growth		158,292		—		15,589		142,703			6,394		—		644		5,750
Bond		3,397		712		1,633		2,476			325		68		157		236
Income		119		1		—		120			14		—		—		14
Low Duration		7,285		282		25,211		(17,644	)		849		33		2,938		(2,056	)
Emerging Markets Debt (a)		22,806		85		14		22,877			2,281		8		1		2,288
Macro Allocation		400		—		63,574		(63,174	)		37		—		5,671		(5,634	)

						Net Change in Net Assets Relating to Fund Share Activity
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	11,141	$	—	$	20,258	$	(9,117	)		778		—		1,512		(734	)
Large Cap Growth		149,862		—		146,216		3,646			6,861		—		6,709		152
Mid Cap Growth		4,588		—		5,622		(1,034	)		323		—		399		(76	)
Small-Mid Cap Core		17,123		—		2,312		14,811			1,168		—		159		1,009
Small-Mid Cap Growth		545,344		—		922,733		(377,389	)		14,594		—		25,008		(10,414	)
Small Cap Growth		76,296		—		93,366		(17,070	)		1,834		—		2,286		(452	)
Small Cap Value		6,361		—		26,580		(20,219	)		405		—		1,787		(1,382	)
Global Leaders		7,553		—		4,404		3,149			413		—		242		171
International Leaders		231,568		—		209,209		22,359			9,846		—		8,777		1,069
International Growth		98,730		—		246,516		(147,786	)		2,373		—		5,980		(3,607	)
Institutional International Growth		29,938		—		144,198		(114,260	)		1,425		—		6,855		(5,430	)
International Small Cap Growth		29,212		—		23,020		6,192			1,578		—		1,271		307
Emerging Markets Leaders		122,211		—		76,999		45,212			8,791		—		5,589		3,202
Emerging Markets Growth		210,479		—		268,257		(57,778	)		10,566		—		13,556		(2,990	)
Emerging Markets Small Cap Growth		173,762		—		35,731		138,031			7,042		—		1,507		5,535
Bond		59,350		3,949		40,249		23,050			5,688		378		3,866		2,200
Income		9,305		568		25,052		(15,179	)		1,088		66		2,930		(1,776	)
Low Duration		56,197		1,557		73,873		(16,119	)		6,528		182		8,604		(1,894	)
Emerging Markets Debt (a)		23,957		88		17		24,028			2,396		8		1		2,403
Macro Allocation		10,396		—		155,160		(144,764	)		947		—		14,013		(13,066	)

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.

June 30, 2021

William Blair Funds

141

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

The following tables summarize the activity in capital shares of each Fund for the year ended December 31, 2020 (in thousands):

																Class N
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	2,054	$	4,719	$	9,133	$	(2,360	)		199		428		907		(280	)
Large Cap Growth		103,916		5,098		72,994		36,020			6,564		257		4,199		2,622
Mid Cap Growth		580		436		1,290		(274	)		58		34		118		(26	)
Small-Mid Cap Growth		52,389		5,571		146,798		(88,838	)		2,096		172		5,868		(3,600	)
Small Cap Growth		33,285		18,183		79,823		(28,355	)		1,253		536		3,063		(1,274	)
Small Cap Value		1,442		2,112		5,248		(1,694	)		132		176		465		(157	)
Global Leaders		1,294		1,318		1,082		1,530			79		76		71		84
International Leaders		13,189		140		7,585		5,744			660		6		420		246
International Growth		35,689		2,302		270,854		(232,863	)		1,431		60		10,703		(9,212	)
International Small Cap Growth		156		57		1,156		(943	)		12		3		101		(86	)
Emerging Markets Leaders		4,442		16		4,880		(422	)		432		1		474		(41	)
Emerging Markets Growth		11,134		382		3,715		7,801			677		21		259		439
Emerging Markets Small Cap Growth		97		—		1,036		(939	)		5		—		67		(62	)
Bond		17,987		1,085		12,752		6,320			1,685		102		1,228		559
Income		9,681		538		7,582		2,637			1,117		62		875		304
Low Duration		21,451		185		9,322		12,314			2,468		21		1,074		1,415
Macro Allocation		1,054		78		6,566		(5,434	)		97		7		602		(498	)

																Class I
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	14,750	$	26,685	$	54,977	$	(13,542	)		1,235		1,980		4,530		(1,315	)
Large Cap Growth		219,016		11,860		185,086		45,790			12,682		563		9,216		4,029
Mid Cap Growth		10,548		5,059		17,687		(2,080	)		885		363		1,472		(224	)
Small-Mid Cap Core		265,306		—		236,282		29,024			24,899		—		23,271		1,628
Small-Mid Cap Growth		704,716		50,709		850,114		(94,689	)		25,299		1,466		31,213		(4,448	)
Small Cap Growth		53,293		34,928		185,988		(97,767	)		1,750		902		6,319		(3,667	)
Small Cap Value		13,215		25,566		100,768		(61,987	)		1,144		2,043		9,063		(5,876	)
Global Leaders		12,040		12,211		46,586		(22,335	)		853		705		3,092		(1,534	)
International Leaders		216,096		2,810		68,924		149,982			10,917		125		3,796		7,246
International Growth		272,612		19,944		417,516		(124,960	)		10,406		512		13,740		(2,822	)
International Small Cap Growth		23,282		2,718		51,685		(25,685	)		1,680		158		3,837		(1,999	)
Emerging Markets Leaders		15,739		590		10,915		5,414			1,480		45		1,115		410
Emerging Markets Growth		28,566		4,194		18,435		14,325			1,793		230		1,249		774
Emerging Markets Small Cap Growth		17,451		62		44,837		(27,324	)		1,057		3		2,759		(1,699	)
Bond		71,936		5,973		59,078		18,831			6,799		567		5,669		1,697
Income		23,843		930		11,163		13,610			2,754		108		1,297		1,565
Low Duration		111,572		1,820		46,902		66,490			12,854		210		5,414		7,650
Macro Allocation		46,704		2,087		218,856		(170,065	)		4,300		192		20,335		(15,843	)

142

Semiannual Report

June 30, 2021

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

														Institutional/Class R6
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	11,384	$	1,332	$	1,426	$	11,290			868		99		105		862
Large Cap Growth		171,386		5,663		4,494		172,555			8,196		269		225		8,240
Mid Cap Growth		361		42		—		403			29		3		—		32
Small-Mid Cap Core		901		—		43		858			93		—		5		88
Small-Mid Cap Growth		72,243		1,722		15,219		58,746			2,470		50		497		2,023
Small Cap Growth		27,131		8,907		15,142		20,896			748		230		466		512
Small Cap Value		8,341		200		599		7,942			758		16		51		723
Global Leaders		3,767		323		50,716		(46,626	)		263		19		3,336		(3,054	)
International Leaders		161,317		5,704		68,132		98,889			8,186		253		3,738		4,701
International Growth		37,075		1,007		12,279		25,803			1,104		26		414		716
Institutional International Growth		148,064		150,369		1,102,278		(803,845	)		8,792		7,511		60,324		(44,021	)
International Small Cap Growth		19,209		3,641		35,644		(12,794	)		1,297		210		2,453		(946	)
Emerging Markets Leaders		40,847		2,293		78,532		(35,392	)		3,598		175		7,041		(3,268	)
Emerging Markets Growth		278,462		39,570		225,547		92,485			18,092		2,152		14,653		5,591
Emerging Markets Small Cap Growth		54,151		129		71,930		(17,650	)		3,232		6		4,178		(940	)
Bond		5,988		1,653		4,616		3,025			568		157		437		288
Income		16		2		—		18			2		—		—		2
Low Duration		33,079		644		29,885		3,838			3,815		74		3,442		447
Macro Allocation		28,210		2,521		212,589		(181,858	)		2,528		232		19,934		(17,174	)

						Net Change in Net Assets Relating to Fund Share Activity
							Dollars									Shares
Fund	Sales		Reinvest		Redemptions		Total			Sales		Reinvest		Redemptions		Total
Growth	$	28,188	$	32,736	$	65,536	$	(4,612	)		2,302		2,507		5,542		(733	)
Large Cap Growth		494,318		22,621		262,574		254,365			27,442		1,089		13,640		14,891
Mid Cap Growth		11,489		5,537		18,977		(1,951	)		972		400		1,590		(218	)
Small-Mid Cap Core		266,207		—		236,325		29,882			24,992		—		23,276		1,716
Small-Mid Cap Growth		829,348		58,002		1,012,131		(124,781	)		29,865		1,688		37,578		(6,025	)
Small Cap Growth		113,709		62,018		280,953		(105,226	)		3,751		1,668		9,848		(4,429	)
Small Cap Value		22,998		27,878		106,615		(55,739	)		2,034		2,235		9,579		(5,310	)
Global Leaders		17,101		13,852		98,384		(67,431	)		1,195		800		6,499		(4,504	)
International Leaders		390,602		8,654		144,641		254,615			19,763		384		7,954		12,193
International Growth		345,376		23,253		700,649		(332,020	)		12,941		598		24,857		(11,318	)
Institutional International Growth		148,064		150,369		1,102,278		(803,845	)		8,792		7,511		60,324		(44,021	)
International Small Cap Growth		42,647		6,416		88,485		(39,422	)		2,989		371		6,391		(3,031	)
Emerging Markets Leaders		61,028		2,899		94,327		(30,400	)		5,510		221		8,630		(2,899	)
Emerging Markets Growth		318,162		44,146		247,697		114,611			20,562		2,403		16,161		6,804
Emerging Markets Small Cap Growth		71,699		191		117,803		(45,913	)		4,294		9		7,004		(2,701	)
Bond		95,911		8,711		76,446		28,176			9,052		826		7,334		2,544
Income		33,540		1,470		18,745		16,265			3,873		170		2,172		1,871
Low Duration		166,102		2,649		86,109		82,642			19,137		305		9,930		9,512
Macro Allocation		75,968		4,686		438,011		(357,357	)		6,925		431		40,871		(33,515	)

June 30, 2021

William Blair Funds

143

Notes to Financial Statements (information as of June 30, 2021 is unaudited)

(8) Subsequent Events

In connection with the Adviser’s acquisition of Investment Counselors of Maryland, LLC (“ICM”), the Board of Trustees of William Blair Funds and the Board of Trustees of The Advisors’ Inner Circle Fund (“AIC”) approved the reorganization of the ICM Small Company Portfolio (“Target Fund”), a series of AIC advised by ICM, into the William Blair Small Cap Value Fund (the “Reorganization”). The Reorganization occurred on July 16, 2021. The Target Fund is the accounting survivor of the Reorganization, and as a result, the William Blair Small Cap Value Fund Class I has adopted the operating and performance history of the ICM Small Company Portfolio for financial reporting purposes. The performance and accounting history for Class N and Class R6 of the reorganized William Blair Small Cap Value Fund begins effective July 19, 2021. The reorganized William Blair Small Cap Value Fund is managed by William V. Heaphy, CFA and Gary J. Merwitz, former employees of ICM, who are employees of the Adviser.

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

144

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	11.15		$	9.45		$	7.91		$	10.27		$	11.41		$	12.52
Income (loss) from investment operations:
Net investment income (loss)			(0.04	)		(0.05	)		(0.03	)		(0.04	)		(0.02	)		(0.02	)
Net realized and unrealized gain (loss) on investments			1.50			3.43			2.54			0.75			2.78			(0.08	)
Total from investment operations			1.46			3.38			2.51			0.71			2.76			(0.10	)
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			1.68			0.97			3.07			3.90			1.01
Total distributions			—			1.68			0.97			3.07			3.90			1.01
Net asset value, end of year		$	12.61		$	11.15		$	9.45		$	7.91		$	10.27		$	11.41
Total return (%)*			13.09			35.97			31.97			5.10			24.35			(0.98	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.22			1.26			1.24			1.22			1.20			1.21
Expenses, net of waivers and reimbursements			1.20			1.20			1.20			1.20			1.20			1.21
Net investment income (loss), before waivers and reimbursements			(0.64	)		(0.55	)		(0.35	)		(0.36	)		(0.14	)		(0.15	)
Net investment income (loss), net of waivers and reimbursements			(0.62	)		(0.49	)		(0.31	)		(0.34	)		(0.14	)		(0.15	)
Class N net assets at the end of the year (in thousands)		$	34,360		$	35,494		$	32,710		$	38,370		$	34,886		$	62,936
Portfolio turnover rate (%)*			13			46			39			46			38			79

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	13.64		$	11.25		$	9.25		$	11.51		$	12.39		$	13.50
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)		(0.03	)		(0.00	)^		(0.01	)		0.02			0.03
Net realized and unrealized gain (loss) on investments			1.83			4.10			2.97			0.82			3.02			(0.10	)
Total from investment operations			1.81			4.07			2.97			0.81			3.04			(0.07	)
Less distributions from:
Net investment income			—			—			—			0.00	^		0.02			0.03
Net realized gain			—			1.68			0.97			3.07			3.90			1.01
Total distributions			—			1.68			0.97			3.07			3.92			1.04
Net asset value, end of year		$	15.45		$	13.64		$	11.25		$	9.25		$	11.51		$	12.39
Total return (%)*			13.27			36.35			32.32			5.42			24.64			(0.69	)
Ratios to average daily net assets (%)**:
Expenses			0.89			0.93			0.92			0.91			0.92			0.90
Net investment income (loss)			(0.31	)		(0.23	)		(0.03	)		(0.06	)		0.12			0.20
Class I net assets at the end of the year (in thousands)		$	278,636		$	249,716		$	220,660		$	187,306		$	318,848		$	514,870
Portfolio turnover rate (%)*			13			46			39			46			38			79

*	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.

June 30, 2021

William Blair Funds

145

Financial Highlights — For a share outstanding throughout each period

Growth Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	13.67			$	11.26		$	11.06
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)			(0.03	)		(0.00	)^
Net realized and unrealized gain (loss) on investments			1.84				4.12			1.17
Total from investment operations			1.82				4.09			1.17
Less distributions from:
Net investment income			—				—			—
Net realized gain			—				1.68			0.97
Total distributions			—				1.68			0.97
Net asset value, end of year		$	15.49			$	13.67		$	11.26
Total return (%)*			13.31				36.50			10.75
Ratios to average daily net assets (%)**:
Expenses			0.84				0.87			0.88
Net investment income (loss)			(0.26	)			(0.23	)		(0.06	)
Class R6 net assets at the end of the year (in thousands)		$	13,471			$	12,041		$	217
Portfolio turnover rate (%)*			13				46			39

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

146

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Large Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	20.03		$	15.27		$	11.99		$	13.35		$	10.26		$	10.15
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)		0.01			0.00	^		(0.02	)		(0.02	)		0.02
Net realized and unrealized gain (loss) on investments			2.86			5.52			4.29			0.81			3.19			0.18
Total from investment operations			2.84			5.53			4.29			0.79			3.17			0.20
Less distributions from:
Net investment income			—			0.00	^		0.01			—			—			0.01
Net realized gain			—			0.77			1.00			2.15			0.08			0.08
Total distributions			—			0.77			1.01			2.15			0.08			0.09
Net asset value, end of year		$	22.87		$	20.03		$	15.27		$	11.99		$	13.35		$	10.26
Total return (%)*			14.18			36.30			36.00			4.96			30.88			1.97
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.05			1.09			1.12			1.21			1.19			1.23
Expenses, net of waivers and reimbursements			0.90			0.90			0.95			1.05			1.05			1.05
Net investment income (loss), before waivers and reimbursements			(0.38	)		(0.15	)		(0.14	)		(0.33	)		(0.27	)		(0.01	)
Net investment income (loss), net of waivers and reimbursements			(0.23	)		0.04			0.03			(0.17	)		(0.13	)		0.17
Class N net assets at the end of the year (in thousands)		$	164,108		$	138,152		$	65,314		$	41,361		$	25,604		$	11,860
Portfolio turnover rate (%)*			17			35			37			47			29			44

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	21.29		$	16.19		$	12.66		$	13.97		$	10.70		$	10.58
Income (loss) from investment operations:
Net investment income (loss)			0.00	^		0.06			0.04			0.01			0.02			0.04
Net realized and unrealized gain (loss) on investments			3.05			5.85			4.54			0.85			3.33			0.19
Total from investment operations			3.05			5.91			4.58			0.86			3.35			0.23
Less distributions from:
Net investment income			—			0.04			0.05			0.02			—			0.03
Net realized gain			—			0.77			1.00			2.15			0.08			0.08
Total distributions			—			0.81			1.05			2.17			0.08			0.11
Net asset value, end of year		$	24.34		$	21.29		$	16.19		$	12.66		$	13.97		$	10.70
Total return (%)*			14.33			36.59			36.35			5.21			31.29			2.22
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.76			0.80			0.81			0.90			0.90			0.91
Expenses, net of waivers and reimbursements			0.65			0.65			0.70			0.80			0.80			0.80
Net investment income (loss), before waivers and reimbursements			(0.09	)		0.16			0.16			(0.01	)		0.03			0.30
Net investment income (loss), net of waivers and reimbursements			0.02			0.31			0.27			0.09			0.13			0.41
Class I net assets at the end of the year (in thousands)		$	455,229		$	397,370		$	236,930		$	137,599		$	177,959		$	110,475
Portfolio turnover rate (%)*			17			35			37			47			29			44

*	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.

June 30, 2021

William Blair Funds

147

Financial Highlights — For a share outstanding throughout each period

Large Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2021			2020			2019(a)
Net asset value, beginning of year		$	21.27		$	16.17		$	15.12
Income (loss) from investment operations:
Net investment income (loss)			0.01			0.01			0.04
Net realized and unrealized gain (loss) on investments			3.04			5.91			2.07
Total from investment operations			3.05			5.92			2.11
Less distributions from:
Net investment income			—			0.05			0.06
Net realized gain			—			0.77			1.00
Total distributions			—			0.82			1.06
Net asset value, end of year		$	24.32		$	21.27		$	16.17
Total return (%)*			14.34			36.70			14.13
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.67			0.70			0.71
Expenses, net of waivers and reimbursements			0.60			0.60			0.60
Net investment income (loss), before waivers and reimbursements			0.01			(0.03	)		0.22
Net investment income (loss), net of waivers and reimbursements			0.08			0.07			0.33
Class R6 net assets at the end of the year (in thousands)		$	198,869		$	177,347		$	1,590
Portfolio turnover rate (%)*			17			35			37

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

148

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Mid Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	12.89		$	10.99		$	8.87		$	10.92		$	10.69		$	11.28
Income (loss) from investment operations:
Net investment income (loss)			(0.05	)		(0.08	)		(0.05	)		(0.06	)		(0.08	)		(0.06	)
Net realized and unrealized gain (loss) on investments			0.51			3.01			3.22			0.03			2.29			0.09
Total from investment operations			0.46			2.93			3.17			(0.03	)		2.21			0.03
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			1.03			1.05			2.02			1.98			0.62
Total distributions			—			1.03			1.05			2.02			1.98			0.62
Net asset value, end of year		$	13.35		$	12.89		$	10.99		$	8.87		$	10.92		$	10.69
Total return (%)*			3.57			26.80			36.02			(1.20	)		20.88			0.23
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.47			1.54			1.51			1.57			1.49			1.45
Expenses, net of waivers and reimbursements			1.20			1.20			1.20			1.23			1.30			1.30
Net investment income (loss), before waivers and reimbursements			(1.09	)		(1.06	)		(0.79	)		(0.85	)		(0.84	)		(0.68	)
Net investment income (loss), net of waivers and reimbursements			(0.82	)		(0.72	)		(0.48	)		(0.51	)		(0.65	)		(0.53	)
Class N net assets at the end of the year (in thousands)		$	5,621		$	6,074		$	5,465		$	4,944		$	6,166		$	16,234
Portfolio turnover rate (%)*			23			45			43			58			59			60

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	14.13		$	11.93		$	9.55		$	11.57		$	11.20		$	11.76
Income (loss) from investment operations:
Net investment income (loss)			(0.04	)		(0.06	)		(0.03	)		(0.03	)		(0.05	)		(0.03	)
Net realized and unrealized gain (loss) on investments			0.55			3.29			3.46			0.03			2.40			0.09
Total from investment operations			0.51			3.23			3.43			—			2.35			0.06
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			1.03			1.05			2.02			1.98			0.62
Total distributions			—			1.03			1.05			2.02			1.98			0.62
Net asset value, end of year		$	14.64		$	14.13		$	11.93		$	9.55		$	11.57		$	11.20
Total return (%)*			3.61			27.21			36.17			(0.86	)		21.18			0.48
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.23			1.29			1.28			1.31			1.23			1.18
Expenses, net of waivers and reimbursements			0.95			0.95			0.95			0.98			1.05			1.05
Net investment income (loss), before waivers and reimbursements			(0.85	)		(0.80	)		(0.56	)		(0.58	)		(0.58	)		(0.39	)
Net investment income (loss), net of waivers and reimbursements			(0.57	)		(0.46	)		(0.23	)		(0.25	)		(0.40	)		(0.26	)
Class I net assets at the end of the year (in thousands)		$	79,711		$	77,273		$	67,936		$	51,173		$	71,369		$	119,424
Portfolio turnover rate (%)*			23			45			43			58			59			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.

June 30, 2021

William Blair Funds

149

Financial Highlights — For a share outstanding throughout each period

Mid Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	14.14			$	11.94		$	11.93
Income (loss) from investment operations:
Net investment income (loss)			(0.04	)			(0.06	)		(0.01	)
Net realized and unrealized gain (loss) on investments			0.56				3.29			1.07
Total from investment operations			0.52				3.23			1.06
Less distributions from:
Net investment income			—				—			—
Net realized gain			—				1.03			1.05
Total distributions			—				1.03			1.05
Net asset value, end of year		$	14.66			$	14.14		$	11.94
Total return (%)*			3.68				27.18			9.10
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.11				1.16			1.14
Expenses, net of waivers and reimbursements			0.90				0.90			0.90
Net investment income (loss), before waivers and reimbursements			(0.73	)			(0.70	)		(0.41	)
Net investment income (loss), net of waivers and reimbursements			(0.52	)			(0.44	)		(0.17	)
Class R6 net assets at the end of the year (in thousands)		$	646			$	623		$	145
Portfolio turnover rate (%)*			23				45			43

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

150

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Small-Mid Cap Core Fund

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	12.88			$	10.68		$	10.00
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)			0.00	^		0.02
Net realized and unrealized gain (loss) on investments			2.37				2.20			0.67
Total from investment operations			2.36				2.20			0.69
Less distributions from:
Net investment income			—				—			0.01
Net realized gain			—				—			—
Total distributions			—				—			0.01
Net asset value, end of year		$	15.24			$	12.88		$	10.68
Total return (%)*			18.32				20.60			6.87
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.46				1.22			3.92
Expenses, net of waivers and reimbursements			0.95				0.95			0.95
Net investment income (loss), before waivers and reimbursements			(0.69	)			(0.27	)		(2.23	)
Net investment income (loss), net of waivers and reimbursements			(0.18	)			0.00			0.74
Class N net assets at the end of the year (in thousands)		$	30,517			$	22,958		$	1,655
Portfolio turnover rate (%)*			23				244			12

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	12.88			$	10.68		$	10.00
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)			0.01			0.01
Net realized and unrealized gain (loss) on investments			2.38				2.19			0.68
Total from investment operations			2.37				2.20			0.69
Less distributions from:
Net investment income			—				0.00	^		0.01
Net realized gain			—				—			—
Total distributions			—				0.00	^		0.01
Net asset value, end of year		$	15.25			$	12.88		$	10.68
Total return (%)*			18.40				20.60			6.88
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.30				1.07			3.92
Expenses, net of waivers and reimbursements			0.90				0.90			0.90
Net investment income (loss), before waivers and reimbursements			(0.50	)			(0.11	)		(2.71	)
Net investment income (loss), net of waivers and reimbursements			(0.10	)			0.06			0.31
Class I net assets at the end of the year (in thousands)		$	20,442			$	7,087		$	4,933
Portfolio turnover rate (%)*			23				244			12

(a)	For the period from October 1, 2019 (Commencement of Operations) to December 31, 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.

June 30, 2021

William Blair Funds

151

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,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	32.96		$	25.41		$	20.97		$	23.36		$	19.20		$	18.53
Income (loss) from investment operations:
Net investment income (loss)			(0.18	)		(0.24	)		(0.20	)		(0.18	)		(0.16	)		(0.09	)
Net realized and unrealized gain (loss) on investments			2.82			8.37			6.56			(0.25	)		5.62			1.29
Total from investment operations			2.64			8.13			6.36			(0.43	)		5.46			1.20
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			0.58			1.92			1.96			1.30			0.53
Total distributions			—			0.58			1.92			1.96			1.30			0.53
Net asset value, end of year		$	35.60		$	32.96		$	25.41		$	20.97		$	23.36		$	19.20
Total return (%)*			8.04			32.04			30.41			(2.29	)		28.57			6.45
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.43			1.45			1.43			1.44			1.43			1.43
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			(1.11	)		(1.01	)		(0.88	)		(0.81	)		(0.82	)		(0.59	)
Net investment income (loss), net of waivers and reimbursements			(1.03	)		(0.91	)		(0.80	)		(0.72	)		(0.74	)		(0.51	)
Class N net assets at the end of the year (in thousands)		$	267,143		$	314,572		$	334,017		$	424,865		$	228,828		$	171,638
Portfolio turnover rate (%)*			20			55			56			46			64			66

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	35.13		$	26.99		$	22.12		$	24.48		$	20.02		$	19.25
Income (loss) from investment operations:
Net investment income (loss)			(0.14	)		(0.19	)		(0.14	)		(0.12	)		(0.11	)		(0.05	)
Net realized and unrealized gain (loss) on investments			3.01			8.91			6.93			(0.28	)		5.87			1.35
Total from investment operations			2.87			8.72			6.79			(0.40	)		5.76			1.30
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			0.58			1.92			1.96			1.30			0.53
Total distributions			—			0.58			1.92			1.96			1.30			0.53
Net asset value, end of year		$	38.00		$	35.13		$	26.99		$	22.12		$	24.48		$	20.02
Total return (%)*			8.17			32.35			30.77			(2.06	)		28.90			6.72
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.16			1.17			1.16			1.16			1.16			1.16
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			(0.84	)		(0.73	)		(0.59	)		(0.53	)		(0.55	)		(0.34	)
Net investment income (loss), net of waivers and reimbursements			(0.78	)		(0.66	)		(0.53	)		(0.47	)		(0.49	)		(0.28	)
Class I net assets at the end of the year (in thousands)		$	2,881,276		$	3,139,290		$	2,531,823		$	1,979,105		$	1,576,180		$	1,090,939
Portfolio turnover rate (%)*			20			55			56			46			64			66

*	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.

152

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Small-Mid Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	35.18			$	27.01		$	26.76
Income (loss) from investment operations:
Net investment income (loss)			(0.13	)			(0.17	)		(0.09	)
Net realized and unrealized gain (loss) on investments			3.01				8.92			2.26
Total from investment operations			2.88				8.75			2.17
Less distributions from:
Net investment income			—				—			—
Net realized gain			—				0.58			1.92
Total distributions			—				0.58			1.92
Net asset value, end of year		$	38.06			$	35.18		$	27.01
Total return (%)*			8.19				32.44			8.17
Ratios to average daily net assets (%)**:
Expenses			1.03				1.05			1.05
Net investment income (loss)			(0.68	)			(0.61	)		(0.46	)
Class R6 net assets at the end of the year (in thousands)		$	329,840			$	123,220		$	39,974
Portfolio turnover rate (%)*			20				55			56

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

June 30, 2021

William Blair Funds

153

Financial Highlights — For a share outstanding throughout each period

Small Cap Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	34.49		$	27.75		$	23.23		$	26.87		$	25.24		$	22.47
Income (loss) from investment operations:
Net investment income (loss)			(0.22	)		(0.29	)		(0.24	)		(0.27	)		(0.25	)		(0.18	)
Net realized and unrealized gain (loss) on investments			4.65			10.86			5.40			(0.10	)		6.88			4.43
Total from investment operations			4.43			10.57			5.16			(0.37	)		6.63			4.25
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			3.83			0.64			3.27			5.00			1.48
Total distributions			—			3.83			0.64			3.27			5.00			1.48
Net asset value, end of year		$	38.92		$	34.49		$	27.75		$	23.23		$	26.87		$	25.24
Total return (%)*			12.84			38.32			22.26			(2.14	)		26.70			18.89
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.55			1.58			1.54			1.55			1.54			1.55
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			(1.26	)		(1.10	)		(0.92	)		(0.94	)		(0.93	)		(0.84	)
Net investment income (loss), net of waivers and reimbursements			(1.21	)		(1.02	)		(0.88	)		(0.89	)		(0.89	)		(0.79	)
Class N net assets at the end of the year (in thousands)		$	191,361		$	180,635		$	180,706		$	169,074		$	146,291		$	117,068
Portfolio turnover rate (%)*			27			71			51			74			81			90

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	39.36		$	31.19		$	25.99		$	29.61		$	27.34		$	24.17
Income (loss) from investment operations:
Net investment income (loss)			(0.20	)		(0.24	)		(0.19	)		(0.21	)		(0.20	)		(0.13	)
Net realized and unrealized gain (loss) on investments			5.32			12.24			6.03			(0.14	)		7.47			4.78
Total from investment operations			5.12			12.00			5.84			(0.35	)		7.27			4.65
Less distributions from:
Net investment income			—			—			—			—			—			—
Net realized gain			—			3.83			0.64			3.27			5.00			1.48
Total distributions			—			3.83			0.64			3.27			5.00			1.48
Net asset value, end of year		$	44.48		$	39.36		$	31.19		$	25.99		$	29.61		$	27.34
Total return (%)*			13.01			38.68			22.51			(1.88	)		26.99			19.22
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.25			1.30			1.27			1.25			1.25			1.27
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			(0.95	)		(0.82	)		(0.65	)		(0.65	)		(0.64	)		(0.56	)
Net investment income (loss), net of waivers and reimbursements			(0.95	)		(0.77	)		(0.63	)		(0.65	)		(0.64	)		(0.54	)
Class I net assets at the end of the year (in thousands)		$	428,670		$	390,511		$	423,881		$	410,233		$	343,119		$	271,830
Portfolio turnover rate (%)*			27			71			51			74			81			90

*	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.

154

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Small Cap Growth Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021				2020			2019(a)
Net asset value, beginning of year		$	39.40			$	31.20		$	31.00
Income (loss) from investment operations:
Net investment income (loss)			(0.18	)			(0.23	)		(0.11	)
Net realized and unrealized gain (loss) on investments			5.32				12.26			0.95
Total from investment operations			5.14				12.03			0.84
Less distributions from:
Net investment income			—				—			—
Net realized gain			—				3.83			0.64
Total distributions			—				3.83			0.64
Net asset value, end of year		$	44.54			$	39.40		$	31.20
Total return (%)*			13.05				38.76			2.75
Ratios to average daily net assets (%)**:
Expenses			1.16				1.19			1.18
Net investment income (loss)			(0.86	)			(0.71	)		(0.51	)
Class R6 net assets at the end of the year (in thousands)		$	123,768			$	103,462		$	65,950
Portfolio turnover rate (%)*			27				71			51

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

June 30, 2021

William Blair Funds

155

Financial Highlights — For a share outstanding throughout each period

Small Cap Value Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	13.04		$	17.47		$	15.04	$	20.15		$	20.18		$	16.68
Income (loss) from investment operations:
Net investment income (loss)			0.03			0.08			0.09		0.03			0.01			0.04
Net realized and unrealized gain (loss) on investments			2.27			(1.38	)		2.92		(3.12	)		1.50			4.34
Total from investment operations			2.30			(1.30	)		3.01		(3.09	)		1.51			4.38
Less distributions from:
Net investment income			—			0.05			0.09		—			—			0.04
Net realized gain			—			3.08			0.49		2.02			1.54			0.84
Total distributions			—			3.13			0.58		2.02			1.54			0.88
Net asset value, end of year		$	15.34		$	13.04		$	17.47	$	15.04		$	20.15		$	20.18
Total return (%)*			17.64			(5.76	)		20.09		(15.93	)		7.57			26.19
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.61			1.71			1.55		1.56			1.55			1.53
Expenses, net of waivers and reimbursements			1.18			1.33			1.50		1.50			1.50			1.50
Net investment income (loss), before waivers and reimbursements			(0.05	)		0.26			0.49		0.08			(0.01	)		0.19
Net investment income (loss), net of waivers and reimbursements			0.38			0.64			0.54		0.14			0.04			0.22
Class N net assets at the end of the year (in thousands)		$	10,865		$	7,402		$	12,672	$	16,381		$	29,271		$	33,359
Portfolio turnover rate (%)*			11			64			116		56			38			33

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	13.57		$	18.02		$	15.50	$	20.70		$	20.68		$	17.08
Income (loss) from investment operations:
Net investment income (loss)			0.04			0.11			0.14		0.08			0.06			0.09
Net realized and unrealized gain (loss) on investments			2.38			(1.40	)		3.01		(3.21	)		1.54			4.44
Total from investment operations			2.42			(1.29	)		3.15		(3.13	)		1.60			4.53
Less distributions from:
Net investment income			—			0.08			0.14		0.05			0.04			0.09
Net realized gain			—			3.08			0.49		2.02			1.54			0.84
Total distributions			—			3.16			0.63		2.07			1.58			0.93
Net asset value, end of year		$	15.99		$	13.57		$	18.02	$	15.50		$	20.70		$	20.68
Total return (%)*			17.83			(5.57	)		20.45		(15.74	)		7.85			26.46
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.63			1.48			1.31		1.30			1.29			1.29
Expenses, net of waivers and reimbursements			0.93			1.08			1.25		1.25			1.25			1.25
Net investment income (loss), before waivers and reimbursements			(0.13	)		0.48			0.74		0.36			0.25			0.43
Net investment income (loss), net of waivers and reimbursements			0.57			0.88			0.80		0.41			0.29			0.47
Class I net assets at the end of the year (in thousands)		$	25,982		$	42,311		$	162,093	$	475,134		$	644,749		$	675,272
Portfolio turnover rate (%)*			11			64			116		56			38			33

*	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.

156

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Small Cap Value Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2021			2020			2019(a)
Net asset value, beginning of year		$	13.56		$	18.03		$	18.19
Income (loss) from investment operations:
Net investment income (loss)			0.05			0.12			0.16
Net realized and unrealized gain (loss) on investments			2.37			(1.41	)		0.32
Total from investment operations			2.42			(1.29	)		0.48
Less distributions from:
Net investment income			—			0.10			0.15
Net realized gain			—			3.08			0.49
Total distributions			—			3.18			0.64
Net asset value, end of year		$	15.98		$	13.56		$	18.03
Total return (%)*			17.85			(5.55	)		2.69
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.24			1.30			1.17
Expenses, net of waivers and reimbursements			0.88			1.03			1.17
Net investment income (loss), before waivers and reimbursements			0.27			0.75			1.28
Net investment income (loss), net of waivers and reimbursements			0.63			1.02			1.28
Class R6 net assets at the end of the year (in thousands)		$	11,532		$	10,188		$	513
Portfolio turnover rate (%)*			11			64			116

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

June 30, 2021

William Blair Funds

157

Financial Highlights — For a share outstanding throughout each period

Global Leaders Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017		2016
Net asset value, beginning of year		$	17.41		$	14.92		$	11.47		$	14.53		$	11.60	$	11.58
Income (loss) from investment operations:
Net investment income (loss)			(0.04	)		(0.06	)		0.01			0.02			0.05		0.03
Net realized and unrealized gain (loss) on investments			1.92			4.74			3.61			(1.12	)		3.46		0.04
Total from investment operations			1.88			4.68			3.62			(1.10	)		3.51		0.07
Less distributions from:
Net investment income			—			—			0.03			—			0.10		—
Net realized gain			—			2.19			0.14			1.96			0.48		0.05
Total distributions			—			2.19			0.17			1.96			0.58		0.05
Net asset value, end of year		$	19.29		$	17.41		$	14.92		$	11.47		$	14.53	$	11.60
Total return (%)*			10.80			31.50			31.57			(8.23	)		30.31		0.62
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.40			1.45			1.39			1.47			1.63		1.62
Expenses, net of waivers and reimbursements			1.15			1.15			1.20			1.33			1.37		1.36
Net investment income (loss), before waivers and reimbursements			(0.65	)		(0.67	)		(0.10	)		(0.01	)		0.09		(0.03	)
Net investment income (loss), net of waivers and reimbursements			(0.40	)		(0.37	)		0.09			0.13			0.35		0.23
Class N net assets at the end of the year (in thousands)		$	12,925		$	11,861		$	8,910		$	7,225		$	7,761	$	5,760
Portfolio turnover rate (%)*			7			27			27			49			41		75

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019			2018			2017		2016
Net asset value, beginning of year		$	17.47		$	14.93		$	11.47		$	14.56		$	11.62	$	11.59
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.01	)		0.05			0.06			0.09		0.06
Net realized and unrealized gain (loss) on investments			1.92			4.74			3.61			(1.13	)		3.47		0.05
Total from investment operations			1.91			4.73			3.66			(1.07	)		3.56		0.11
Less distributions from:
Net investment income			—			0.00^			0.06			0.06			0.14		0.03
Net realized gain			—			2.19			0.14			1.96			0.48		0.05
Total distributions			—			2.19			0.20			2.02			0.62		0.08
Net asset value, end of year		$	19.38		$	17.47		$	14.93		$	11.47		$	14.56	$	11.62
Total return (%)*			10.93			31.86			31.96			(8.06	)		30.69		0.98
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.09			1.12			1.07			1.15			1.33		1.31
Expenses, net of waivers and reimbursements			0.90			0.90			0.95			1.07			1.07		1.05
Net investment income (loss), before waivers and reimbursements			(0.34	)		(0.31	)		0.22			0.31			0.39		0.28
Net investment income (loss), net of waivers and reimbursements			(0.15	)		(0.09	)		0.34			0.39			0.65		0.54
Class I net assets at the end of the year (in thousands)		$	121,059		$	107,375		$	114,666		$	83,790		$	60,067	$	45,772
Portfolio turnover rate (%)*			7			27			27			49			41		75

*	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.

158

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Global Leaders Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	17.47		$	14.93		$	11.47	$	14.56		$	11.62	$	11.59
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		0.02			0.06		0.07			0.10		0.07
Net realized and unrealized gain (loss) on investments			1.93			4.72			3.61		(1.13	)		3.47		0.05
Total from investment operations			1.92			4.74			3.67		(1.06	)		3.57		0.12
Less distributions from:
Net investment income			—			0.01			0.07		0.07			0.15		0.04
Net realized gain			—			2.19			0.14		1.96			0.48		0.05
Total distributions			—			2.20			0.21		2.03			0.63		0.09
Net asset value, end of year		$	19.39		$	17.47		$	14.93	$	11.47		$	14.56	$	11.62
Total return (%)*			10.99			31.91			32.02		(7.99	)		30.78		1.03
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.01			1.06			1.01		1.08			1.10		1.11
Expenses, net of waivers and reimbursements			0.85			0.85			0.90		1.00			1.00		1.00
Net investment income (loss), before waivers and reimbursements			(0.22	)		(0.10	)		0.32		0.39			0.65		0.48
Net investment income (loss), net of waivers and reimbursements			(0.06	)		0.11			0.43		0.47			0.75		0.59
Class R6 net assets at the end of the year (in thousands)		$	4,844		$	2,946		$	48,133	$	79,685		$	143,521	$	125,199
Portfolio turnover rate (%)*			7			27			27		49			41		75

*	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.

June 30, 2021

William Blair Funds

159

Financial Highlights — For a share outstanding throughout each period

International Leaders Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	22.69		$	18.08		$	13.80	$	16.37		$	12.88	$	12.89
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)		(0.04	)		0.09		0.13			0.11		0.03
Net realized and unrealized gain (loss) on investments			1.43			4.82			4.25		(2.19	)		3.70		0.08
Total from investment operations			1.41			4.78			4.34		(2.06	)		3.81		0.11
Less distributions from:
Net investment income			—			—			0.06		0.06			0.20		0.12
Net realized gain			—			0.17			—		0.45			0.12		—
Total distributions			—			0.17			0.06		0.51			0.32		0.12
Net asset value, end of year		$	24.10		$	22.69		$	18.08	$	13.80		$	16.37	$	12.88
Total return (%)*			6.21			26.45			31.46		(12.70	)		29.65		0.88
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.27			1.31			1.32		1.39			1.59		1.56
Expenses, net of waivers and reimbursements			1.15			1.15			1.18		1.28			1.35		1.30
Net investment income (loss), before waivers and reimbursements			(0.27	)		(0.39	)		0.44		0.70			0.48		(0.02	)
Net investment income (loss), net of waivers and reimbursements			(0.15	)		(0.23	)		0.58		0.81			0.72		0.24
Class N net assets at the end of the year (in thousands)		$	35,254		$	19,586		$	11,163	$	8,715		$	9,651	$	2,922
Portfolio turnover rate (%)*			12			34			20		33			41		59

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	22.80		$	18.13		$	13.84	$	16.44		$	12.92	$	12.91
Income (loss) from investment operations:
Net investment income (loss)			0.01			(0.00	)^		0.12		0.17			0.16		0.10
Net realized and unrealized gain (loss) on investments			1.43			4.85			4.27		(2.19	)		3.71		0.04
Total from investment operations			1.44			4.85			4.39		(2.02	)		3.87		0.14
Less distributions from:
Net investment income			—			0.01			0.10		0.13			0.23		0.13
Net realized gain			—			0.17			—		0.45			0.12		—
Total distributions			—			0.18			0.10		0.58			0.35		0.13
Net asset value, end of year		$	24.24		$	22.80		$	18.13	$	13.84		$	16.44	$	12.92
Total return (%)*			6.32			26.77			31.76		(12.45	)		30.05		1.10
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.98			1.01			1.01		1.07			1.28		1.30
Expenses, net of waivers and reimbursements			0.90			0.90			0.93		1.03			1.05		1.04
Net investment income (loss), before waivers and reimbursements			(0.02	)		(0.11	)		0.64		1.02			0.86		0.48
Net investment income (loss), net of waivers and reimbursements			0.06			(0.00	)		0.72		1.06			1.09		0.74
Class I net assets at the end of the year (in thousands)		$	511,382		$	393,596		$	181,617	$	76,382		$	60,279	$	30,944
Portfolio turnover rate (%)*			12			34			20		33			41		59

*	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.

160

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

International Leaders Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2021		2020		2019		2018			2017		2016
Net asset value, beginning of year		$	22.80	$	18.12	$	13.83	$	16.43		$	12.92	$	12.90
Income (loss) from investment operations:
Net investment income (loss)			0.01		0.02		0.14		0.18			0.18		0.12
Net realized and unrealized gain (loss) on investments			1.44		4.85		4.26		(2.19	)		3.70		0.04
Total from investment operations			1.45		4.87		4.40		(2.01	)		3.88		0.16
Less distributions from:
Net investment income			—		0.02		0.11		0.14			0.25		0.14
Net realized gain			—		0.17		—		0.45			0.12		—
Total distributions			—		0.19		0.11		0.59			0.37		0.14
Net asset value, end of year		$	24.25	$	22.80	$	18.12	$	13.83		$	16.43	$	12.92
Total return (%)*			6.36		26.88		31.83		(12.38	)		30.08		1.25
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.90		0.92		0.93		0.99			1.03		1.06
Expenses, net of waivers and reimbursements			0.85		0.85		0.88		0.95			0.95		0.95
Net investment income (loss), before waivers and reimbursements			0.02		0.03		0.80		1.07			1.10		0.81
Net investment income (loss), net of waivers and reimbursements			0.07		0.10		0.85		1.11			1.18		0.92
Class R6 net assets at the end of the year (in thousands)		$	649,617	$	687,171	$	461,124	$	324,902		$	308,898	$	221,356
Portfolio turnover rate (%)*			12		34		20		33			41		59

*	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.

June 30, 2021

William Blair Funds

161

Financial Highlights — For a share outstanding throughout each period

International Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	38.75		$	29.68		$	23.04	$	30.41		$	23.86	$	24.94
Income (loss) from investment operations:
Net investment income (loss)			(0.07	)		(0.16	)		0.09		0.16			0.21		0.20
Net realized and unrealized gain (loss) on investments			3.28			9.55			6.87		(5.56	)		6.73		(0.92	)
Total from investment operations			3.21			9.39			6.96		(5.40	)		6.94		(0.72	)
Less distributions from:
Net investment income			—			0.06			0.32		0.12			0.39		0.36
Net realized gain			—			0.26			—		1.85			—		—
Total distributions			—			0.32			0.32		1.97			0.39		0.36
Net asset value, end of year		$	41.96		$	38.75		$	29.68	$	23.04		$	30.41	$	23.86
Total return (%)*			8.28			31.64			30.24		(18.00	)		29.11		(2.88	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.46			1.47			1.45		1.46			1.47		1.43
Expenses, net of waivers and reimbursements			1.45			1.45			1.45		1.45			1.45		1.43
Net investment income (loss), before waivers and reimbursements			(0.34	)		(0.56	)		0.34		0.54			0.76		0.84
Net investment income (loss), net of waivers and reimbursements			(0.33	)		(0.54	)		0.34		0.55			0.78		0.84
Class N net assets at the end of the year (in thousands)		$	300,351		$	288,976		$	494,788	$	456,533		$	763,740	$	729,544
Portfolio turnover rate (%)*			16			27			34		78			82		101

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	39.65		$	30.38		$	23.56	$	31.13		$	24.42	$	25.51
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.08	)		0.18		0.26			0.30		0.29
Net realized and unrealized gain (loss) on investments			3.36			9.79			7.03		(5.70	)		6.89		(0.94	)
Total from investment operations			3.35			9.71			7.21		(5.44	)		7.19		(0.65	)
Less distributions from:
Net investment income			—			0.18			0.39		0.28			0.48		0.44
Net realized gain			—			0.26			—		1.85			—		—
Total distributions			—			0.44			0.39		2.13			0.48		0.44
Net asset value, end of year		$	43.00		$	39.65		$	30.38	$	23.56		$	31.13	$	24.42
Total return (%)*			8.45			31.99			30.66		(17.73	)		29.49		(2.54	)
Ratios to average daily net assets (%)**:
Expenses			1.14			1.16			1.14		1.13			1.14		1.13
Net investment income (loss)			(0.04	)		(0.24	)		0.65		0.86			1.08		1.16
Class I net assets at the end of the year (in thousands)		$	1,888,879		$	1,914,460		$	1,552,355	$	1,646,811		$	2,375,326	$	2,251,701
Portfolio turnover rate (%)*			16			27			34		78			82		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.

162

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

International Growth Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
		2021		2020			2019(a)
Net asset value, beginning of year		$	39.66	$	30.37		$	27.56
Income (loss) from investment operations:
Net investment income (loss)			0.03		(0.07	)		(0.05	)
Net realized and unrealized gain (loss) on investments			3.33		9.83			3.27
Total from investment operations			3.36		9.76			3.22
Less distributions from:
Net investment income			—		0.21			0.41
Net realized gain			—		0.26			—
Total distributions			—		0.47			0.41
Net asset value, end of year		$	43.02	$	39.66		$	30.37
Total return (%)*			8.47		32.16			11.71
Ratios to average daily net assets (%)**:
Expenses			1.06		1.07			1.06
Net investment income (loss)			0.14		(0.23	)		(0.26	)
Class R6 net assets at end of year (in thousands)		$	163,300	$	109,214		$	61,916
Portfolio turnover rate (%)*			16		27			34

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

June 30, 2021

William Blair Funds

163

Financial Highlights — For a share outstanding throughout each period

Institutional International Growth Fund

	Institutional
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	20.37		$	17.35		$	13.40	$	18.08		$	14.55	$	15.08
Income (loss) from investment operations:
Net investment income (loss)			(0.00)	^		(0.01	)		0.12		0.18			0.21		0.18
Net realized and unrealized gain (loss) on investments			1.73			5.60			4.00		(3.29	)		4.07		(0.54	)
Total from investment operations			1.73			5.59			4.12		(3.11	)		4.28		(0.36	)
Less distributions from:
Net investment income			—			0.02			0.17		0.17			0.44		0.17
Net realized gain			—			2.55			—		1.40			0.31		—
Total distributions			—			2.57			0.17		1.57			0.75		0.17
Net asset value, end of year		$	22.10		$	20.37		$	17.35	$	13.40		$	18.08	$	14.55
Total return (%)*			8.49			32.47			30.75		(17.50	)		29.53		(2.40	)
Ratios to average daily net assets (%)**:
Expenses			1.01			1.00			0.99		0.97			0.97		0.98
Net investment income (loss),			(0.02	)		(0.04	)		0.77		1.01			1.22		1.25
Net assets at the end of the year (in thousands)		$	1,318,807		$	1,326,482		$	1,892,911	$	1,784,435		$	2,330,299	$	2,093,971
Portfolio turnover rate (%)*			16			31			35		82			84		105

*	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.

164

Semiannual Report

June 30, 2021

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,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	17.45		$	13.85		$	10.36	$	15.49		$	12.87	$	13.50
Income (loss) from investment operations:
Net investment income (loss)			(0.03	)		(0.05	)		0.05		0.04			0.12		0.10
Net realized and unrealized gain (loss) on investments			1.30			4.01			3.45		(3.78	)		3.98		(0.72	)
Total from investment operations			1.27			3.96			3.50		(3.74	)		4.10		(0.62	)
Less distributions from:
Net investment income			—			—			0.01		0.08			0.32		0.01
Net realized gain			—			0.36			—		1.31			1.16		0.00	^
Total distributions			—			0.36			0.01		1.39			1.48		0.01
Net asset value, end of year		$	18.72		$	17.45		$	13.85	$	10.36		$	15.49	$	12.87
Total return (%)*			7.28			28.68			33.81		(24.48	)		32.17		(4.60	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.47			1.52			1.48		1.48			1.62		1.59
Expenses, net of waivers and reimbursements			1.47			1.52			1.48		1.48			1.47		1.44
Net investment income (loss), before waivers and reimbursements			(0.36	)		(0.36	)		0.45		0.29			0.70		0.62
Net investment income (loss), net of waivers and reimbursements			(0.36	)		(0.36	)		0.45		0.29			0.85		0.77
Class N net assets at the end of the year (in thousands)		$	3,201		$	3,101		$	3,650	$	3,440		$	6,275	$	10,361
Portfolio turnover rate (%)*			32			63			38		88			64		73

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	17.66		$	13.98		$	10.45	$	15.65		$	13.00	$	13.65
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		(0.01	)		0.09		0.09			0.14		0.14
Net realized and unrealized gain (loss) on investments			1.32			4.06			3.48		(3.84	)		4.07		(0.75	)
Total from investment operations			1.31			4.05			3.57		(3.75	)		4.21		(0.61	)
Less distributions from:
Net investment income			—			0.01			0.04		0.14			0.40		0.04
Net realized gain			—			0.36			—		1.31			1.16		0.00	^
Total distributions			—			0.37			0.04		1.45			1.56		0.04
Net asset value, end of year		$	18.97		$	17.66		$	13.98	$	10.45		$	15.65	$	13.00
Total return (%)*			7.42			29.04			34.22		(24.29	)		32.70		(4.41	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.20			1.25			1.21		1.18			1.31		1.30
Expenses, net of waivers and reimbursements			1.20			1.25			1.21		1.18			1.16		1.15
Net investment income (loss), before waivers and reimbursements			(0.09	)		(0.05	)		0.75		0.60			0.77		0.91
Net investment income (loss), net of waivers and reimbursements			(0.09	)		(0.05	)		0.75		0.60			0.92		1.06
Class I net assets at the end of the year (in thousands)		$	147,051		$	145,283		$	142,951	$	165,451		$	338,920	$	306,526
Portfolio turnover rate (%)*			32			63			38		88			64		73

*	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.

June 30, 2021

William Blair Funds

165

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,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	17.76		$	14.05		$	10.50	$	15.73		$	13.07	$	13.72
Income (loss) from investment operations:
Net investment income (loss)			0.00	^		0.00	^		0.11		0.10			0.15		0.15
Net realized and unrealized gain (loss) on investments			1.33			4.09			3.49		(3.85	)		4.08		(0.74	)
Total from investment operations			1.33			4.09			3.60		(3.75	)		4.23		(0.59	)
Less distributions from:
Net investment income			—			0.02			0.05		0.17			0.41		0.06
Net realized gain			—			0.36			—		1.31			1.16		0.00	^
Total distributions			—			0.38			0.05		1.48			1.57		0.06
Net asset value, end of year		$	19.09		$	17.76		$	14.05	$	10.50		$	15.73	$	13.07
Total return (%)*			7.49			29.23			34.32		(24.19	)		32.70		(4.31	)
Ratios to average daily net assets (%)**:
Expenses			1.11			1.14			1.12		1.08			1.08		1.07
Net investment income (loss)			0.02			0.02			0.86		0.67			0.99		1.13
Class R6 net assets at the end of the year (in thousands)		$	217,688		$	188,497		$	162,465	$	171,833		$	256,558	$	199,746
Portfolio turnover rate (%)*			32			63			38		88			64		73

*	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.

166

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Emerging Markets Leaders Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	13.26		$	10.51		$	8.26	$	11.06		$	7.84		$	7.73
Income (loss) from investment operations:
Net investment income (loss)			(0.03	)		(0.02	)		0.03		0.03			0.01			0.02
Net realized and unrealized gain (loss) on investments			0.52			2.88			2.28		(1.97	)		3.26			0.09
Total from investment operations			0.49			2.86			2.31		(1.94	)		3.27			0.11
Less distributions from:
Net investment income			—			—			0.04		0.07			0.05			—
Net realized gain			—			0.11			0.02		0.79			—			—
Total distributions			—			0.11			0.06		0.86			0.05			—
Net asset value, end of year		$	13.75		$	13.26		$	10.51	$	8.26		$	11.06		$	7.84
Total return (%)*			3.70			27.23			27.98		(17.73	)		41.68			1.42
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.58			1.63			1.62		1.60			1.62			1.81
Expenses, net of waivers and reimbursements			1.40			1.40			1.45		1.58			1.47			1.57
Net investment income (loss), before waivers and reimbursements			(0.62	)		(0.45	)		0.17		0.27			(0.01	)		0.05
Net investment income (loss), net of waivers and reimbursements			(0.44	)		(0.22	)		0.34		0.29			0.14			0.29
Class N net assets at the end of the year (in thousands)		$	2,223		$	1,803		$	1,856	$	2,239		$	2,766		$	2,479
Portfolio turnover rate (%)*			29			47			33		52			59			135

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	13.28		$	10.52		$	8.27	$	11.09		$	7.87		$	7.74
Income (loss) from investment operations:
Net investment income (loss)			(0.02	)		(0.00	)^		0.06		0.06			0.02			0.04
Net realized and unrealized gain (loss) on investments			0.53			2.89			2.29		(1.97	)		3.27			0.10
Total from investment operations			0.51			2.89			2.35		(1.91	)		3.29			0.14
Less distributions from:
Net investment income			—			0.02			0.08		0.12			0.07			0.01
Net realized gain			—			0.11			0.02		0.79			—			—
Total distributions			—			0.13			0.10		0.91			0.07			0.01
Net asset value, end of year		$	13.79		$	13.28		$	10.52	$	8.27		$	11.09		$	7.87
Total return (%)*			3.84			27.52			28.36		(17.45	)		41.89			1.82
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.29			1.33			1.29		1.27			1.40			1.54
Expenses, net of waivers and reimbursements			1.15			1.15			1.20		1.27			1.25			1.30
Net investment income (loss), before waivers and reimbursements			(0.38	)		(0.21	)		0.53		0.58			0.09			0.28
Net investment income (loss), net of waivers and reimbursements			(0.24	)		(0.03	)		0.62		0.58			0.24			0.52
Class I net assets at the end of the year (in thousands)		$	55,679		$	62,319		$	45,090	$	34,786		$	47,666		$	30,346
Portfolio turnover rate (%)*			29			47			33		52			59			135

*	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.

June 30, 2021

William Blair Funds

167

Financial Highlights — For a share outstanding throughout each period

Emerging Markets Leaders Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	13.26		$	10.51		$	8.26	$	11.09		$	7.86	$	7.74
Income (loss) from investment operations:
Net investment income (loss)			(0.01	)		0.00	^		0.06		0.07			0.03		0.03
Net realized and unrealized gain (loss) on investments			0.53			2.89			2.29		(1.98	)		3.28		0.10
Total from investment operations			0.52			2.89			2.35		(1.91	)		3.31		0.13
Less distributions from:
Net investment income			—			0.03			0.08		0.13			0.08		0.01
Net realized gain			—			0.11			0.02		0.79			—		—
Total distributions			—			0.14			0.10		0.92			0.08		0.01
Net asset value, end of year		$	13.78		$	13.26		$	10.51	$	8.26		$	11.09	$	7.86
Total return (%)*			3.92			27.50			28.45		(17.46	)		42.15		1.74
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.21			1.26			1.23		1.20			1.19		1.34
Expenses, net of waivers and reimbursements			1.10			1.10			1.15		1.20			1.19		1.25
Net investment income (loss), before waivers and reimbursements			(0.23	)		(0.11	)		0.57		0.71			0.33		0.30
Net investment income (loss), net of waivers and reimbursements			(0.12	)		0.05			0.65		0.71			0.33		0.39
Class R6 net assets at the end of the year (in thousands)		$	258,633		$	198,015		$	191,337	$	161,889		$	427,480	$	272,678
Portfolio turnover rate (%)*			29			47			33		52			59		135

*	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.

168

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Emerging Markets Growth Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	18.42		$	13.67		$	11.14	$	16.20		$	10.99		$	10.85
Income (loss) from investment operations:
Net investment income (loss)			(0.07	)		(0.09	)		0.11		0.01			(0.02	)		0.03
Net realized and unrealized gain (loss) on investments			1.98			5.60			2.98		(3.49	)		5.35			0.13
Total from investment operations			1.91			5.51			3.09		(3.48	)		5.33			0.16
Less distributions from:
Net investment income			—			—			0.16		0.11			0.12			0.02
Net realized gain			—			0.76			0.40		1.47			—			—
Total distributions			—			0.76			0.56		1.58			0.12			0.02
Net asset value, end of year		$	20.33		$	18.42		$	13.67	$	11.14		$	16.20		$	10.99
Total return (%)*			10.37			40.43			27.89		(21.61	)		48.53			1.49
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.52			1.55			1.51		1.52			1.65			1.65
Expenses, net of waivers and reimbursements			1.52			1.55			1.51		1.52			1.50			1.50
Net investment income (loss), before waivers and reimbursements			(0.70	)		(0.60	)		0.84		0.09			(0.29	)		0.13
Net investment income (loss), net of waivers and reimbursements			(0.70	)		(0.60	)		0.84		0.09			(0.14	)		0.28
Class N net assets at the end of the year (in thousands)		$	35,790		$	18,606		$	7,804	$	7,103		$	10,479		$	8,488
Portfolio turnover rate (%)*			31			77			79		113			91			105

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019		2018			2017			2016
Net asset value, beginning of year		$	18.66		$	13.82		$	11.25	$	16.36		$	11.10		$	10.96
Income (loss) from investment operations:
Net investment income (loss)			(0.04	)		(0.05	)		0.14		0.05			0.01			0.06
Net realized and unrealized gain (loss) on investments			2.00			5.66			3.02		(3.52	)		5.40			0.13
Total from investment operations			1.96			5.61			3.16		(3.47	)		5.41			0.19
Less distributions from:
Net investment income			—			0.01			0.19		0.17			0.15			0.05
Net realized gain			—			0.76			0.40		1.47			—			—
Total distributions			—			0.77			0.59		1.64			0.15			0.05
Net asset value, end of year		$	20.62		$	18.66		$	13.82	$	11.25		$	16.36		$	11.10
Total return (%)*			10.50			40.72			28.29		(21.37	)		48.83			1.73
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.23			1.30			1.26		1.27			1.42			1.41
Expenses, net of waivers and reimbursements			1.23			1.30			1.26		1.27			1.27			1.26
Net investment income (loss), before waivers and reimbursements			(0.40	)		(0.33	)		1.06		0.34			(0.07	)		0.38
Net investment income (loss), net of waivers and reimbursements			(0.40	)		(0.33	)		1.06		0.34			0.08			0.53
Class I net assets at the end of the year (in thousands)		$	195,390		$	113,697		$	73,496	$	79,427		$	129,481		$	93,668
Portfolio turnover rate (%)*			31			77			79		113			91			105

*	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.

June 30, 2021

William Blair Funds

169

Financial Highlights — For a share outstanding throughout each period

Emerging Markets Growth Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	18.84		$	13.94		$	11.35	$	16.49		$	11.18	$	11.05
Income (loss) from investment operations:
Net investment income (loss)			(0.03	)		(0.03	)		0.15		0.07			0.02		0.07
Net realized and unrealized gain (loss) on investments			2.02			5.71			3.04		(3.56	)		5.46		0.12
Total from investment operations			1.99			5.68			3.19		(3.49	)		5.48		0.19
Less distributions from:
Net investment income			—			0.02			0.20		0.18			0.17		0.06
Net realized gain			—			0.76			0.40		1.47		��	—		—
Total distributions			—			0.78			0.60		1.65			0.17		0.06
Net asset value, end of year		$	20.83		$	18.84		$	13.94	$	11.35		$	16.49	$	11.18
Total return (%)*			10.56			40.90			28.28		(21.29	)		49.06		1.71
Ratios to average daily net assets (%)**:
Expenses			1.16			1.20			1.19		1.19			1.17		1.19
Net investment income (loss)			(0.35	)		(0.22	)		1.17		0.46			0.17		0.60
Class R6 net assets at the end of the year (in thousands)		$	1,027,330		$	1,063,433		$	708,892	$	654,441		$	1,178,853	$	831,587
Portfolio turnover rate (%)*			31			77			79		113			91		105

*	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.

170

Semiannual Report

June 30, 2021

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,
		2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	22.22		$	16.80		$	13.96		$	18.66		$	13.73		$	14.84
Income (loss) from investment operations:
Net investment income (loss)			(0.10	)		(0.06	)		0.00	^		(0.02	)		0.01			0.09
Net realized and unrealized gain (loss) on investments			3.11			5.48			2.84			(4.38	)		5.46			(0.88	)
Total from investment operations			3.01			5.42			2.84			(4.40	)		5.47			(0.79	)
Less distributions from:
Net investment income			—			—			—			—			0.50			0.32
Net realized gain			—			—			—			0.30			0.04			—
Total distributions			—			—			—			0.30			0.54			0.32
Net asset value, end of year		$	25.23		$	22.22		$	16.80		$	13.96		$	18.66		$	13.73
Total return (%)*			13.55			32.26			20.34			(23.57	)		40.09			(5.33	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.61			1.77			1.71			1.70			1.83			1.82
Expenses, net of waivers and reimbursements			1.55			1.55			1.55			1.58			1.64			1.61
Net investment income (loss), before waivers and reimbursements			(0.95	)		(0.58	)		(0.14	)		(0.22	)		(0.11	)		0.41
Net investment income (loss), net of waivers and reimbursements			(0.89	)		(0.36	)		0.02			(0.10	)		0.08			0.62
Class N net assets at the end of the year (in thousands)		$	4,254		$	3,947		$	4,025		$	8,977		$	15,082		$	9,263
Portfolio turnover rate (%)*			44			119			142			187			183			157

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020			2019			2018			2017			2016
Net asset value, beginning of year		$	22.40		$	16.90		$	14.03		$	18.73		$	13.77		$	14.90
Income (loss) from investment operations:
Net investment income (loss)			(0.07	)		(0.02	)		0.04			0.03			0.08			0.13
Net realized and unrealized gain (loss) on investments			3.14			5.53			2.86			(4.41	)		5.47			(0.89	)
Total from investment operations			3.07			5.51			2.90			(4.38	)		5.55			(0.76	)
Less distributions from:
Net investment income			—			0.01			0.03			0.02			0.55			0.37
Net realized gain			—			—			—			0.30			0.04			—
Total distributions			—			0.01			0.03			0.32			0.59			0.37
Net asset value, end of year		$	25.47		$	22.40		$	16.90		$	14.03		$	18.73		$	13.77
Total return (%)*			13.71			32.60			20.58			(23.31	)		40.53			(5.11	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.31			1.45			1.40			1.38			1.50			1.51
Expenses, net of waivers and reimbursements			1.30			1.30			1.30			1.33			1.31			1.30
Net investment income (loss), before waivers and reimbursements			(0.65	)		(0.25	)		0.18			0.13			0.30			0.66
Net investment income (loss), net of waivers and reimbursements			(0.64	)		(0.10	)		0.28			0.18			0.49			0.87
Class I net assets at the end of the year (in thousands)		$	166,794		$	151,302		$	142,885		$	169,770		$	282,620		$	147,949
Portfolio turnover rate (%)*			44			119			142			187			183			157

*	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.

June 30, 2021

William Blair Funds

171

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,
		2021			2020			2019		2018			2017		2016
Net asset value, beginning of year		$	22.44		$	16.93		$	14.06	$	18.76		$	13.79	$	14.92
Income (loss) from investment operations:
Net investment income (loss)			(0.07	)		(0.00	)^		0.05		0.05			0.10		0.14
Net realized and unrealized gain (loss) on investments			3.15			5.53			2.86		(4.41	)		5.47		(0.89	)
Total from investment operations			3.08			5.53			2.91		(4.36	)		5.57		(0.75	)
Less distributions from:
Net investment income			—			0.02			0.04		0.04			0.56		0.38
Net realized gain			—			—			—		0.30			0.04		—
Total distributions			—			0.02			0.04		0.34			0.60		0.38
Net asset value, end of year		$	25.52		$	22.44		$	16.93	$	14.06		$	18.76	$	13.79
Total return (%)*			13.73			32.66			20.69		(23.24	)		40.62		(5.05	)
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.24			1.36			1.33		1.30			1.29		1.31
Expenses, net of waivers and reimbursements			1.24			1.25			1.25		1.25			1.25		1.25
Net investment income (loss), before waivers and reimbursements			(0.55	)		(0.14	)		0.27		0.22			0.53		0.88
Net investment income (loss), net of waivers and reimbursements			(0.55	)		(0.03	)		0.35		0.27			0.57		0.94
Class R6 net assets at the end of the year (in thousands)		$	319,806		$	152,160		$	130,711	$	98,188		$	166,927	$	125,650
Portfolio turnover rate (%)*			44			119			142		187			183		157

*	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.

172

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Bond Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020		2019		2018			2017		2016
Net asset value, beginning of year		$	10.83		$	10.41	$	9.75	$	10.41		$	10.41	$	10.34
Income (loss) from investment operations:
Net investment income (loss)			0.10			0.24		0.30		0.31			0.27		0.27
Net realized and unrealized gain (loss) on investments			(0.24	)		0.54		0.77		(0.56	)		0.12		0.18
Total from investment operations			(0.14	)		0.78		1.07		(0.25	)		0.39		0.45
Less distributions from:
Net investment income			0.14			0.36		0.41		0.41			0.39		0.38
Net realized gain			—			—		—		—			—		—
Total distributions			0.14			0.36		0.41		0.41			0.39		0.38
Net asset value, end of year		$	10.55		$	10.83	$	10.41	$	9.75		$	10.41	$	10.41
Total return (%)*			(1.23	)		7.63		11.09		(2.42	)		3.83		4.40
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.70			0.79		0.69		0.69			0.82		0.82
Expenses, net of waivers and reimbursements			0.60			0.60		0.60		0.62			0.65		0.65
Net investment income (loss), before waivers and reimbursements			1.72			2.04		2.90		3.01			2.40		2.43
Net investment income (loss), net of waivers and reimbursements			1.82			2.23		2.99		3.08			2.57		2.60
Class N net assets at the end of the year (in thousands)		$	39,108		$	39,522	$	32,176	$	70,253		$	83,662	$	125,866
Portfolio turnover rate (%)*			21			71		58		40			17		17

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020		2019		2018			2017		2016
Net asset value, beginning of year		$	10.71		$	10.30	$	9.65	$	10.31		$	10.30	$	10.24
Income (loss) from investment operations:
Net investment income (loss)			0.10			0.25		0.31		0.32			0.29		0.30
Net realized and unrealized gain (loss) on investments			(0.22	)		0.54		0.76		(0.56	)		0.13		0.16
Total from investment operations			(0.12	)		0.79		1.07		(0.24	)		0.42		0.46
Less distributions from:
Net investment income			0.15			0.38		0.42		0.42			0.41		0.40
Net realized gain			—			—		—		—			—		—
Total distributions			0.15			0.38		0.42		0.42			0.41		0.40
Net asset value, end of year		$	10.44		$	10.71	$	10.30	$	9.65		$	10.31	$	10.30
Total return (%)*			(1.09	)		7.73		11.22		(2.31	)		4.16		4.55
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.49			0.55		0.47		0.46			0.60		0.58
Expenses, net of waivers and reimbursements			0.45			0.45		0.45		0.46			0.43		0.41
Net investment income (loss), before waivers and reimbursements			1.93			2.29		3.10		3.24			2.62		2.66
Net investment income (loss), net of waivers and reimbursements			1.97			2.39		3.12		3.24			2.79		2.83
Class I net assets at the end of the year (in thousands)		$	246,624		$	232,716	$	206,304	$	281,442		$	384,464	$	322,174
Portfolio turnover rate (%)*			21			71		58		40			17		17

*	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.

June 30, 2021

William Blair Funds

173

Financial Highlights — For a share outstanding throughout each period

Bond Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020		2019		2018			2017		2016
Net asset value, beginning of year		$	10.71		$	10.30	$	9.64	$	10.30		$	10.29	$	10.23
Income (loss) from investment operations:
Net investment income (loss)			0.10			0.26		0.32		0.33			0.30		0.30
Net realized and unrealized gain (loss) on investments			(0.23	)		0.53		0.76		(0.56	)		0.13		0.17
Total from investment operations			(0.13	)		0.79		1.08		(0.23	)		0.43		0.47
Less distributions from:
Net investment income			0.15			0.38		0.42		0.43			0.42		0.41
Net realized gain			—			—		—		—			—		—
Total distributions			0.15			0.38		0.42		0.43			0.42		0.41
Net asset value, end of year		$	10.43		$	10.71	$	10.30	$	9.64		$	10.30	$	10.29
Total return (%)*			(1.16	)		7.79		11.39		(2.26	)		4.24		4.61
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.42			0.46		0.41		0.38			0.37		0.37
Expenses, net of waivers and reimbursements			0.40			0.40		0.40		0.38			0.35		0.35
Net investment income (loss), before waivers and reimbursements			2.00			2.39		3.17		3.32			2.85		2.88
Net investment income (loss), net of waivers and reimbursements			2.02			2.45		3.18		3.32			2.87		2.90
Class R6 net assets at the end of the year (in thousands)		$	49,699		$	48,482	$	43,655	$	70,851		$	91,629	$	95,216
Portfolio turnover rate (%)*			21			71		58		40			17		17

*	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.

174

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Income Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020		2019		2018			2017			2016
Net asset value, beginning of year		$	8.71		$	8.57	$	8.36	$	8.72		$	8.86		$	8.90
Income (loss) from investment operations:
Net investment income (loss)			0.04			0.12		0.17		0.17			0.16			0.16
Net realized and unrealized gain (loss) on investments			(0.11	)		0.25		0.32		(0.25	)		(0.03	)		0.06
Total from investment operations			(0.07	)		0.37		0.49		(0.08	)		0.13			0.22
Less distributions from:
Net investment income			0.08			0.23		0.28		0.28			0.27			0.26
Net realized gain			—			—		—		—			—			—
Total distributions			0.08			0.23		0.28		0.28			0.27			0.26
Net asset value, end of year		$	8.56		$	8.71	$	8.57	$	8.36		$	8.72		$	8.86
Total return (%)*			(0.83	)		4.34		5.92		(0.86	)		1.46			2.44
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.92			1.03		0.98		0.91			0.88			0.79
Expenses, net of waivers and reimbursements			0.85			0.85		0.85		0.85			0.85			0.79
Net investment income (loss), before waivers and reimbursements			0.77			1.16		1.85		1.96			1.77			1.80
Net investment income (loss), net of waivers and reimbursements			0.84			1.34		1.98		2.02			1.80			1.80
Class N net assets at the end of the year (in thousands)		$	17,205		$	22,610	$	19,662	$	22,422		$	39,625		$	52,710
Portfolio turnover rate (%)*			33			57		114		97			37			22

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020		2019		2018			2017			2016
Net asset value, beginning of year		$	8.65		$	8.52	$	8.30	$	8.66		$	8.80		$	8.83
Income (loss) from investment operations:
Net investment income (loss)			0.04			0.12		0.18		0.19			0.18			0.18
Net realized and unrealized gain (loss) on investments			(0.11	)		0.25		0.33		(0.25	)		(0.03	)		0.06
Total from investment operations			(0.07	)		0.37		0.51		(0.06	)		0.15			0.24
Less distributions from:
Net investment income			0.08			0.24		0.29		0.30			0.29			0.27
Net realized gain			—			—		—		—			—			—
Total distributions			0.08			0.24		0.29		0.30			0.29			0.27
Net asset value, end of year		$	8.50		$	8.65	$	8.52	$	8.30		$	8.66		$	8.80
Total return (%)*			(0.76	)		4.39		6.24		(0.69	)		1.68			2.78
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.68			0.78		0.74		0.65			0.62			0.57
Expenses, net of waivers and reimbursements			0.68			0.70		0.70		0.65			0.62			0.57
Net investment income (loss), before waivers and reimbursements			1.01			1.35		2.10		2.22			2.03			2.05
Net investment income (loss), net of waivers and reimbursements			1.01			1.43		2.14		2.22			2.03			2.05
Class I net assets at the end of the year (in thousands)		$	34,654		$	45,641	$	31,629	$	34,793		$	51,153		$	58,160
Portfolio turnover rate (%)*			33			57		114		97			37			22

*	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.

June 30, 2021

William Blair Funds

175

Financial Highlights — For a share outstanding throughout each period

Income Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020			2019(a)
Net asset value, beginning of year		$	8.65			$	8.52		$	8.45
Income (loss) from investment operations:
Net investment income (loss)			0.04				0.13			0.09
Net realized and unrealized gain (loss) on investments			(0.10	)			0.24			0.18
Total from investment operations			(0.06	)			0.37			0.27
Less distributions from:
Net investment income			0.09				0.24			0.20
Net realized gain			—				—			—
Total distributions			0.09				0.24			0.20
Net asset value, end of year		$	8.50			$	8.65		$	8.52
Total return (%)*			(0.73	)			4.44			3.18
Ratios to average daily net assets (%)**:
Expenses, before of waivers and reimbursements			0.62				0.73			0.71
Expenses, net waivers and reimbursements			0.62				0.65			0.65
Net investment income (loss), before of waivers and reimbursements			1.00				1.47			1.46
Net investment income (loss), net waivers and reimbursements			1.00				1.55			1.52
Class R6 net assets at end of year (in thousands)		$	190			$	71		$	52
Portfolio turnover rate (%)*			33				57			114

(a)	For the period from May 2, 2019 (Commencement of Operations) to December 31, 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.

176

Semiannual Report

June 30, 2021

Financial Highlights — For a share outstanding throughout each period

Low Duration Fund

	Class N
	(unaudited) Period Ended June 30,				Years Ended December 31,
		2021			2020		2019		2018			2017			2016
Net asset value, beginning of year		$	8.65		$	8.68	$	8.70	$	8.92		$	9.07		$	9.16
Income (loss) from investment operations:
Net investment income (loss)			0.02			0.08		0.19		0.17			0.11			0.09
Net realized and unrealized gain (loss) on investments			(0.02	)		0.14		0.11		(0.10	)		(0.04	)		0.02
Total from investment operations			—			0.22		0.30		0.07			0.07			0.11
Less distributions from:
Net investment income			0.08			0.25		0.32		0.29			0.22			0.20
Net realized gain			—			—		—		—			—			—
Total distributions			0.08			0.25		0.32		0.29			0.22			0.20
Net asset value, end of year		$	8.57		$	8.65	$	8.68	$	8.70		$	8.92		$	9.07
Total return (%)*			0.05			2.56		3.48		0.80			0.84			1.16
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.71			0.84		0.75		0.72			0.79			0.83
Expenses, net of waivers and reimbursements			0.55			0.55		0.55		0.58			0.61			0.68
Net investment income (loss), before waivers and reimbursements			0.28			0.60		1.96		1.83			1.04			0.83
Net investment income (loss), net of waivers and reimbursements			0.44			0.89		2.16		1.97			1.22			0.98
Class N net assets at the end of the year (in thousands)		$	16,119		$	13,736	$	1,513	$	1,661		$	1,979		$	7,237
Portfolio turnover rate (%)*			82			72		183		122			109			81

	Class I
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020		2019		2018			2017			2016
Net asset value, beginning of year		$	8.64		$	8.67	$	8.70	$	8.91		$	9.07		$	9.16
Income (loss) from investment operations:
Net investment income (loss)			0.03			0.10		0.20		0.19			0.13			0.11
Net realized and unrealized gain (loss) on investments			(0.02	)		0.13		0.10		(0.09	)		(0.05	)		0.02
Total from investment operations			0.01			0.23		0.30		0.10			0.08			0.13
Less distributions from:
Net investment income			0.09			0.26		0.33		0.31			0.24			0.22
Net realized gain			—			—		—		—			—			—
Total distributions			0.09			0.26		0.33		0.31			0.24			0.22
Net asset value, end of year		$	8.56		$	8.64	$	8.67	$	8.70		$	8.91		$	9.07
Total return (%)*			0.12			2.72		3.52		1.12			0.91			1.40
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.51			0.60		0.53		0.46			0.59			0.59
Expenses, net of waivers and reimbursements			0.40			0.40		0.40		0.39			0.41			0.44
Net investment income (loss), before waivers and reimbursements			0.49			0.98		2.19		2.05			1.27			1.05
Net investment income (loss), net of waivers and reimbursements			0.60			1.18		2.32		2.12			1.45			1.20
Class I net assets at the end of the year (in thousands)		$	102,003		$	104,093	$	38,156	$	56,120		$	131,186		$	219,714
Portfolio turnover rate (%)*			82			72		183		122			109			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.

June 30, 2021

William Blair Funds

177

Financial Highlights — For a share outstanding throughout each period

Low Duration Fund

	Class R6
	(unaudited) Period Ended June 30,				Years Ended December 31,
			2021			2020		2019		2018			2017			2016
Net asset value, beginning of year		$	8.64		$	8.68	$	8.70	$	8.91		$	9.07		$	9.16
Income (loss) from investment operations:
Net investment income (loss)			0.03			0.12		0.21		0.19			0.14			0.11
Net realized and unrealized gain (loss) on investments			(0.02	)		0.11		0.11		(0.09	)		(0.05	)		0.02
Total from investment operations			0.01			0.23		0.32		0.10			0.09			0.13
Less distributions from:
Net investment income			0.09			0.27		0.34		0.31			0.25			0.22
Net realized gain			—			—		—		—			—			—
Total distributions			0.09			0.27		0.34		0.31			0.25			0.22
Net asset value, end of year		$	8.56		$	8.64	$	8.68	$	8.70		$	8.91		$	9.07
Total return (%)*			0.15			2.65		3.69		1.15			0.96			1.43
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.47			0.53		0.50		0.42			0.40			0.40
Expenses, net of waivers and reimbursements			0.35			0.35		0.35		0.35			0.37			0.40
Net investment income (loss), before waivers and reimbursements			0.53			1.19		2.22		2.10			1.48			1.25
Net investment income (loss), net of waivers and reimbursements			0.65			1.37		2.37		2.17			1.51			1.25
Class R6 net assets at the end of the year (in thousands)		$	22,571		$	40,551	$	36,846	$	47,585		$	99,912		$	53,122
Portfolio turnover rate (%)*			82			72		183		122			109			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.

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Financial Highlights — For a share outstanding throughout each period

Emerging Markets Debt Fund

	Class I
	(unaudited) Period Ended June 30,
		2021(a)
Net asset value, beginning of year		$	10.00
Income (loss) from investment operations:
Net investment income (loss)			0.04
Net realized and unrealized gain (loss) on investments			(0.00	)^
Total from investment operations			0.04
Less distributions from:
Net investment income			0.04
Net realized gain			—
Total distributions			0.04
Net asset value, end of year		$	10.00
Total return (%)*			0.37
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.51
Expenses, net of waivers and reimbursements			0.70
Net investment income (loss), before waivers and reimbursements			3.22
Net investment income (loss), net of waivers and reimbursements			4.03
Class I net assets at end of year (in thousands)		$	1,151
Portfolio turnover rate (%)*			17

	Class R6
	(unaudited) Period Ended June 30,
			2021(a)
Net asset value, beginning of year		$	10.00
Income (loss) from investment operations:
Net investment income (loss)			0.04
Net realized and unrealized gain (loss) on investments			(0.00	)^
Total from investment operations			0.04
Less distributions from:
Net investment income			0.04
Net realized gain			—
Total distributions			0.04
Net asset value, end of year		$	10.00
Total return (%)*			0.37
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.53
Expenses, net of waivers and reimbursements			0.65
Net investment income (loss), before waivers and reimbursements			3.23
Net investment income (loss), net of waivers and reimbursements			4.11
Class R6 net assets at end of year (in thousands)		$	22,874
Portfolio turnover rate (%)*			17

(a)	For the period from May 25, 2021 (Commencement of Operations) to June 30, 2021.
*	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.

June 30, 2021

William Blair Funds

179

Financial Highlights — For a share outstanding throughout each period

Macro Allocation Fund

	Class N
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2021		2020			2019		2018			2017		2016
Net asset value, beginning of year		$	10.93	$	11.44		$	11.41	$	11.84		$	11.34	$	11.32
Income (loss) from investment operations:
Net investment income (loss)			0.02		0.04			0.08		0.08			0.06		0.04
Net realized and unrealized gain (loss) on investments			0.40		(0.44	)		0.37		(0.24	)		0.51		0.19
Total from investment operations			0.42		(0.40	)		0.45		(0.16	)		0.57		0.23
Less distributions from:
Net investment income			—		0.11			0.42		0.27			0.07		0.21
Net realized gain			—		—			—		—			—		—
Total distributions			—		0.11			0.42		0.27			0.07		0.21
Net asset value, end of year		$	11.35	$	10.93		$	11.44	$	11.41		$	11.84	$	11.34
Total return (%)*			3.84		(3.49	)		3.97		(1.30	)		5.06		2.01
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.37		1.36			1.22		1.30			1.52		1.38
Expenses, net of waivers and reimbursements			1.25		1.26			1.22		1.30			1.37		1.23
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			1.23		1.25			1.21		1.28			1.31		1.23
Net investment income (loss), before waivers and reimbursements			0.24		0.26			0.70		0.66			0.35		0.17
Net investment income (loss), net of waivers and reimbursements			0.36		0.36			0.70		0.66			0.50		0.32
Class N net assets at the end of the year (in thousands)		$	7,124	$	7,674		$	13,717	$	43,463		$	41,483	$	61,376
Portfolio turnover rate (%)*			25		29			31		36			43		50

	Class I
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2021		2020			2019		2018			2017		2016
Net asset value, beginning of year		$	10.85	$	11.35		$	11.38	$	11.88		$	11.38	$	11.38
Income (loss) from investment operations:
Net investment income (loss)			0.03		0.06			0.13		0.11			0.11		0.08
Net realized and unrealized gain (loss) on investments			0.40		(0.42	)		0.34		(0.24	)		0.51		0.18
Total from investment operations			0.43		(0.36	)		0.47		(0.13	)		0.62		0.26
Less distributions from:
Net investment income			—		0.14			0.50		0.37			0.12		0.26
Net realized gain			—		—			—		—			—		—
Total distributions			—		0.14			0.50		0.37			0.12		0.26
Net asset value, end of year		$	11.28	$	10.85		$	11.35	$	11.38		$	11.88	$	11.38
Total return (%)*			3.96		(3.15	)		4.14		(1.08	)		5.50		2.26
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			1.10		1.04			0.97		0.99			1.17		1.12
Expenses, net of waivers and reimbursements			1.00		1.01			0.97		0.99			1.02		0.97
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			0.98		1.00			0.96		0.97			0.96		0.97
Net investment income (loss), before waivers and reimbursements			0.39		0.56			1.09		0.95			0.75		0.52
Net investment income (loss), net of waivers and reimbursements			0.49		0.59			1.09		0.95			0.90		0.67
Class I net assets at the end of the year (in thousands)		$	95,007	$	171,153		$	358,935	$	486,543		$	780,075	$	937,244
Portfolio turnover rate (%)*			25		29			31		36			43		50

*	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.

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Financial Highlights — For a share outstanding throughout each period

Macro Allocation Fund

	Class R6
	(unaudited) Period Ended June 30,			Years Ended December 31,
			2021		2020			2019		2018			2017		2016
Net asset value, beginning of year		$	10.85	$	11.36		$	11.38	$	11.89		$	11.40	$	11.39
Income (loss) from investment operations:
Net investment income (loss)			0.04		0.08			0.14		0.13			0.12		0.09
Net realized and unrealized gain (loss) on investments			0.40		(0.44	)		0.34		(0.24	)		0.51		0.19
Total from investment operations			0.44		(0.36	)		0.48		(0.11	)		0.63		0.28
Less distributions from:
Net investment income			—		0.15			0.50		0.40			0.14		0.27
Net realized gain			—		—			—		—			—		—
Total distributions			—		0.15			0.50		0.40			0.14		0.27
Net asset value, end of year		$	11.29	$	10.85		$	11.36	$	11.38		$	11.89	$	11.40
Total return (%)*			4.06		(3.13	)		4.29		(0.94	)		5.51		2.44
Ratios to average daily net assets (%)**:
Expenses, before waivers and reimbursements			0.98		0.93			0.89		0.91			0.92		0.89
Expenses, net of waivers and reimbursements			0.95		0.93			0.89		0.91			0.92		0.89
Expenses (excluding interest or short dividend expense), net of waivers and reimbursements			0.94		0.92			0.88		0.89			0.86		0.89
Net investment income (loss), before waivers and reimbursements			0.68		0.70			1.23		1.10			1.04		0.81
Net investment income (loss), net of waivers and reimbursements			0.71		0.70			1.23		1.10			1.04		0.81
Class R6 net assets at the end of the year (in thousands)		$	118,310	$	174,888		$	378,148	$	391,812		$	487,082	$	582,298
Portfolio turnover rate (%)*			25		29			31		36			43		50

*	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.

June 30, 2021

William Blair Funds

181

Renewal of the Management Agreement

On April 28, 2021, 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 (the “Adviser”) on behalf of each of the William Blair Funds (each, a “Fund” and collectively, the “Funds”), with the exception of the Emerging Markets Debt Fund, for which the Management Agreement was approved for an initial two-year term by the Board on April 29, 2020, and the China Growth Fund, for which the Management Agreement was approved for an initial two-year term by the Board on April 28, 2021. 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 necessary to evaluate the terms of the Management Agreement. 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 28, 2021 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 Independent Trustees also received a memorandum from legal counsel advising them 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 the 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 a 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

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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 Adviser pays the compensation of all of the officers 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, 2020, 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 I shares were used for comparison purposes as the Board noted that Class I shares represent the largest percentage of assets in the Trust. In evaluating performance, the Board recognized that the performance data reflects a snapshot of a period as of a particular date and that selecting a different performance period could produce different results.

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 the Adviser had managed the Funds consistent with their respective investment strategies. 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 below the average of its Morningstar performance peer universe for the one-year period and above the average of its Morningstar performance peer universe for the three- and five-year periods ended December 31, 2020.The Board also considered that the Fund underperformed the benchmark (Russell 3000^®Growth Index) for the one- and five-year periods and outperformed the benchmark for the three-year period ended December 31, 2020.

Large 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 (Russell 1000^®Growth Index) for the one-year period and above the average of its Morningstar performance peer universe and the benchmark for the three- and five-year periods ended December 31, 2020.

Mid 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 (Russell Midcap^®Growth Index) for the one-, three- and five-year periods ended December 31, 2020.The Board considered the Adviser’s view that the Fund’s relative underperformance for the three- and five-year periods was the result of stock specific issues and style headwinds.

Small-Mid Cap Core 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™ Total Return Index) for the one-year period ended December 31, 2020.The Board also considered that the Fund commenced operations on October 1, 2019.

Small-Mid 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, 2020.The Board also considered that the Fund underperformed the benchmark (Russell 2500™ Growth Index) for the one-, three- and five-year periods ended December 31, 2020.

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, 2020.The Board also considered that the Fund outperformed the benchmark (Russell 2000^®Growth Index) for the one-, three- and five-year periods ended December 31, 2020.

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, 2020.The Board also considered the proposed reorganization of the ICM Small Company Portfolio with the Fund.

Global 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 IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2020.

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, 2020.

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William Blair Funds

183

International Growth 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, 2020.

Institutional International Growth 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, 2020.

International Small 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- and three-year periods and below the average of its Morningstar performance peer universe for the five-year period ended December 31, 2020.The Board also considered that the Fund outperformed the benchmark (MSCI All Country World Ex-U.S. Small Cap (net) Index) for the one-, three- and five-year periods ended December 31, 2020.

Emerging Markets 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 Emerging Markets (net) Index) for the one-, three- and five-year periods ended December 31, 2020.

Emerging Markets Growth Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (MSCI Emerging Markets IMI (net) Index) for the one-, three- and five-year periods ended December 31, 2020.

Emerging Markets Small 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- and three-year periods and below the average of its Morningstar performance peer universe for the five-year period ended December 31, 2020.The Board also considered that the Fund outperformed the benchmark (MSCI Emerging Markets Small Cap (net) Index) for the one-, three- and five-year periods ended December 31, 2020.

Bond Fund. The Board considered that the Fund’s total return was below the average of its Morningstar performance peer universe for the one-year period and above the average of its Morningstar performance peer universe for the three- and five-year periods ended December 31, 2020.The Board also considered that the Fund outperformed the benchmark (Bloomberg Barclays U.S. Aggregate Bond Index) for the one-, three- and five-year periods ended December 31, 2020.

Income 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, 2020.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, 2020.

Low Duration Fund. The Board considered that the Fund’s total return was above the average of its Morningstar performance peer universe and the benchmark (ICE BofAML 1-Year US Treasury Note Index) for the one-, three- and five-year periods ended December 31, 2020.

Macro Allocation 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, 2020.The Board also considered that the Fund underperformed the benchmark (ICE BofAML 3-Month US Treasury Bill Index) for the one- and three-year periods and outperformed the benchmark for the five-year period ended December 31, 2020.The Board considered that the portfolio managers’ process was based on fundamental valuation, which had faced headwinds from market forces in recent years, including from the low to negative interest rate environment, and also considered the Advisers’ view that as the investment environment evolves back to one in which fundamentals exert a more consistent influence on prices, prices are expected to gravitate to fundamental valuations.

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 (the “Class I Broadridge Expense Group”) and Class R6 of each Fund 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, the Board noted that the contractual management fees for the Growth Fund, the Large Cap Growth Fund, the Small Cap Value Fund,

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the International Small Cap Growth Fund, the Emerging Markets Small Cap Growth Fund, the Bond Fund, the Income Fund, the Low Duration Fund and the Macro Allocation Fund were below the average contractual management fees of their respective Class I Broadridge Expense Groups. The Board also noted that the contractual management fees for the Mid Cap Growth Fund, the Small-Mid Cap Core Fund, the Small-Mid Cap Growth Fund, the Small Cap Growth Fund, the Global Leaders Fund, the International Leaders Fund, the International Growth Fund, the Emerging Markets Leaders Fund and the Emerging Markets Growth Fund were above the average contractual management fees of their respective Class I Broadridge Expense Groups. The Board also considered that the Adviser had reduced the contractual management fee for the Small Cap Value Fund effective March 1, 2021.

In considering the management fee for the Institutional International Growth Fund, which does not have share classes, the Board noted that the contractual management fee for the Fund was above the average contractual management fee of its Broadridge expense peer group.

The Board noted the current and proposed contractual expense limitations for the Funds and further noted that the Adviser had reduced the contractual limit on operating expenses for the Small Cap Value Fund effective March 1, 2021. The Board considered that the Adviser proposed to contractually limit operating expenses until April 30, 2022 for each share class of the Funds. The Board considered the amount of management fees waived and other expenses reimbursed by the Adviser on behalf of the Funds in 2020.

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 and Emerging Markets Small Cap Growth Fund are closed to investors, except as noted in each Fund’s prospectus.

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.

June 30, 2021

William Blair Funds

185

Approval of the Management Agreement for the William Blair Emerging Markets Debt Fund

On April 29, 2020, the Board of Trustees (the “Board”) of 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 Management Agreement between the Trust, on behalf of the William Blair Emerging Markets Debt Fund (the “Fund”), and William Blair Investment Management, LLC (the “Adviser”).The Independent Trustees met independently of Trust management and the interested Trustees of the Trust to consider the approval of the Management Agreement. The Independent Trustees reviewed materials provided by the Adviser and Broadridge for the approval of the Management Agreement and were assisted by independent legal counsel in making their determination. The Board determined that, given the totality of the information provided with respect to the Management Agreement, the Board had received sufficient information to consider the approval of the Management Agreement. The Board considered the following factors in making its determination, but did not identify any single factor or group of factors as all important or controlling and considered all factors together.

Nature, Quality and Extent of Services. In evaluating the nature, quality and extent of the services expected to be provided by the Adviser to the Fund, the Board noted that the Adviser is a quality firm with a reputation for integrity and honesty that employs high quality people. The Board considered biographical information about the Fund’s portfolio managers and financial information regarding the Adviser. The Board considered the proposed portfolio management team members’ previous experience investing in emerging markets debt. The Board also considered the Adviser’s experience in managing new funds. Based upon all relevant factors, the Board concluded that the nature, quality and extent of the services to be provided by the Adviser to the Fund were expected to be satisfactory.

Fees and Expenses. The Board reviewed the proposed advisory fee for the Fund and reviewed information comparing the advisory fee to a peer group and a peer universe of institutional funds provided by Broadridge. The Broadridge peer group consisted of the Fund and eleven other no-load institutional emerging markets hard currency debt funds with no Rule 12b-1 fees, as classified by Broadridge. The Broadridge peer universe consisted of the Fund, the Fund’s Broadridge peer group and all other institutional emerging markets hard currency debt funds, excluding outliers. In considering the information, the Board noted that the proposed advisory fee for the Fund was below the average contractual management fee of the peer group. The Board also considered that the Adviser had proposed to limit total operating expenses, including waiving advisory fees for each share class of the Fund until April 30, 2022.On the basis of the information provided, the Board concluded that the proposed advisory fee was reasonable in light of the nature, quality and extent of services expected to be provided by the Adviser.

Profitability. With respect to the estimated profitability of the Management Agreement to the Adviser, the Board considered the proposed advisory fee, that the Fund was newly organized, the amount of assets under management that the Adviser initially expected in the Fund and the Adviser’s agreement to limit total expenses until April 30, 2022.The Board considered that the Adviser will be incurring all expenses related to the organization of the Fund. The Board concluded that the expected profits to be realized by the Adviser were not expected to be unreasonable.

Economies of Scale. The Board considered the extent to which economies of scale would be realized as the Fund grows and whether fee levels reflect these economies of scale for the benefit of investors. In considering whether fee levels reflect economies of scale for the benefit of Fund investors, the Board reviewed the Fund’s advisory fee compared to peer funds and the Fund’s estimated expense ratios giving effect to the Adviser’s agreement to limit total expenses until April 30, 2022, and concluded that the advisory fee was reasonable. 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 the asset capacity of the Fund’s investment strategy was constrained by the Adviser and that opportunities for economies of scale would be limited.

Other Benefits to the Adviser. The Board considered benefits to be derived by the Adviser from its relationship with the Fund, including receipt of research from brokerage firms; for Class I shares, reimbursement of some intermediary fees in the nature of sub-transfer agency fees and favorable media coverage. The Board concluded that, after taking into account these benefits, the proposed advisory fee was reasonable.

Conclusion. Based upon all of the information considered and the conclusions reached, the Board determined that the terms of the Management Agreement are fair and reasonable and that the approval of the Management Agreement is in the best interests of the Fund.

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Review of Liquidity Risk Management Program

The Board of Trustees (the “Board”) of William Blair Funds previously approved the William Blair Funds Liquidity Risk Management Program Policy (the “Policy”) under Rule 22e-4 under the 1940 Act (the “Liquidity Rule”), which sets forth the terms of the William Blair Liquidity Risk Management Program (the “Program”). The Program (through the Policy) seeks to assess, manage and review each Fund’s liquidity risk. For purposes of the Program, the Policy and the Liquidity Rule, “liquidity risk” is defined as the risk that a Fund could not meet requests to redeem shares issued by a Fund without significant dilution of remaining investors’ interest in the Funds. Among other things, the Liquidity Rule requires that a written report be provided to the Board on an annual basis that addresses the operation of the Program and assesses the adequacy and effectiveness of its implementation, including (if applicable) the operation of any highly liquid investment minimum (“HLIM”) established for a Fund and any material changes to the Program.

The Board designated the Liquidity Risk Management Committee of William Blair Investment Management, LLC, the Funds’ investment adviser, to be the administrator for the Program (the “Program Administrator”). On February 23, 2021, the Board of Trustees reviewed the Program Administrator’s written report (the “Report”) concerning the operation of the Program and the Policy as well as the adequacy and effectiveness of the Program’s and Policy’s implementation for the period from January 1, 2020 through December 31, 2020 (the “Program Reporting Period”). There were no material changes to the Program or to the Policy during the Program Reporting Period.

The Report summarized the operation of the Program and the Policy and the information and factors considered by the Program Administrator in assessing whether the Program and the Policy have been adequately and effectively implemented with respect to each Fund. Such information and factors included, among other things: (1) the liquidity risk framework used to assess, manage, and periodically review each Fund’s liquidity risk and the results of this assessment; (2) the classification of each of the Funds’ respective investments into one of four liquidity categories that reflect an estimate of their liquidity under normal and reasonably foreseeable stressed conditions; (3) whether a Fund invested primarily in “Highly Liquid Investments” (as defined under the Liquidity Rule) and whether an HLIM should be established for any Fund; (4) whether a Fund invested more than 15% of its assets in “Illiquid Investments” (as defined under the Liquidity Rule); (5) specific liquidity events arising during the Program Reporting Period, including the impact on Fund liquidity caused by extended non-U.S. market closures; and (6) the nature and quality of the services provided by the service provider engaged to assist with determining liquidity classifications for the Funds. Based on this review, the Report concluded that the Program and the Policy meet the requirements of the Liquidity Rule and are operating effectively.

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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 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, CFA, 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 to 2018	Global Head of Investment Management since 2017, portfolio manager (2014 to 2017) and Partner, William Blair	20	Chairman, William Blair SICAV
Arthur J. Simon, 1954⁽²⁾	Trustee	Since 2018	General Counsel and Partner, William Blair	20	Director, William Blair SICAV
Non-Interested Trustees
Vann A. Avedisian, 1964	Trustee	Since 2012	Co-founder and Partner, Newbond Holdings (real estate operations) (since 2021); formerly, Principal, Highgate Holdings (hotel investments) (2009-2021); formerly, co-founder and Managing Director, Oxford Capital Partners Inc. (1994 to 2006)	20	Potbelly Sandwich Works (2001 to 2015 and since 2021)
Kathleen T. Barr, 1955	Trustee	Since 2013	Retired; Chairman of the Governing Council, Independent Directors Council (since 2020); 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)	20	Muzinich BDC, Inc. (since 2019); Board of Governors, Investment Company Institute (since 2019); Professionally Managed Portfolios (since 2018)

†	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’).
*	The number shown does not include three additional series of the Trust that are in existence, but not currently offered to the public.
**	Includes directorships of public companies and other registered investment companies held during the past five years.

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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⁽³⁾	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	20	Donnelley 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 to 2013)⁽⁴⁾	20	Skyway Concession Company, LLC (since 2018); Illinois CPA Society (since 2017); Lifeway Foods, Inc. (since 2020); American Institute of Certified Public Accountants (2013 to 2016); Chicago Finance Exchange (2009 to 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 to 2004)	20	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 to 2010)⁽⁵⁾	20	Engine Media Holdings, Inc. (media group supporting esports, news streaming and gaming) (2020 to 2021); Frankly Inc. (technology products/ services for media industry) (2016 to its 2020 acquisition by Engine Media Holdings); Insignia Systems, Inc. (in-store advertising services for consumer packaged goods manufacturers) (2013 to 2019)

(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 Independent Trustees occurs no later than at the conclusion of the calendar year that occurs after the earlier of (a) the Independent Trustee’s 75th birthday or (b) the 17th anniversary of the date that the Independent 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)	The Trust and William Blair use Donnelley Financial Solutions, Inc. (“DFS’’) for financial printing and other services. DFS is a public company. The Trust and William Blair in the aggregate paid DFS approximately $188,000 and $214,000 in 2019 and 2020, respectively, for the services provided. DFS’s revenue was approximately $900 million in 2019 and $895 million in 2020. Mr. Leib, as the Chief Executive Officer of DFS, is not directly involved in any of the services provided to the Trust or William Blair and his compensation is not materially affected by the fees DFS receives from the Trust and William Blair.
(4)	As a former partner of the audit firm Crowe LLP (formerly, Crowe Horwath LLP), Ms. McWhorter received distributions of her capital in the firm over time and those distributions were completed in March 2021. The Trust and William Blair made no payments to Crowe LLP over the past three years.
(5)	The Trust engages KPMG to provide foreign tax services in Taiwan. KPMG does not provide audit or audit-related services to the Trust. Mr. Zenz is a former partner of KPMG and receives pension/retirement funds from KPMG.

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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

Alaina Anderson, CFA, 1975	Senior Vice President	Since 2021	Partner, William Blair

Marcelo Assalin, CFA, 1973	Senior Vice President	Since 2020	Associate, William Blair (since 2020); formerly, NN Investment Partners (2013- 2020)

Thomas Clarke, 1968	Senior Vice President	Since 2011	Partner, William Blair

Daniel Crowe, CFA, 1972	Senior Vice President	Since 2016	Partner, William Blair

Robert J. Duwa, CFA, 1967	Senior Vice President	Since 2019	Partner, William Blair

Simon Fennell, 1969	Senior Vice President	Since 2013	Partner, William Blair

Andrew G. Flynn, CFA, 1961	Senior Vice President	Since 2013	Partner, William Blair

David C. Fording, CFA, 1967	Senior Vice President	Since 2006	Partner, William Blair

James S. Golan, CFA, 1961	Senior Vice President	Since 2005	Partner, William Blair

William V. Heaphy, CFA, 1967	Senior Vice President	Since 2021	Associate, William Blair (since 2021); formerly, Principal, Investment Counselors of Maryland, LLC (1994-2021)

James E. Jones, CFA, 1977	Senior Vice President	Since 2019	Partner, William Blair

Kenneth J. McAtamney, 1966	Senior Vice President	Since 2008	Partner, William Blair

Todd M. McClone, CFA, 1968	Senior Vice President	Since 2005	Partner, William Blair

John C. Murphy, CFA, 1969	Senior Vice President	Since 2014	Partner, William Blair

D.J. Neiman, CFA, 1975	Senior Vice President	Since 2021	Partner, William Blair

Casey K. Preyss, CFA, 1976	Senior Vice President	Since 2015	Partner, William Blair

David P. Ricci, CFA, 1958	Senior Vice President	Since 2006	Partner, William Blair

Lisa D. Rusch, 1970	Senior Vice President Vice President	Since 2020 2018-2020	Partner, William Blair (since 2020); formerly, Associate, William Blair

Hugo Scott-Gall, 1971	Senior Vice President	Since 2021	Partner, William Blair (since 2018); formerly, Managing Director, Goldman Sachs (1998-2018)

Ward D. Sexton, CFA, 1974	Senior Vice President	Since 2016	Partner, William Blair

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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

Brian D. Singer, CFA, 1960	Senior Vice President	Since 2011	Partner, William Blair

Mark C. Thompson, CFA, 1976	Senior Vice President	Since 2020	Partner, William Blair

Vivian Lin Thurston, CFA, 1972	Senior Vice President	Since 2021	Partner, William Blair

Dan Zelazny, 1971	Senior Vice President	Since 2019	Associate, William Blair (since 2019); formerly, Managing Director, AQR Capital Management (2011-2019)

Ruta Ziverte, 1973	Senior Vice President	Since 2020	Partner, William Blair (since 2021); formerly, Associate, William Blair (2019-2021), Oppenheimer Funds (2015-2019)

Kathleen M. Lynch, CFA, 1971	Vice President	Since 2020	Associate, William Blair

Vesta Marks, CFA, CAIA, 1978	Vice President	Since 2021	Associate, William Blair (since 2021); formerly, Managing Director, Tortoise Capital Advisors (2018-2021), Palmer Square Capital Management LLC (2015-2018)

Gary J. Merwitz, 1970	Vice President	Since 2021	Associate, William Blair (since 2021); formerly, Principal, Investment Counselors of Maryland, LLC (2004-2021)

Marco Ruijer, CFA, 1975	Vice President	Since 2020	Associate, William Blair (since 2020); formerly, NN Investment Partners (2013-2020)

John M. Raczek, 1970	Treasurer Assistant Treasurer	Since 2019 2010-2019	Associate, William Blair

Andrew T. Pfau, 1970	Secretary	Since 2009	Associate, William Blair

David M. Cihak, 1982	Assistant Treasurer	Since 2019	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

(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.

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(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), at www.williamblairfunds.com and on the SEC’s website at http://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 at http://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, 2020 (in thousands):

Fund	Capital Gain Dividend
Growth	$	38,359
Large Cap Growth		32,144
Mid Cap Growth		5,611
Small-Mid Cap Growth		64,284
Small Cap Growth		51,936
Small Cap Value		28,599
Global Leaders		15,321
International Leaders		8,192
International Growth		17,392
Institutional International Growth		183,461
International Small Cap Growth		7,037
Emerging Markets Leaders		2,367
Emerging Markets Growth		48,790

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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, as applicable), 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, 2021 to June 30, 2021.

Actual Expenses

In each example, the first line for each share class in the table provides information about the actual account values and actual expenses. 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 about hypothetical account values and hypothetical expenses 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.

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Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2021		Ending Account Value 6/30/2021		Expenses Paid During the Period (a)		Annualized Expense Ratio
Growth Fund
Class N-actual return	$	1,000.00	$	1,130.94	$	6.34		1.20	%
Class N-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Class I-actual return	$	1,000.00	$	1,132.70	$	4.71		0.89
Class I-hypothetical 5% return	$	1,000.00	$	1,045.59	$	4.51		0.89
Class R6-actual return	$	1,000.00	$	1,133.14	$	4.44		0.84
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.83	$	4.26		0.84
Large Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,141.79	$	4.78		0.90
Class N-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
Class I-actual return	$	1,000.00	$	1,143.26	$	3.45		0.65
Class I-hypothetical 5% return	$	1,000.00	$	1,046.78	$	3.30		0.65
Class R6-actual return	$	1,000.00	$	1,143.39	$	3.19		0.60
Class R6-hypothetical 5% return	$	1,000.00	$	1,047.02	$	3.05		0.60
Mid Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,035.69	$	6.06		1.20
Class N-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Class I-actual return	$	1,000.00	$	1,036.09	$	4.80		0.95
Class I-hypothetical 5% return	$	1,000.00	$	1,045.29	$	4.82		0.95
Class R6-actual return	$	1,000.00	$	1,036.78	$	4.55		0.90
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
Small-Mid Cap Core Fund
Class I-actual return	$	1,000.00	$	1,183.23	$	5.14		0.95
Class I-hypothetical 5% return	$	1,000.00	$	1,045.29	$	4.82		0.95
Class R6-actual return	$	1,000.00	$	1,184.01	$	4.87		0.90
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
Small-Mid Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,080.40	$	6.96		1.35
Class N-hypothetical 5% return	$	1,000.00	$	1,043.31	$	6.84		1.35
Class I-actual return	$	1,000.00	$	1,081.70	$	5.68		1.10
Class I-hypothetical 5% return	$	1,000.00	$	1,044.55	$	5.58		1.10
Class R6-actual return	$	1,000.00	$	1,081.86	$	5.32		1.03
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.89	$	5.22		1.03
Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,128.44	$	7.92		1.50
Class N-hypothetical 5% return	$	1,000.00	$	1,042.56	$	7.60		1.50
Class I-actual return	$	1,000.00	$	1,130.08	$	6.60		1.25
Class I-hypothetical 5% return	$	1,000.00	$	1,043.80	$	6.33		1.25
Class R6-actual return	$	1,000.00	$	1,130.46	$	6.13		1.16
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.25	$	5.88		1.16
Small Cap Value Fund
Class N-actual return	$	1,000.00	$	1,176.38	$	6.21		1.15
Class N-hypothetical 5% return	$	1,000.00	$	1,044.30	$	5.83		1.15
Class I-actual return	$	1,000.00	$	1,178.33	$	4.81		0.89
Class I-hypothetical 5% return	$	1,000.00	$	1,045.59	$	4.51		0.89
Class R6-actual return	$	1,000.00	$	1,178.47	$	4.59		0.85
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.78	$	4.31		0.85
Global Leaders Fund
Class N-actual return	$	1,000.00	$	1,107.98	$	6.01		1.15
Class N-hypothetical 5% return	$	1,000.00	$	1,044.30	$	5.83		1.15
Class I-actual return	$	1,000.00	$	1,109.33	$	4.71		0.90
Class I-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
Class R6-actual return	$	1,000.00	$	1,109.90	$	4.45		0.85
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.78	$	4.31		0.85

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Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2021		Ending Account Value 6/30/2021		Expenses Paid During the Period (a)		Annualized Expense Ratio
International Leaders Fund
Class N-actual return	$	1,000.00	$	1,062.14	$	5.88		1.15	%
Class N-hypothetical 5% return	$	1,000.00	$	1,044.30	$	5.83		1.15
Class I-actual return	$	1,000.00	$	1,063.16	$	4.60		0.90
Class I-hypothetical 5% return	$	1,000.00	$	1,045.54	$	4.56		0.90
Class R6-actual return	$	1,000.00	$	1,063.60	$	4.35		0.85
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.78	$	4.31		0.85
International Growth Fund
Class N-actual return	$	1,000.00	$	1,082.84	$	7.49		1.45
Class N-hypothetical 5% return	$	1,000.00	$	1,042.81	$	7.34		1.45
Class I-actual return	$	1,000.00	$	1,084.49	$	5.89		1.14
Class I-hypothetical 5% return	$	1,000.00	$	1,044.35	$	5.78		1.14
Class R6-actual return	$	1,000.00	$	1,084.72	$	5.48		1.06
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.74	$	5.37		1.06
Institutional International Growth Fund
Institutional Class-actual return	$	1,000.00	$	1,084.93	$	5.22		1.01
Institutional Class-hypothetical 5% return	$	1,000.00	$	1,044.99	$	5.12		1.01
International Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,072.78	$	7.55		1.47
Class N-hypothetical 5% return	$	1,000.00	$	1,042.71	$	7.45		1.47
Class I-actual return	$	1,000.00	$	1,074.18	$	6.17		1.20
Class I-hypothetical 5% return	$	1,000.00	$	1,044.05	$	6.08		1.20
Class R6-actual return	$	1,000.00	$	1,074.89	$	5.71		1.11
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.50	$	5.63		1.11
Emerging Markets Leaders Fund
Class N-actual return	$	1,000.00	$	1,036.95	$	7.07		1.40
Class N-hypothetical 5% return	$	1,000.00	$	1,043.06	$	7.09		1.40
Class I-actual return	$	1,000.00	$	1,038.40	$	5.81		1.15
Class I-hypothetical 5% return	$	1,000.00	$	1,044.30	$	5.83		1.15
Class R6-actual return	$	1,000.00	$	1,039.22	$	5.56		1.10
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.55	$	5.58		1.10
Emerging Markets Growth Fund
Class N-actual return	$	1,000.00	$	1,103.69	$	7.93		1.52
Class N-hypothetical 5% return	$	1,000.00	$	1,042.46	$	7.70		1.52
Class I-actual return	$	1,000.00	$	1,105.04	$	6.42		1.23
Class I-hypothetical 5% return	$	1,000.00	$	1,043.90	$	6.23		1.23
Class R6-actual return	$	1,000.00	$	1,105.63	$	6.06		1.16
Class R6-hypothetical 5% return	$	1,000.00	$	1,044.25	$	5.88		1.16
Emerging Markets Small Cap Growth Fund
Class N-actual return	$	1,000.00	$	1,135.46	$	8.21		1.55
Class N-hypothetical 5% return	$	1,000.00	$	1,042.31	$	7.85		1.55
Class I-actual return	$	1,000.00	$	1,137.05	$	6.89		1.30
Class I-hypothetical 5% return	$	1,000.00	$	1,043.55	$	6.59		1.30
Class R6-actual return	$	1,000.00	$	1,137.25	$	6.57		1.24
Class R6-hypothetical 5% return	$	1,000.00	$	1,043.85	$	6.28		1.24
Bond Fund
Class N-actual return	$	1,000.00	$	987.67	$	2.96		0.60
Class N-hypothetical 5% return	$	1,000.00	$	1,047.02	$	3.05		0.60
Class I-actual return	$	1,000.00	$	989.06	$	2.22		0.45
Class I-hypothetical 5% return	$	1,000.00	$	1,047.77	$	2.28		0.45
Class R6-actual return	$	1,000.00	$	988.36	$	1.97		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	$	991.66	$	4.20		0.85
Class N-hypothetical 5% return	$	1,000.00	$	1,045.78	$	4.31		0.85
Class I-actual return	$	1,000.00	$	992.38	$	3.36		0.68
Class I-hypothetical 5% return	$	1,000.00	$	1,046.63	$	3.45		0.68
Class R6-actual return	$	1,000.00	$	992.64	$	3.06		0.62
Class R6-hypothetical 5% return	$	1,000.00	$	1,046.93	$	3.15		0.62

June 30, 2021

William Blair Funds

195

Fund Expenses (Unaudited)

Expense Example	Beginning Account Value 1/1/2021		Ending Account Value 6/30/2021		Expenses Paid During the Period (a)		Annualized Expense Ratio
Low Duration Fund
Class N-actual return	$	1,000.00	$	1,000.48	$	2.73		0.55	%
Class N-hypothetical 5% return	$	1,000.00	$	1,047.27	$	2.79		0.55
Class I-actual return	$	1,000.00	$	1,001.25	$	1.98		0.40
Class I-hypothetical 5% return	$	1,000.00	$	1,048.02	$	2.03		0.40
Class R6-actual return	$	1,000.00	$	1,001.47	$	1.74		0.35
Class R6-hypothetical 5% return	$	1,000.00	$	1,048.26	$	1.78		0.35
Emerging Markets Debt Fund
Class I-actual return (b)	$	1,000.00	$	1,003.69	$	0.71		0.70
Class I-hypothetical 5% return (6 month period)	$	1,000.00	$	1,046.53	$	3.55		0.70
Class R6-actual return (b)	$	1,000.00	$	1,003.73	$	0.66		0.65
Class R6-hypothetical 5% return (6 month period)	$	1,000.00	$	1,046.78	$	3.30		0.65
Macro Allocation Fund
Class N-actual return	$	1,000.00	$	1,038.43	$	6.37		1.26
Class N-hypothetical 5% return	$	1,000.00	$	1,043.75	$	6.38		1.26
Class I-actual return	$	1,000.00	$	1,039.63	$	5.11		1.01
Class I-hypothetical 5% return	$	1,000.00	$	1,044.99	$	5.12		1.01
Class R6-actual return	$	1,000.00	$	1,040.55	$	4.86		0.96
Class R6-hypothetical 5% return	$	1,000.00	$	1,045.24	$	4.87		0.96

(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 25, 2021 (Commencement of Operations) to June 30, 2021.

196

Semiannual Report

June 30, 2021

	BOARD OF TRUSTEES (as of August 26, 2021)

	Vann A. Avedisian
	Co-founder and Partner, Newbond Holdings
	Kathleen T. Barr
	Retired Senior Managing Director, PNC Capital Advisors, LLC
	Stephanie G. Braming, CFA, 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

	Alaina Anderson, CFA, Senior Vice President
	Marcelo Assalin, CFA, Senior Vice President
	Thomas Clarke, Senior Vice President
	Daniel Crowe, CFA, Senior Vice President
	Robert J. Duwa, CFA, Senior Vice President
	Simon Fennell, Senior Vice President
	Andrew G. Flynn, CFA, Senior Vice President
	David C. Fording, CFA, Senior Vice President
	James S. Golan, CFA, Senior Vice President
	William V. Heaphy, CFA, Senior Vice President
	James E. Jones, CFA, Senior Vice President
	Kenneth J. McAtamney, Senior Vice President
	Todd M. McClone, CFA, Senior Vice President
	John C. Murphy, CFA, Senior Vice President
	D.J. Neiman, CFA, Senior Vice President
	Casey K. Preyss, CFA, Senior Vice President
	David P. Ricci, CFA, Senior Vice President
	Lisa D. Rusch, Senior Vice President
	Hugo Scott-Gall, Senior Vice President
	Ward D. Sexton, CFA, Senior Vice President
	Brian D. Singer, CFA, Senior Vice President
	Mark C. Thompson, CFA, Senior Vice President
	Vivian Lin Thurston, CFA, Senior Vice President
	Dan Zelazny, Senior Vice President
	Ruta Ziverte, Senior Vice President
	Kathleen M. Lynch, CFA, Vice President
	Vesta Marks, CFA, CAIA, Vice President
	Gary J. Merwitz, Vice President
	Marco Ruijer, CFA, Vice President
	John M. Raczek, Treasurer
	Andrew T. Pfau, Secretary
	David M. Cihak, 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
	Transfer Agent
	DST Asset Manager Solutions, Inc.
	For customer assistance, call 1-800-635-2886
	P.O. Box 219137
	Kansas City, Missouri 64121-9137

June 30, 2021

William Blair Funds

197


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 Core Fund	International Leaders Fund
Small-Mid Cap Growth Fund	International Growth Fund	EMERGING MARKETS
Small Cap Growth Fund	Institutional International Growth Fund	DEBT
Small Cap Value Fund	International Small Cap Growth Fund	Emerging Markets Debt Fund
	Emerging Markets Leaders Fund
	Emerging Markets Growth Fund	MULTI-ASSET AND
	Emerging Markets Small Cap Growth Fund	ALTERNATIVE
		Macro Allocation 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-End Management 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 officers, 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 Securities Exchange Act of 1934, as amended to date (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 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 of 1940 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 of 1940 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 26, 2021

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 26, 2021

/s/ John M. Raczek

By:

John M. Raczek

Treasurer

(Principal Financial Officer)

Date: August 26, 2021

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