MFS Series Trust I - MFS Value Fund NCSRS Certified semi-annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMN-CSR

CERTIFIED SHAREHOLDER REPORT OF

REGISTERED MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number811-04777

MFS SERIES TRUST I

(Exact name of registrant as specified in charter)

111 Huntington Avenue, Boston, Massachusetts 02199

(Address of principal executive offices) (Zip code)

Christopher R. Bohane

Massachusetts Financial Services Company

111 Huntington Avenue

Boston, Massachusetts 02199

(Name and address of agents for service)

Registrant’s telephone number, including area code: (617)954-5000

Date of fiscal year end: August 31

Date of reporting period: February 29, 2020

ITEM 1.

REPORTS TO STOCKHOLDERS.

Semiannual Report

February 29, 2020

LOGO

MFS® Core Equity Fund

LOGO

Beginning on January 1, 2021, as permitted by regulations adopted by the U.S. Securities and Exchange Commission, paper copies of the fund’s annual and semiannual shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports. Instead, the complete reports will be made available on the fund’s Web site (funds.mfs.com), and you will be notified by mail each time a report is posted and provided with a Web site link to access the report.

If you are already signed up to receive shareholder reports by email, you will not be affected by this change and you need not take any action. You may sign up to receive shareholder reports and other communications from the fund by email by contacting your financial intermediary (such as a broker-dealer or bank) or, if you hold your shares directly with the fund, by calling 1-800-225-2606 or by logging on to MFS Access at mfs.com.

Beginning on January 1, 2019, you may elect to receive all future reports in paper free of charge. Contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. If you invest directly with the fund, you can call 1-800-225-2606 or send an email request to orderliterature@mfs.com to let the fund know that you wish to continue receiving paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held in your account if you invest through your financial intermediary or all funds held with the MFS fund complex if you invest directly.

RGI-SEM

MFS® Core Equity Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			5
Statement of assets and liabilities			13
Statement of operations			15
Statements of changes in net assets			16
Financial highlights			17
Notes to financial statements			27
Proxy voting policies and information			39
Quarterly portfolio disclosure			39
Further information			39
Information about fund contracts and legal claims			39
Provision of financial reports and summary prospectuses			39


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

geopolitical risk along with easier central bank policies — was overwhelmed in February as the health effects of a novel coronavirus,COVID-19, spread beyond China’s borders, ultimately impacting more than 200 countries. The global pandemic prompted many governments to take drastic action to slow the spread of the virus, such as quarantines, school and business closures, and prohibitions on public gatherings. While these are important steps to protect the public health, they come at a cost: rising market volatility and an abrupt decline in economic growth.

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

governments are undertaking unprecedented levels of fiscal stimulus. As uncertainty recedes, these measures can help create a supportive environment and encourage economic recovery. In the aftermath of the crisis, there are likely to be societal changes as households, businesses and governments adjust to a new reality and these alterations could change the investment landscape. Occurrences such as the COVID-19 outbreak demonstrate the importance of having a deep understanding of company fundamentals, and our global research platform has been built to do just that.

Here at MFS®, we aim to help our clients navigate the growing complexity of the markets and world economies. Our long-term investment philosophy and commitment to the responsible allocation of capital allow us to tune out the noise and uncover what we believe are the best, most durable investment opportunities in the market. Through our powerful global investment platform, we combine collective expertise, thoughtful risk management, and long-term discipline to create sustainable value for investors.

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Apple, Inc.			4.9%
Microsoft Corp.			4.2%
Amazon.com, Inc.			3.4%
Alphabet, Inc., “A”			3.2%
Johnson & Johnson			2.2%
Aon PLC			2.1%
Visa, Inc., “A”			2.0%
Facebook, Inc., “A”			2.0%
American Tower Corp., REIT			1.7%
Salesforce.com, Inc.			1.6%


Global equity sectors (k)
Technology			27.5%
Financial Services			17.6%
Health Care (s)			14.1%
Consumer Cyclicals			12.0%
Capital Goods (s)			11.8%
Energy			6.7%
Consumer Staples			5.1%
Telecommunications/Cable Television (s)			3.9%

(k)	The sectors set forth above and the associated portfolio composition are based on MFS’ own custom sector classification methodology.

(s)	Includes securities sold short.

Cash & Cash Equivalents includes any cash, investments in money market funds, short-term securities, and other assets less liabilities. Please see the Statement of Assets and Liabilities for additional information related to the fund’s cash position and other assets and liabilities.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

As a shareholder of the fund, you incur two types of costs: (1) transaction costs, including sales charges (loads) on certain purchase or redemption payments, and (2) ongoing costs, including management fees; distribution and service(12b-1) fees; and other fund expenses. This 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.

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

The first line for each share class in the following table provides information about actual account values and actual expenses. 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 (for 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 Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes

The second line for each share class in the following 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, which is not the fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period. You may use this information to compare the ongoing costs of investing in the fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the table are meant to highlight your ongoing costs only and do not reflect any transactional costs, such as sales charges (loads). Therefore, the second line for each share class in the table is useful in comparing ongoing costs only, and will not help you determine the relative total costs of owning different funds. In addition, if these transactional costs were included, your costs would have been higher.

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		0.94%		$1,000.00		$1,015.03		$4.71
A	Hypothetical (h)		0.94%		$1,000.00		$1,020.19		$4.72
B	Actual		1.69%		$1,000.00		$1,011.48		$8.45
B	Hypothetical (h)		1.69%		$1,000.00		$1,016.46		$8.47
C	Actual		1.69%		$1,000.00		$1,011.22		$8.45
C	Hypothetical (h)		1.69%		$1,000.00		$1,016.46		$8.47
I	Actual		0.69%		$1,000.00		$1,016.61		$3.46
I	Hypothetical (h)		0.69%		$1,000.00		$1,021.43		$3.47
R1	Actual		1.69%		$1,000.00		$1,011.27		$8.45
R1	Hypothetical (h)		1.69%		$1,000.00		$1,016.46		$8.47
R2	Actual		1.18%		$1,000.00		$1,013.98		$5.91
R2	Hypothetical (h)		1.18%		$1,000.00		$1,019.00		$5.92
R3	Actual		0.94%		$1,000.00		$1,015.13		$4.71
R3	Hypothetical (h)		0.94%		$1,000.00		$1,020.19		$4.72
R4	Actual		0.69%		$1,000.00		$1,016.35		$3.46
R4	Hypothetical (h)		0.69%		$1,000.00		$1,021.43		$3.47
R6	Actual		0.62%		$1,000.00		$1,016.76		$3.11
R6	Hypothetical (h)		0.62%		$1,000.00		$1,021.78		$3.12

(h)	5% class return per year before expenses.

(p)

“Expenses Paid During Period” are equal to each class’s annualized expense ratio, as shown above, multiplied by the average account value over the period, multiplied by 182/366 (to reflect theone-half year period). Expenses paid do not include any applicable sales charges (loads). If these transaction costs had been included, your costs would have been higher.

Notes to Expense Table

Expense ratios include 0.03% of investment related expenses from short sales (See Note 2 of the Notes to Financial Statements). Each class with a Rule12b-1 service fee is subject to a rebate of a portion of such fee. Such rebates are included in the expense ratios above. For Class A and Class R2 shares, this rebate reduced the expense ratios above by 0.01%. See Note 3 in the Notes to Financial Statements for additional information.

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 99.1%
Aerospace - 3.6%
CACI International, Inc., “A” (a)		28,276	$	6,928,186
Curtiss-Wright Corp.		46,685		5,599,399
Honeywell International, Inc.		223,516		36,247,590
Huntington Ingalls Industries, Inc.		24,244		4,982,869
L3Harris Technologies, Inc.		61,281		12,117,092
Northrop Grumman Corp.		52,786		17,358,148
PAE, Inc. (a)		706,683		7,738,179
United Technologies Corp.		226,927		29,634,397

			$	120,605,860
Alcoholic Beverages - 0.3%
Constellation Brands, Inc., “A”		60,030	$	10,347,971

Automotive - 0.6%
Copart, Inc. (a)		100,793	$	8,514,993
IAA, Inc. (a)		82,130		3,508,593
Lear Corp.		55,942		6,220,750
Stoneridge, Inc. (a)		157,777		3,486,872

			$	21,731,208
Biotechnology - 0.4%
Adaptive Biotechnologies Corp. (a)		65,354	$	1,836,448
Illumina, Inc. (a)		48,814		12,968,415

			$	14,804,863
Broadcasting - 0.6%
Netflix, Inc. (a)		52,137	$	19,240,117

Brokerage & Asset Managers - 1.8%
Charles Schwab Corp.		968,536	$	39,467,842
NASDAQ, Inc.		187,807		19,259,608

			$	58,727,450
Business Services - 3.8%
Accenture PLC, “A”		54,998	$	9,932,089
Amdocs Ltd.		131,519		8,384,336
Clarivate Analytics PLC (a)		1,164,376		23,683,408
Fidelity National Information Services, Inc.		145,925		20,388,641
Fiserv, Inc. (a)		150,533		16,462,289
Global Payments, Inc.		112,375		20,673,628
Verisk Analytics, Inc., “A”		171,845		26,654,878

			$	126,179,269

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Cable TV - 1.3%
Cable One, Inc.		2,601	$	4,091,425
Charter Communications, Inc., “A” (a)		67,075		33,079,378
Comcast Corp., “A”		188,673		7,628,049

			$	44,798,852
Chemicals - 0.3%
FMC Corp.		72,639	$	6,762,691
Ingevity Corp. (a)		56,479		2,543,814

			$	9,306,505
Computer Software - 8.3%
Adobe Systems, Inc. (a)		138,527	$	47,808,438
Black Knight, Inc. (a)		149,886		9,998,895
Cadence Design Systems, Inc. (a)		226,688		14,993,144
Everbridge, Inc. (a)		115,851		12,240,817
Microsoft Corp.		864,975		140,134,600
Salesforce.com, Inc. (a)		306,274		52,189,090

			$	277,364,984
Computer Software - Systems - 6.7%
Apple, Inc. (s)		601,388	$	164,395,424
EPAM Systems, Inc. (a)		49,263		10,995,501
Rapid7, Inc. (a)		178,863		8,281,357
ServiceNow, Inc. (a)		63,376		20,666,280
Square, Inc., “A” (a)		100,057		8,337,750
Zebra Technologies Corp., “A” (a)		44,581		9,405,253

			$	222,081,565
Construction - 1.1%
Masco Corp.		176,617	$	7,297,815
Toll Brothers, Inc.		580,494		21,495,693
Vulcan Materials Co.	��	69,001		8,298,060

			$	37,091,568
Consumer Products - 1.5%
Colgate-Palmolive Co.		229,848	$	15,530,830
Energizer Holdings, Inc.		48,098		2,067,733
Kimberly-Clark Corp.		107,343		14,082,328
Procter & Gamble Co.		153,009		17,325,209

			$	49,006,100
Consumer Services - 0.8%
Booking Holdings, Inc. (a)		5,905	$	10,012,872
Bright Horizons Family Solutions, Inc. (a)		50,066		7,867,872

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Consumer Services - continued
Grand Canyon Education, Inc. (a)		100,296	$	8,091,881

			$	25,972,625
Containers - 0.2%
Ball Corp.		50,270	$	3,542,024
Sealed Air Corp.		127,822		3,874,285

			$	7,416,309
Electrical Equipment - 1.8%
AMETEK, Inc.		262,259	$	22,554,274
Fortive Corp.		208,204		14,399,389
HD Supply Holdings, Inc. (a)		255,061		9,697,419
Sensata Technologies Holding PLC (a)		225,150		9,186,120
TE Connectivity Ltd.		68,535		5,679,495

			$	61,516,697
Electronics - 3.1%
Analog Devices, Inc.		161,195	$	17,578,315
Applied Materials, Inc.		119,697		6,956,790
Marvell Technology Group Ltd.		502,798		10,709,597
Mellanox Technologies Ltd. (a)		39,113		4,670,874
Monolithic Power Systems, Inc.		28,009		4,443,348
nLIGHT, Inc. (a)		131,050		2,163,636
NXP Semiconductors N.V.		237,926		27,049,807
Silicon Laboratories, Inc. (a)		42,877		3,802,332
Texas Instruments, Inc.		231,134		26,381,635

			$	103,756,334
Energy - Independent - 1.2%
ConocoPhillips		275,934	$	13,360,724
Diamondback Energy, Inc.		81,162		5,032,044
Pioneer Natural Resources Co.		59,232		7,272,505
Valero Energy Corp.		236,163		15,645,799

			$	41,311,072
Energy - Integrated - 1.3%
Chevron Corp.		472,431	$	44,096,710

Engineering - Construction - 0.2%
KBR, Inc.		225,395	$	5,851,254

Food & Beverages - 2.8%
Archer Daniels Midland Co.		220,979	$	8,319,859
Coca-Cola Co.		134,187		7,177,663
Coca-Cola European Partners PLC		127,563		6,500,611

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Food & Beverages - continued
Hostess Brands, Inc. (a)		431,244	$	5,481,111
J.M. Smucker Co.		55,161		5,681,031
Mondelez International, Inc.		438,781		23,167,637
Nomad Foods Ltd. (a)		163,076		3,010,383
PepsiCo, Inc.		250,033		33,011,857

			$	92,350,152
Food & Drug Stores - 1.0%
Wal-Mart Stores, Inc.		303,609	$	32,692,617

Gaming & Lodging - 0.8%
Marriott International, Inc., “A”		141,885	$	17,593,740
Wyndham Hotels & Resorts, Inc.		208,782		10,637,443

			$	28,231,183
General Merchandise - 1.7%
Dollar General Corp.		158,488	$	23,820,747
Dollar Tree, Inc. (a)		233,969		19,426,446
Ollie’s Bargain Outlet Holdings, Inc. (a)		240,274		12,222,738

			$	55,469,931
Health Maintenance Organizations - 1.6%
Cigna Corp.		160,418	$	29,346,869
Humana, Inc.		71,336		22,804,692

			$	52,151,561
Insurance - 4.3%
Aon PLC		343,705	$	71,490,640
Assurant, Inc.		92,698		11,178,452
Chubb Ltd.		157,966		22,909,809
Everest Re Group Ltd.		24,899		6,171,964
Hartford Financial Services Group, Inc.		231,259		11,551,387
MetLife, Inc.		213,096		9,103,461
Reinsurance Group of America, Inc.		44,285		5,404,099
Third Point Reinsurance Ltd. (a)		809,181		7,217,894

			$	145,027,706
Internet - 5.2%
Alphabet, Inc., “A” (a)(s)		78,821	$	105,561,024
Facebook, Inc., “A” (a)		347,652		66,912,581

			$	172,473,605
Leisure & Toys - 0.6%
Electronic Arts, Inc. (a)		195,755	$	19,843,684

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Machinery & Tools - 1.2%
Flowserve Corp.		209,505	$	8,420,006
IDEX Corp.		38,014		5,626,072
ITT, Inc.		94,096		5,659,874
Roper Technologies, Inc.		55,922		19,667,768

			$	39,373,720
Major Banks - 1.9%
Goldman Sachs Group, Inc.		219,043	$	43,977,263
PNC Financial Services Group, Inc.		163,409		20,654,898

			$	64,632,161
Medical & Health Technology & Services - 1.5%
Guardant Health, Inc. (a)		21,497	$	1,869,379
HCA Healthcare, Inc.		112,901		14,339,556
HealthEquity, Inc. (a)		132,413		9,399,999
McKesson Corp.		73,006		10,210,619
PRA Health Sciences, Inc. (a)		106,449		10,027,496
Premier, Inc., “A” (a)		193,114		5,683,345

			$	51,530,394
Medical Equipment - 4.1%
Becton, Dickinson and Co.		85,967	$	20,444,672
Boston Scientific Corp. (a)		563,264		21,060,441
Danaher Corp.		98,136		14,188,503
Masimo Corp. (a)		39,942		6,523,727
Medtronic PLC		367,264		36,972,467
PerkinElmer, Inc.		206,554		17,854,528
STERIS PLC		81,262		12,889,778
West Pharmaceutical Services, Inc.		44,552		6,707,749

			$	136,641,865
Natural Gas - Pipeline - 0.4%
Enterprise Products Partners LP		368,563	$	8,602,260
Equitrans Midstream Corp.		470,150		3,319,259

			$	11,921,519
Network & Telecom - 0.5%
Equinix, Inc., REIT		22,384	$	12,821,555
Interxion Holding N.V. (a)		53,909		4,576,335

			$	17,397,890
Oil Services - 0.3%
Cactus, Inc., “A”		99,216	$	2,709,589
Core Laboratories N.V.		131,962		3,541,860

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Oil Services - continued
Patterson-UTI Energy, Inc.		736,522	$	4,220,271

			$	10,471,720
Other Banks & Diversified Financials - 6.7%
Bank OZK		335,384	$	8,515,400
Citigroup, Inc.		666,430		42,291,648
Northern Trust Corp.		116,347		10,210,613
Prosperity Bancshares, Inc.		53,491		3,455,518
S&P Global, Inc.		44,087		11,723,174
SLM Corp.		1,214,331		12,592,612
SVB Financial Group (a)		19,286		4,014,574
Truist Financial Corp.		743,917		34,324,330
U.S. Bancorp		633,591		29,423,966
Visa, Inc., “A”		369,364		67,135,601

			$	223,687,436
Pharmaceuticals - 6.8%
Elanco Animal Health, Inc. (a)		740,079	$	20,278,165
Eli Lilly & Co.		331,061		41,756,724
Johnson & Johnson		557,284		74,943,552
Merck & Co., Inc.		548,045		41,958,325
Zoetis, Inc.		352,136		46,915,079

			$	225,851,845
Pollution Control - 0.3%
Waste Connections, Inc.		107,538	$	10,376,342

Railroad & Shipping - 1.2%
Canadian National Railway Co.		229,936	$	19,523,866
Canadian Pacific Railway Ltd.		82,002		20,399,637

			$	39,923,503
Real Estate - 2.6%
EPR Properties, REIT		225,672	$	13,368,809
Industrial Logistics Properties Trust, REIT		571,102		11,798,967
Lexington Realty Trust, REIT		517,840		5,370,001
Medical Properties Trust, Inc., REIT		956,973		20,220,840
STORE Capital Corp., REIT		413,774		13,596,614
Sun Communities, Inc., REIT		34,381		5,256,167
W.P. Carey, Inc., REIT		239,762		18,559,976

			$	88,171,374

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Restaurants - 1.1%
Starbucks Corp.		357,138	$	28,010,333
U.S. Foods Holding Corp. (a)		234,658		7,893,895

			$	35,904,228
Specialty Chemicals - 1.5%
Axalta Coating Systems Ltd. (a)		639,746	$	15,942,470
Corteva, Inc.		404,126		10,992,227
DuPont de Nemours, Inc.		249,331		10,696,300
Element Solutions, Inc. (a)		611,195		6,350,316
Univar Solutions, Inc. (a)		268,715		4,565,468

			$	48,546,781
Specialty Stores - 5.3%
Amazon.com, Inc. (a)(s)		59,955	$	112,940,231
Burlington Stores, Inc. (a)		86,323		18,668,212
Ross Stores, Inc.		182,830		19,888,248
Target Corp.		237,026		24,413,678

			$	175,910,369
Telecommunications - Wireless - 1.7%
American Tower Corp., REIT		251,142	$	56,959,006

Telephone Services - 1.0%
Verizon Communications, Inc.		640,813	$	34,706,432

Tobacco - 0.6%
Philip Morris International, Inc.		229,942	$	18,825,352

Trucking - 0.2%
Forward Air Corp.		113,360	$	6,689,374

Utilities - Electric Power - 3.3%
American Electric Power Co., Inc.		170,879	$	15,252,659
CenterPoint Energy, Inc.		366,310		8,432,456
CMS Energy Corp.		208,018		12,568,448
Duke Energy Corp.		40,151		3,681,847
Evergy, Inc.		198,983		13,003,539
Exelon Corp.		294,540		12,697,619
NextEra Energy, Inc.		99,693		25,198,403
Southern Co.		105,116		6,344,802
Xcel Energy, Inc.		224,916		14,016,765

			$	111,196,538
Total Common Stocks (Identified Cost, $2,785,824,455)			$	3,308,165,601

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par			Value ($)
Convertible Preferred Stocks - 0.1%
Natural Gas - Distribution - 0.1%
South Jersey Industries, Inc.		40,507		$	1,866,562

Utilities - Electric Power - 0.0%
American Electric Power Co., Inc.		14,450		$	749,666
Total Convertible Preferred Stocks (Identified Cost, $2,755,559)				$	2,616,228

Investment Companies (h) - 1.7%
Money Market Funds - 1.7%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $59,061,157)		59,063,086		$	59,068,993

Securities Sold Short - (0.5)%
Medical & Health Technology & Services - (0.3)%
Healthcare Services Group, Inc.		(326,437	)	$	(8,990,075	)

Telecommunications - Wireless - (0.2)%
Crown Castle International Corp., REIT		(44,300	)	$	(6,347,747	)

Trucking - (0.0)%
XPO Logistics, Inc. (s)		(25,219	)	$	(1,865,449	)
Total Securities Sold Short (Proceeds Received, $15,997,832)				$	(17,203,271	)

Other Assets, Less Liabilities - (0.4)%				(14,582,263)
Net Assets - 100.0%				$	3,338,065,288

(a)	Non-income producing security.

(h)

An affiliated issuer, which may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under common control. At period end, the aggregate values of the fund’s investments in affiliated issuers and in unaffiliated issuers were $59,068,993 and $3,310,781,829, respectively.

(s)	Security or a portion of the security was pledged to cover collateral requirements for securities sold short.

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

REIT

Real Estate Investment Trust

At February 29, 2020, the fund had cash collateral of $360,281 and other liquid securities with an aggregate value of $38,173,252 to cover any collateral or margin obligations for securities sold short. Restricted cash and/or deposits with brokers in the Statement of Assets and Liabilities are comprised of cash collateral.

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value (identified cost, $2,788,580,014)			$3,310,781,829
Investments in affiliated issuers, at value (identified cost, $59,061,157)			59,068,993
Deposits with brokers for
Securities sold short			360,281
Receivables for
Investments sold			6,674,162
Fund shares sold			13,264,505
Dividends			5,635,461
Other assets			10,358
Total assets			$3,395,795,589

Liabilities
Payables for
Dividends on securities sold short			$65,695
Securities sold short, at value (proceeds received, $15,997,832)			17,203,271
Investments purchased			10,272,096
Fund shares reacquired			28,958,218
Payable to affiliates
Investment adviser			152,270
Administrative services fee			3,790
Shareholder servicing costs			913,861
Distribution and service fees			38,411
Payable for independent Trustees’ compensation			11,328
Accrued expenses and other liabilities			111,361
Total liabilities			$57,730,301
Net assets			$3,338,065,288

Net assets consist of
Paid-in capital			$2,717,263,982
Total distributable earnings (loss)			620,801,306
Net assets			$3,338,065,288
Shares of beneficial interest outstanding			101,126,358

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$1,569,612,604		48,546,895		$32.33
Class B		25,651,692		913,336		28.09
Class C		113,619,437		4,108,930		27.65
Class I		584,016,463		16,994,642		34.36
Class R1		3,044,112		109,931		27.69
Class R2		13,829,254		438,666		31.53
Class R3		53,811,492		1,669,232		32.24
Class R4		30,288,720		928,182		32.63
Class R6		944,191,514		27,416,544		34.44

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $34.30 [100 / 94.25 x $32.33]. On sales of $50,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$24,996,402
Dividends from affiliated issuers	449,718
Other	219,155
Income on securities loaned	83,209
Foreign taxes withheld	(51,600	)
Total investment income	$25,696,884
Expenses
Management fee	$9,126,281
Distribution and service fees	2,759,222
Shareholder servicing costs	1,171,201
Administrative services fee	216,859
Independent Trustees’ compensation	21,850
Custodian fee	60,878
Shareholder communications	73,119
Audit and tax fees	29,386
Legal fees	12,127
Dividend and interest expense on securities sold short	423,285
Interest expense and fees	7,605
Miscellaneous	154,308
Total expenses	$14,056,121
Reduction of expenses by investment adviser and distributor	(212,536	)
Net expenses	$13,843,585
Net investment income (loss)	$11,853,299

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$95,799,500
Affiliated issuers	(5,208	)
Foreign currency	408
Net realized gain (loss)	$95,794,700
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$(75,754,128	)
Affiliated issuers	1,628
Securities sold short	(1,446,279	)
Net unrealized gain (loss)	$(77,198,779	)
Net realized and unrealized gain (loss)	$18,595,921
Change in net assets from operations	$30,449,220

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$11,853,299			$17,641,294
Net realized gain (loss)		95,794,700			45,641,322
Net unrealized gain (loss)		(77,198,779	)		74,564,469
Change in net assets from operations		$30,449,220			$137,847,085
Total distributions to shareholders		$(63,849,491	)		$(199,800,134	)
Change in net assets from fund share transactions		$563,871,815			$695,524,955
Total change in net assets		$530,471,544			$633,571,906

Net assets
At beginning of period		2,807,593,744			2,174,021,838
At end of period		$3,338,065,288			$2,807,593,744

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS

The financial highlights table is intended to help you understand the fund’s financial performance for the semiannual period and the past 5 fiscal years. Certain information reflects financial results for a single fund share. The total returns in the table represent the rate that an investor would have earned (or lost) on an investment in the fund share class (assuming reinvestment of all distributions) held for the entire period.


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$32.45			$34.18			$30.46			$26.72			$27.19			$29.19

Income (loss) from investment operations
Net investment income (loss) (d)		$0.11			$0.20			$0.20			$0.18	(c)		$0.18			$0.15
Net realized and unrealized gain (loss)		0.41			1.05			5.63			4.53			2.08			0.13
Total from investment operations		$0.52			$1.25			$5.83			$4.71			$2.26			$0.28

Less distributions declared to shareholders
From net investment income		$(0.15	)		$(0.16	)		$(0.17	)		$(0.16	)		$(0.14	)		$(0.13	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.64	)		$(2.98	)		$(2.11	)		$(0.97	)		$(2.73	)		$(2.28	)
Net asset value, end of period (x)		$32.33			$32.45			$34.18			$30.46			$26.72			$27.19
Total return (%) (r)(s)(t)(x)		1.50	(n)		4.94			19.89			18.11	(c)		9.09			0.98

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.95	(a)		1.00			1.00			1.03	(c)		1.07			1.05
Expenses after expense reductions (f)		0.94	(a)		0.98			0.99			1.01	(c)		1.05			1.04
Net investment income (loss)		0.62	(a)		0.65			0.62			0.63	(c)		0.70			0.52
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$1,569,613			$1,373,524			$1,184,976			$992,736			$959,812			$963,167

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.91	(a)		0.96			0.97			1.00	(c)		1.04			1.03

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$28.23			$30.19			$27.17			$23.96			$24.70			$26.78

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.02	)		$(0.03	)		$(0.04	)		$(0.03	)(c)		$(0.02	)		$(0.06	)
Net realized and unrealized gain (loss)		0.37			0.89			5.00			4.05			1.87			0.13
Total from investment operations		$0.35			$0.86			$4.96			$4.02			$1.85			$0.07

Less distributions declared to shareholders
From net investment income		$—			$—			$—			$—			$—			$—
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.49	)		$(2.82	)		$(1.94	)		$(0.81	)		$(2.59	)		$(2.15	)
Net asset value, end of period (x)		$28.09			$28.23			$30.19			$27.17			$23.96			$24.70
Total return (%) (r)(s)(t)(x)		1.15	(n)		4.16			19.01			17.21	(c)		8.24			0.25

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.70	(a)		1.75			1.75			1.78	(c)		1.82			1.80
Expenses after expense reductions (f)		1.69	(a)		1.73			1.74			1.77	(c)		1.81			1.80
Net investment income (loss)		(0.13	)(a)		(0.11	)		(0.14	)		(0.12	)(c)		(0.07	)		(0.23	)
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$25,652			$22,759			$26,993			$27,139			$30,324			$34,126

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.66	(a)		1.71			1.72			1.75	(c)		1.79			1.79

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$27.86			$29.84			$26.88			$23.71			$24.47			$26.55

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.02	)		$(0.03	)		$(0.05	)		$(0.03	)(c)		$(0.01	)		$(0.06	)
Net realized and unrealized gain (loss)		0.36			0.87			4.95			4.01			1.84			0.13
Total from investment operations		$0.34			$0.84			$4.90			$3.98			$1.83			$0.07

Less distributions declared to shareholders
From net investment income		$(0.06	)		$—			$—			$—			$—			$—
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.55	)		$(2.82	)		$(1.94	)		$(0.81	)		$(2.59	)		$(2.15	)
Net asset value, end of period (x)		$27.65			$27.86			$29.84			$26.88			$23.71			$24.47
Total return (%) (r)(s)(t)(x)		1.12	(n)		4.14			18.98			17.22	(c)		8.24			0.26

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.70	(a)		1.75			1.75			1.78	(c)		1.82			1.80
Expenses after expense reductions (f)		1.69	(a)		1.74			1.74			1.77	(c)		1.81			1.80
Net investment income (loss)		(0.11	)(a)		(0.10	)		(0.17	)		(0.12	)(c)		(0.05	)		(0.23	)
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$113,619			$72,093			$56,413			$89,946			$89,160			$88,020

Supplemental Ratios (%):											��
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.67	(a)		1.71			1.72			1.75	(c)		1.79			1.79

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$34.47			$36.12			$32.07			$28.10			$28.44			$30.43

Income (loss) from investment operations
Net investment income (loss) (d)		$0.16			$0.30			$0.30			$0.26	(c)		$0.29			$0.23
Net realized and unrealized gain (loss)		0.44			1.11			5.93			4.76			2.15			0.13
Total from investment operations		$0.60			$1.41			$6.23			$5.02			$2.44			$0.36

Less distributions declared to shareholders
From net investment income		$(0.22	)		$(0.24	)		$(0.24	)		$(0.24	)		$(0.19	)		$(0.20	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.71	)		$(3.06	)		$(2.18	)		$(1.05	)		$(2.78	)		$(2.35	)
Net asset value, end of period (x)		$34.36			$34.47			$36.12			$32.07			$28.10			$28.44
Total return (%) (r)(s)(t)(x)		1.63	(n)		5.17			20.21			18.38	(c)		9.36			1.23

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.70	(a)		0.75			0.75			0.78	(c)		0.81			0.80
Expenses after expense reductions (f)		0.69	(a)		0.74			0.74			0.77	(c)		0.80			0.80
Net investment income (loss)		0.87	(a)		0.90			0.88			0.88	(c)		1.07			0.77
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$584,016			$467,860			$246,779			$122,055			$61,739			$49,768

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.67	(a)		0.72			0.73			0.75	(c)		0.79			0.79

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$27.84			$29.82			$26.86			$23.70			$24.45			$26.54

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.02	)		$(0.03	)		$(0.04	)		$(0.03	)(c)		$(0.02	)		$(0.06	)
Net realized and unrealized gain (loss)		0.36			0.87			4.94			4.00			1.86			0.12
Total from investment operations		$0.34			$0.84			$4.90			$3.97			$1.84			$0.06

Less distributions declared to shareholders
From net investment income		$—			$—			$—			$—			$—			$—
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.49	)		$(2.82	)		$(1.94	)		$(0.81	)		$(2.59	)		$(2.15	)
Net asset value, end of period (x)		$27.69			$27.84			$29.82			$26.86			$23.70			$24.45
Total return (%) (r)(s)(t)(x)		1.13	(n)		4.14			19.00			17.19	(c)		8.29			0.22

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.70	(a)		1.75			1.75			1.78	(c)		1.82			1.80
Expenses after expense reductions (f)		1.69	(a)		1.74			1.74			1.77	(c)		1.81			1.80
Net investment income (loss)		(0.15	)(a)		(0.11	)		(0.14	)		(0.13	)(c)		(0.09	)		(0.23	)
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$3,044			$3,186			$3,448			$3,103			$2,935			$3,625

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.67	(a)		1.71			1.73			1.75	(c)		1.80			1.79

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$31.61			$33.33			$29.75			$26.12			$26.62			$28.59

Income (loss) from investment operations
Net investment income (loss) (d)		$0.06			$0.12			$0.11			$0.10	(c)		$0.11			$0.07
Net realized and unrealized gain (loss)		0.41			1.02			5.50			4.43			2.04			0.14
Total from investment operations		$0.47			$1.14			$5.61			$4.53			$2.15			$0.21

Less distributions declared to shareholders
From net investment income		$(0.06	)		$(0.04	)		$(0.09	)		$(0.09	)		$(0.06	)		$(0.03	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.55	)		$(2.86	)		$(2.03	)		$(0.90	)		$(2.65	)		$(2.18	)
Net asset value, end of period (x)		$31.53			$31.61			$33.33			$29.75			$26.12			$26.62
Total return (%) (r)(s)(t)(x)		1.40	(n)		4.66			19.61			17.80	(c)		8.82			0.75

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.20	(a)		1.25			1.25			1.28	(c)		1.32			1.30
Expenses after expense reductions (f)		1.18	(a)		1.23			1.24			1.27	(c)		1.31			1.30
Net investment income (loss)		0.36	(a)		0.39			0.35			0.38	(c)		0.46			0.27
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$13,829			$13,416			$15,202			$16,508			$15,932			$16,332

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.16	(a)		1.20			1.22			1.25	(c)		1.29			1.29

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$32.36			$34.11			$30.33			$26.61			$27.10			$29.10

Income (loss) from investment operations
Net investment income (loss) (d)		$0.11			$0.20			$0.20			$0.17	(c)		$0.18			$0.15
Net realized and unrealized gain (loss)		0.41			1.04			5.61			4.52			2.06			0.13
Total from investment operations		$0.52			$1.24			$5.81			$4.69			$2.24			$0.28

Less distributions declared to shareholders
From net investment income		$(0.15	)		$(0.17	)		$(0.09	)		$(0.16	)		$(0.14	)		$(0.13	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.64	)		$(2.99	)		$(2.03	)		$(0.97	)		$(2.73	)		$(2.28	)
Net asset value, end of period (x)		$32.24			$32.36			$34.11			$30.33			$26.61			$27.10
Total return (%) (r)(s)(t)(x)		1.51	(n)		4.91			19.91			18.10	(c)		9.06			0.99

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.95	(a)		1.00			1.00			1.02	(c)		1.07			1.05
Expenses after expense reductions (f)		0.94	(a)		0.99			0.99			1.02	(c)		1.06			1.05
Net investment income (loss)		0.62	(a)		0.64			0.61			0.62	(c)		0.71			0.52
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$53,811			$42,199			$34,916			$28,075			$77,217			$65,775

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.92	(a)		0.96			0.98			1.00	(c)		1.04			1.04

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$32.76			$34.48			$30.71			$26.93			$27.39			$29.40

Income (loss) from investment operations
Net investment income (loss) (d)		$0.15			$0.28			$0.28			$0.25	(c)		$0.23			$0.22
Net realized and unrealized gain (loss)		0.42			1.05			5.67			4.57			2.11			0.12
Total from investment operations		$0.57			$1.33			$5.95			$4.82			$2.34			$0.34

Less distributions declared to shareholders
From net investment income		$(0.21	)		$(0.23	)		$(0.24	)		$(0.23	)		$(0.21	)		$(0.20	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.70	)		$(3.05	)		$(2.18	)		$(1.04	)		$(2.80	)		$(2.35	)
Net asset value, end of period (x)		$32.63			$32.76			$34.48			$30.71			$26.93			$27.39
Total return (%) (r)(s)(t)(x)		1.64	(n)		5.18			20.18			18.40	(c)		9.36			1.22

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.70	(a)		0.75			0.75			0.78	(c)		0.82			0.80
Expenses after expense reductions (f)		0.69	(a)		0.74			0.74			0.77	(c)		0.81			0.80
Net investment income (loss)		0.85	(a)		0.89			0.86			0.87	(c)		0.90			0.76
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$30,289			$29,218			$27,707			$22,494			$15,799			$21,159

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.67	(a)		0.71			0.73			0.76	(c)		0.79			0.79

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$34.55			$36.18			$32.12			$28.13			$28.49			$30.47

Income (loss) from investment operations
Net investment income (loss) (d)		$0.17			$0.32			$0.32			$0.29	(c)		$0.58			$0.24
Net realized and unrealized gain (loss)		0.44			1.13			5.95			4.77			1.89			0.15
Total from investment operations		$0.61			$1.45			$6.27			$5.06			$2.47			$0.39

Less distributions declared to shareholders
From net investment income		$(0.23	)		$(0.26	)		$(0.27	)		$(0.27	)		$(0.24	)		$(0.22	)
From net realized gain		(0.49	)		(2.82	)		(1.94	)		(0.81	)		(2.59	)		(2.15	)
Total distributions declared to shareholders		$(0.72	)		$(3.08	)		$(2.21	)		$(1.07	)		$(2.83	)		$(2.37	)
Net asset value, end of period (x)		$34.44			$34.55			$36.18			$32.12			$28.13			$28.49
Total return (%) (r)(s)(t)(x)		1.68	(n)		5.28			20.29			18.49	(c)		9.46			1.34

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.63	(a)		0.67			0.67			0.69	(c)		0.70			0.71
Expenses after expense reductions (f)		0.62	(a)		0.66			0.66			0.68	(c)		0.69			0.70
Net investment income (loss)		0.93	(a)		0.98			0.95			0.97	(c)		2.10			0.82
Portfolio turnover		24	(n)		39			42			46			68			53
Net assets at end of period (000 omitted)		$944,192			$783,340			$577,588			$393,153			$300,078			$6,198

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.60	(a)		0.63			0.65			0.66	(c)		0.68			0.69

See Notes to Financial Statements

Financial Highlights – continued

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)

From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower. Excluding the effect of the proceeds received from anon-recurring litigation settlement against Household International, Inc., the total return for the year ended August 31, 2017 would have been lower by approximately 0.85%.

(t)	Total returns do not include any applicable sales charges.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Core Equity Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

The fund is an investment company and accordingly follows the investment company accounting and reporting guidance of the Financial Accounting Standards Board (FASB) Accounting Standards Codification Topic 946 Financial Services - Investment Companies.

(2) Significant Accounting Policies

In March 2020, the FASB issued Accounting Standards Update2020-04, Reference Rate Reform (Topic 848) – Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU2020-04”), which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the London Interbank Offered Rate (LIBOR) and other IBOR-based reference rates as of the end of 2021. The temporary relief provided by ASU2020-04 is effective for certain reference rate-related contract modifications that occur during the period from March 12, 2020 through December 31, 2022. Management is evaluating the impact of ASU2020-04 on the fund’s investments, derivatives, debt and other contracts that will undergo reference rate-related modifications as a result of the reference rate reform.

Balance Sheet Offsetting– The fund’s accounting policy with respect to balance sheet offsetting is that, absent an event of default by the counterparty or a termination of the agreement, the International Swaps and Derivatives Association (ISDA) Master Agreement, or similar agreement, does not result in an offset of reported amounts of financial assets and financial liabilities in the Statement of Assets and Liabilities across transactions between the fund and the applicable counterparty. The fund’s right to setoff may be restricted or prohibited by the bankruptcy or insolvency laws of the particular jurisdiction to which a specific master netting agreement counterparty is subject. Balance sheet offsetting disclosures, to the extent applicable to the fund, have been included in the fund’s Significant Accounting Policies note under the captions for each of the fund’sin-scope financial instruments and transactions.

Notes to Financial Statements (unaudited) – continued

securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Equity securities sold short, for which there were no sales reported for that day, are generally valued at the last quoted daily ask quotation on their primary market or exchange as provided by a third-party pricing service.Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

The Board of Trustees has delegated primary responsibility for determining or causing to be determined the value of the fund’s investments (including any fair valuation) to the adviser pursuant to valuation policies and procedures approved by the Board. If the adviser determines that reliable market quotations are not readily available, investments are valued at fair value as determined in good faith by the adviser in accordance with such procedures under the oversight of the Board of Trustees. Under the fund’s valuation policies and procedures, market quotations are not considered to be readily available for most types of debt instruments and floating rate loans and many types of derivatives. These investments are generally valued at fair value based on information from third-party pricing services. In addition, investments may be valued at fair value if the adviser determines that an investment’s value has been materially affected by events occurring after the close of the exchange or market on which the investment is principally traded (such as foreign exchange or market) and prior to the determination of the fund’s net asset value, or after the halt of trading of a specific security where trading does not resume prior to the close of the exchange or market on which the security is principally traded. Events that occur after foreign markets close (such as developments in foreign markets and significant movements in the U.S. markets) and prior to the determination of the fund’s net asset value may be deemed to have a material effect on the value of securities traded in foreign markets. Accordingly, the fund’s foreign equity securities may often be valued at fair value. The adviser generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment. The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.

Notes to Financial Statements (unaudited) – continued

Various inputs are used in determining the value of the fund’s assets or liabilities. These inputs are categorized into three broad levels. In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, an investment’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The fund’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Level 1 includes unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes unobservable inputs, which may include the adviser’s own assumptions in determining the fair value of investments. The following is a summary of the levels used as of February 29, 2020 in valuing the fund’s assets or liabilities:



Financial Instruments	Level 1			Level 2		Level 3		Total
Equity Securities		$3,310,781,829			$—		$—		$3,310,781,829
Mutual Funds		59,068,993			—		—		59,068,993
Total		$3,369,850,822			$—		$—		$3,369,850,822
Securities Sold Short		$(17,203,271	)		$—		$—		$(17,203,271	)

For further information regarding security characteristics, see the Portfolio of Investments.

Foreign Currency Translation– Purchases and sales of foreign investments, income, and expenses are converted into U.S. dollars based upon currency exchange rates prevailing on the respective dates of such transactions or on the reporting date for foreign denominated receivables and payables. Gains and losses attributable to foreign currency exchange rates on sales of securities are recorded for financial statement purposes as net realized gains and losses on investments. Gains and losses attributable to foreign exchange rate movements on receivables, payables, income and expenses are recorded for financial statement purposes as foreign currency transaction gains and losses. That portion of both realized and unrealized gains and losses on investments that results from fluctuations in foreign currency exchange rates is not separately disclosed.

Short Sales– The fund entered into short sales whereby it sells a security it does not own in anticipation of a decline in the value of that security. The fund will realize a gain if the security price decreases and a loss if the security price increases between the date of the short sale and the date on which the fund replaces the borrowed security. Losses from short sales can exceed the proceeds of the security sold; and they can also exceed the potential loss from an ordinary buy and sell transaction. The amount of any premium, dividends, or interest the fund may be required to pay in connection with a short sale will be recognized as a fund expense. During the six months ended February 29, 2020, this expense amounted to $423,285. The fund segregates cash or marketable securities in an amount that, when combined with the amount of proceeds from the short sale deposited with the broker, at least equals the current market value of the security sold short.

Notes to Financial Statements (unaudited) – continued

can be terminated at the discretion of either the lending agent or the fund and the related securities must be returned within the earlier of the standard trade settlement period for such securities or within three business days. The loans are collateralized by cash and/or U.S. Treasury and federal agency obligations in an amount typically at least equal to the market value of the securities loaned. On loans collateralized by cash, the cash collateral is invested in a money market fund. The market value of the loaned securities is determined at the close of business of the fund and any additional required collateral is delivered to the fund on the next business day. The lending agent provides the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income. At February 29, 2020, there were no securities on loan or collateral outstanding.

Indemnifications– Under the fund’s organizational documents, its officers and Trustees may be indemnified against certain liabilities and expenses arising out of the performance of their duties to the fund. Additionally, in the normal course of business, the fund enters into agreements with service providers that may contain indemnification clauses. The fund’s maximum exposure under these agreements is unknown as this would involve future claims that may be made against the fund that have not yet occurred.

Investment Transactions and Income– Investment transactions are recorded on the trade date. Dividends received in cash are recorded on theex-dividend date. Certain dividends from foreign securities will be recorded when the fund is informed of the dividend if such information is obtained subsequent to theex-dividend date. Dividend payments received in additional securities are recorded on theex-dividend date in an amount equal to the value of the security on such date.

The fund may receive proceeds from litigation settlements. Any proceeds received from litigation involving portfolio holdings are reflected in the Statement of Operations in realized gain/loss if the security has been disposed of by the fund or in unrealized gain/loss if the security is still held by the fund. Any other proceeds from litigation not related to portfolio holdings are reflected as other income in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

no provision for federal income tax is required. The fund’s federal tax returns, when filed, will remain subject to examination by the Internal Revenue Service for a three year period. Management has analyzed the fund’s tax positions taken on federal and state tax returns for all open tax years and does not believe that there are any uncertain tax positions that require recognition of a tax liability. Foreign taxes, if any, have been accrued by the fund in the accompanying financial statements in accordance with the applicable foreign tax law. Foreign income taxes may be withheld by certain countries in which the fund invests. Additionally, capital gains realized by the fund on securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.

Distributions to shareholders are recorded on theex-dividend date. Income and capital gain distributions are determined in accordance with income tax regulations, which may differ from U.S. generally accepted accounting principles. Certain capital accounts in the financial statements are periodically adjusted for permanent differences in order to reflect their tax character. These adjustments have no impact on net assets or net asset value per share. Temporary differences which arise from recognizing certain items of income, expense, gain or loss in different periods for financial statement and tax purposes will reverse at some time in the future.

Book/tax differences primarily relate to wash sale loss deferrals and treating a portion of the proceeds from redemptions as a distribution for tax purposes.

The tax character of distributions made during the current period will be determined at fiscal year end. The tax character of distributions declared to shareholders for the last fiscal year is as follows:



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$27,039,464
Long-term capital gains		172,760,670

Total distributions		$199,800,134

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$2,856,545,915
Gross appreciation	634,941,165

Gross depreciation	(121,636,258	)
Net unrealized appreciation (depreciation)	$513,304,907

As of 8/31/19

Undistributed ordinary income	21,523,258
Undistributed long-term capital gain	42,076,042
Other temporary differences	867,245
Net unrealized appreciation (depreciation)	584,605,909

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.

Notes to Financial Statements (unaudited) – continued

Multiple Classes of Shares of Beneficial Interest– The fund offers multiple classes of shares, which differ in their respective distribution and service fees. The fund’s income, realized and unrealized gain (loss), and common expenses are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B shares will convert to Class A shares approximately eight years after purchase. Class C shares will convert to Class A shares approximately ten years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$29,982,091		$105,866,198
Class B		475,008		2,489,868
Class C		2,151,200		5,804,466
Class I		11,488,721		25,883,573
Class R1		53,748		326,330
Class R2		241,357		1,217,794
Class R3		966,738		3,436,027
Class R4		613,572		2,469,308
Class R6		17,877,056		52,306,570
Total		$63,849,491		$199,800,134

(3) Transactions with Affiliates

Investment Adviser– The fund has an investment advisory agreement with MFS to provide overall investment management and related administrative services and facilities to the fund. The management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets:


Up to $500 million	0.65	%
In excess of $500 million and up to $2.5 billion	0.55	%
In excess of $2.5 billion and up to $5 billion	0.50	%
In excess of $5 billion and up to $10 billion	0.47	%
In excess of $10 billion	0.45	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $167,763, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.54% of the fund’s average daily net assets.

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $257,257 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Notes to Financial Statements (unaudited) – continued

The fund’s distribution plan provides that the fund will pay MFD for services provided by MFD and financial intermediaries in connection with the distribution and servicing of certain share classes. One component of the plan is a distribution fee paid to MFD and another component of the plan is a service fee paid to MFD. MFD may subsequently pay all, or a portion, of the distribution and/or service fees to financial intermediaries.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.24%		$1,979,788
Class B		0.75%		0.25%		1.00%		1.00%		135,816
Class C		0.75%		0.25%		1.00%		1.00%		526,158
Class R1		0.75%		0.25%		1.00%		1.00%		16,170
Class R2		0.25%		0.25%		0.50%		0.49%		36,687
Class R3		—		0.25%		0.25%		0.25%		64,603
Total Distribution and Service Fees										$2,759,222

(d)

In accordance with the distribution plan for certain classes, the fund pays distribution and/or service fees equal to these annual percentage rates of each class’s average daily net assets. The distribution and service fee rates disclosed by class represent the current rates in effect at the end of the reporting period. Any rate changes, if applicable, are detailed below.

(e)

Certain Class A shares are subject to a contingent deferred sales charge (CDSC) in the event of a shareholder redemption within 18 months of purchase. Class B shares are subject to a CDSC in the event of a shareholder redemption within six years of purchase. Class C shares are subject to a CDSC in the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the six months ended February 29, 2020, were as follows:



	Amount
Class A		$12,780
Class B		7,601
Class C		2,995

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $182,243, which equated to 0.0110% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended

Notes to Financial Statements (unaudited) – continued

February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $988,958.

Administrator– MFS provides certain financial, legal, shareholder communications, compliance, and other administrative services to the fund. Under an administrative services agreement, the fund reimburses MFS the costs incurred to provide these services. The fund is charged an annual fixed amount of $17,500 plus a fee based on average daily net assets. The administrative services fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.0131% of the fund’s average daily net assets.

Trustees’ and Officers’ Compensation– The fund pays compensation to independent Trustees in the form of a retainer, attendance fees, and additional compensation to Board and Committee chairpersons. The fund does not pay compensation directly to Trustees or officers of the fund who are also officers of the investment adviser, all of whom receive remuneration from MFS for their services to the fund. Certain officers and Trustees of the fund are officers or directors of MFS, MFD, and MFSC.

Prior to December 31, 2001, the fund had an unfunded defined benefit plan (“DB plan”) for independent Trustees. As of December 31, 2001, the Board took action to terminate the DB plan with respect to then-current and any future independent Trustees, such that the DB plan covers only certain of those former independent Trustees who retired on or before December 31, 2001. The DB plan resulted in a net decrease in pension expense of $487 and is included in “Independent Trustees’ compensation” in the Statement of Operations for the six months ended February 29, 2020. The liability for deferred retirement benefits payable to those former independent Trustees under the DB plan amounted to $8,222 at February 29, 2020, and is included in “Payable for independent Trustees’ compensation” in the Statement of Assets and Liabilities.

Other –The fund invests in the MFS Institutional Money Market Portfolio which is managed by MFS and seeks current income consistent with preservation of capital and liquidity. This money market fund does not pay a management fee to MFS but does incur investment and operating costs.

On October 25, 2019, MFS purchased 3,570 shares of Class R4 for an aggregate amount of $124,919.

The fund is permitted to engage in purchase and sale transactions with funds and accounts for which MFS serves as investment adviser orsub-adviser (“cross-trades”) pursuant to a policy adopted by the Board of Trustees. This policy has been designed to ensure that cross-trades conducted by the fund comply with Rule17a-7 under the Investment Company Act of 1940. During the six months ended February 29, 2020, the fund engaged in purchase transactions pursuant to this policy, which amounted to $494,891.

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $86,871, which is included in “Other” income in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short sales and short-term obligations, aggregated $1,050,435,918 and $753,965,967, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20				Year ended 8/31/19

	Shares		Amount		Shares		Amount
Shares sold
Class A		5,567,415		$190,419,973		9,634,178		$300,587,873
Class B		9,057		272,708		108,329		2,957,560
Class C		669,614		19,692,591		1,116,113		29,419,493
Class I		5,091,554		185,752,640		10,576,543		346,152,292
Class R1		13,023		383,890		19,278		514,159
Class R2		75,351		2,498,085		140,877		4,281,134
Class R3		477,072		16,335,249		558,827		17,349,962
Class R4		105,983		3,689,962		235,627		7,596,808
Class R6		6,387,798		235,197,031		8,080,095		268,741,520
		18,396,867		$654,242,129		30,469,867		$977,600,801

Shares issued in connection with acquisition of MFS Equity
Opportunities Fund
Class A		3,575,449		$118,383,117
Class B		246,884		7,102,850
Class C		1,200,588		34,084,698
Class I		1,634,666		57,523,902
Class R1		3,682		104,467
Class R2		15,173		489,189
Class R3		23,823		786,385
Class R4		22,752		760,839
Class R6		229,660		8,100,125
		6,952,677		$227,335,572

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares issued to shareholders in reinvestment of distributions
Class A		856,833			$28,952,375			3,617,902			$102,241,924
Class B		15,738			462,711			98,656			2,438,781
Class C		69,056			1,999,170			228,301			5,570,537
Class I		301,669			10,829,902			818,315			24,524,913
Class R1		1,854			53,748			13,385			326,330
Class R2		7,179			236,698			42,497			1,172,074
Class R3		28,695			966,738			121,888			3,436,027
Class R4		17,867			609,088			86,084			2,452,539
Class R6		467,693			16,822,916			1,640,473			49,246,989
		1,766,584			$60,933,346			6,667,501			$191,410,114

Shares reacquired
Class A		(3,783,624	)		$(129,913,811	)		(5,585,845	)		$(172,873,286	)
Class B		(164,608	)		(4,919,509	)		(294,676	)		(7,961,871	)
Class C		(418,108	)		(12,254,341	)		(647,045	)		(17,059,886	)
Class I		(3,605,757	)		(132,147,306	)		(4,654,776	)		(148,719,791	)
Class R1		(23,064	)		(674,834	)		(33,857	)		(870,193	)
Class R2		(83,489	)		(2,785,220	)		(215,066	)		(6,465,638	)
Class R3		(164,518	)		(5,635,174	)		(400,269	)		(12,423,690	)
Class R4		(110,297	)		(3,799,647	)		(233,321	)		(7,058,208	)
Class R6		(2,342,081	)		(86,509,390	)		(3,009,716	)		(100,053,397	)
		(10,695,546	)		$(378,639,232	)		(15,074,571	)		$(473,485,960	)

Net change
Class A		6,216,073			$207,841,654			7,666,235			$229,956,511
Class B		107,071			2,918,760			(87,691	)		(2,565,530	)
Class C		1,521,150			43,522,118			697,369			17,930,144
Class I		3,422,132			121,959,138			6,740,082			221,957,414
Class R1		(4,505	)		(132,729	)		(1,194	)		(29,704	)
Class R2		14,214			438,752			(31,692	)		(1,012,430	)
Class R3		365,072			12,453,198			280,446			8,362,299
Class R4		36,305			1,260,242			88,390			2,991,139
Class R6		4,743,070			173,610,682			6,710,852			217,935,112
		16,420,582			$563,871,815			22,062,797			$695,524,955

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

Notes to Financial Statements (unaudited) – continued

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $7,450 and $0, respectively, and are included in “Interest expense and fees” in the Statement of Operations.

(7) Investments in Affiliated Issuers

An affiliated issuer may be considered one in which the fund owns 5% or more of the outstanding voting securities, or a company which is under common control. For the purposes of this report, the following were affiliated issuers:



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)			Change in Unrealized Appreciation or Depreciation		Ending Value
MFS Institutional Money
Market Portfolio		$36,346,848		$374,600,160		$351,874,435		$(5,208	)		$1,628		$59,068,993

Affiliated Issuers										Dividend Income		Capital Gain Distributions
MFS Institutional Money Market Portfolio											$449,718		$—

(8) Acquisitions

At close of business on October 25, 2019, the MFS Core Equity Fund with net assets of approximately $2,981,074,655, acquired all of the assets and liabilities of MFS Equity Opportunities Fund. The purpose of the transaction was to provide shareholders of MFS Equity Opportunities Fund the opportunity to participate in a larger combined portfolio with a similar investment objective and similar investment policies and strategies. The acquisition was accomplished by atax-free exchange of approximately 6,952,677 shares of the fund (valued at approximately $227,335,572) for all of the assets and liabilities of MFS Equity Opportunities Fund. MFS Equity Opportunities Fund then distributed the shares of the fund that MFS Equity Opportunities Fund received from the fund to its shareholders. MFS Equity Opportunities Fund’s investments on that date were valued at approximately $227,592,285 with a cost basis of approximately $222,463,162. For financial reporting purposes, assets received and shares issued by the fund were recorded at fair value; however, the cost basis of the investments received from MFS Equity Opportunities Fund were carried forward to align ongoing reporting of the fund’s realized and unrealized gains and losses with amounts distributable to shareholders for tax purposes. Because the combined investment

Notes to Financial Statements (unaudited) – continued

portfolios have been managed as a single integrated portfolio since the acquisition was completed, it is not practicable to separate the amounts of revenue and earnings of MFS Equity Opportunities Fund that have been included in the fund’s Statement of Operations since October 25, 2019. No pro forma information is provided as it is not material to the combined fund results.

(9) Impacts of COVID-19

The pandemic related to the global spread of novel coronavirus disease (COVID-19), which was first detected in December 2019, has resulted in significant disruptions to global business activity and the global economy, as well as the economies of individual countries, the financial performance of individual companies and sectors, and the securities and commodities markets in general. This pandemic, the full effects of which are still unknown, has resulted in substantial market volatility and may have adversely impacted the prices and liquidity of the fund’s investments and the fund’s performance during the period February 29, 2020 through April 16, 2020, the date that these financial statements were issued.

PROXY VOTING POLICIES AND INFORMATION

MFS votes proxies on behalf of the fund pursuant to proxy voting policies and procedures that are available without charge, upon request, by calling1-800-225-2606, by visitingmfs.com/proxyvoting, or by visiting the SEC’s Web site athttp://www.sec.gov.

Information regarding how the fund voted proxies relating to portfolio securities during the most recent twelve-month period ended June 30 is available by August 31 of each year without charge by visitingmfs.com/proxyvoting, or by visiting the SEC’s Web site athttp://www.sec.gov.

QUARTERLY PORTFOLIO DISCLOSURE

The fund files a complete schedule of portfolio holdings with the SEC for the first and third quarters of each fiscal year as an exhibit to its reports onForm N-PORT. The fund’s Form N-PORT reports are available on the SEC’s website athttp://www.sec.gov.A shareholder can obtain the portfolio holdings report for the first and third quarters of the fund’s fiscal year atmfs.com/openendfunds by choosing the fund’s name and then selecting the “Resources” tab and clicking on “Prospectus and Reports”.

FURTHER INFORMATION

From time to time, MFS may post important information about the fund or the MFS funds on the MFS web site (mfs.com). This information is available athttps://www.mfs.com/en-us/what-we-do/announcements.html or atmfs.com/openendfunds by choosing the fund’s name.

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

The fund has entered into contractual arrangements with an investment adviser, administrator, distributor, shareholder servicing agent, 529 program manager (if applicable), and custodian who each provide services to the fund. Unless expressly stated otherwise, shareholders are not parties to, or intended beneficiaries of these contractual arrangements, and these contractual arrangements are not intended to create any shareholder right to enforce them against the service providers or to seek any remedy under them against the service providers, either directly or on behalf of the fund.

Under the Trust’s By-Laws and Declaration of Trust, any claims asserted against or on behalf of the MFS Funds, including claims against Trustees and Officers, must be brought in state and federal courts located within the Commonwealth of Massachusetts.

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

The fund produces financial reports every six months and updates its summary prospectus and prospectus annually. To avoid sending duplicate copies of materials to households, only one copy of the fund’s annual and semiannual report and summary prospectus may be mailed to shareholders having the same last name and residential address on the fund’s records. However, any shareholder may contact MFSC (please see back cover for address and telephone number) to request that copies of these reports and summary prospectuses be sent personally to that shareholder.

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1. Go to mfs.com.

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If you own your MFS fund shares through a financial institution or a retirement plan, MFS® TALK, MFS® Access, or eDelivery may not be available to you.

CONTACT

WEB SITE

mfs.com

MFS TALK

1-800-637-8255

24 hours a day

ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

Financial advisors

1-800-343-2829

Retirement plan services

1-800-637-1255

MAILING ADDRESS

MFS Service Center, Inc.

P.O. Box 219341

Kansas City, MO 64121-9341

OVERNIGHT MAIL

MFS Service Center, Inc.

Suite 219341

430 W 7th Street

Kansas City, MO 64105-1407

Semiannual Report

February 29, 2020

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MFS® Low Volatility Global Equity Fund

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LVO-SEM

MFS® Low Volatility Global Equity Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			4
Portfolio of investments			6
Statement of assets and liabilities			11
Statement of operations			13
Statements of changes in net assets			14
Financial highlights			15
Notes to financial statements			24
Proxy voting policies and information			35
Quarterly portfolio disclosure			35
Further information			35
Information about fund contracts and legal claims			35
Provision of financial reports and summary prospectuses			35


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Roche Holding AG			3.9%
Taiwan Semiconductor Manufacturing Co. Ltd., ADR			2.9%
Johnson & Johnson			2.7%
Adobe Systems, Inc.			2.7%
STORE Capital Corp., REIT			2.3%
PepsiCo, Inc.			2.1%
Lockheed Martin Corp.			2.1%
Terumo Corp.			2.1%
Starbucks Corp.			2.1%
ABC-MART, Inc.			2.0%


GICS equity sectors (g)
Health Care			16.0%
Consumer Staples			14.9%
Information Technology			13.5%
Consumer Discretionary			11.0%
Financials			11.0%
Communication Services			10.3%
Real Estate			8.3%
Utilities			8.1%
Industrials			6.1%
Materials			2.5%
Energy			2.1%

Issuer country weightings (x)
United States			42.5%
Japan			12.6%
Canada			8.9%
Switzerland			7.4%
United Kingdom			3.8%
Hong Kong			3.6%
Germany			3.3%
Taiwan			2.9%
Australia			2.1%
Other Countries			12.9%

Portfolio Composition – continued


Currency exposure weightings (y)
United States Dollar			51.4%
Japanese Yen			12.6%
Swiss Franc			7.4%
Euro			5.7%
British Pound Sterling			3.8%
Hong Kong Dollar			3.0%
Taiwan Dollar			2.9%
Australian Dollar			2.1%
Indian Rupee			1.7%
Other Currencies			9.4%

(g)	The Global Industry Classification Standard (GICS®) was developed by and/or is the exclusive property of MSCI, Inc. and S&P Global Market Intelligence Inc. (“S&P Global Market Intelligence”). GICS is a service mark of MSCI and S&P Global Market Intelligence and has been licensed for use by MFS.

(x)	Represents the portfolio’s exposure to issuer countries as a percentage of a portfolio’s net assets. For purposes of this presentation, United States includes Cash & Cash Equivalents.

(y)	Represents the portfolio’s exposure to a particular currency as a percentage of a portfolio’s net assets. For purposes of this presentation, United States Dollar includes Cash & Cash Equivalents.

From time to time Cash & Cash Equivalents may be negative due to timing of cash receipts and disbursements.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		1.00%		$1,000.00		$982.91		$4.93
A	Hypothetical (h)		1.00%		$1,000.00		$1,019.89		$5.02
B	Actual		1.75%		$1,000.00		$979.53		$8.61
B	Hypothetical (h)		1.75%		$1,000.00		$1,016.16		$8.77
C	Actual		1.75%		$1,000.00		$979.67		$8.61
C	Hypothetical (h)		1.75%		$1,000.00		$1,016.16		$8.77
I	Actual		0.75%		$1,000.00		$984.83		$3.70
I	Hypothetical (h)		0.75%		$1,000.00		$1,021.13		$3.77
R1	Actual		1.75%		$1,000.00		$978.97		$8.61
R1	Hypothetical (h)		1.75%		$1,000.00		$1,016.16		$8.77
R2	Actual		1.25%		$1,000.00		$981.64		$6.16
R2	Hypothetical (h)		1.25%		$1,000.00		$1,018.65		$6.27
R3	Actual		1.00%		$1,000.00		$982.88		$4.93
R3	Hypothetical (h)		1.00%		$1,000.00		$1,019.89		$5.02
R4	Actual		0.75%		$1,000.00		$984.84		$3.70
R4	Hypothetical (h)		0.75%		$1,000.00		$1,021.13		$3.77
R6	Actual		0.68%		$1,000.00		$984.59		$3.36
R6	Hypothetical (h)		0.68%		$1,000.00		$1,021.48		$3.42

(h)	5% class return per year before expenses.

(p)

Notes to Expense Table

Expense ratios include approximately 0.01% of interest expenses that are outside of the expense limitation arrangement (See Note 3 of the Notes to Financial Statements).

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 103.8%
Aerospace - 2.6%
Leidos Holdings, Inc.		11,800	$	1,211,270
Lockheed Martin Corp.		13,070		4,834,201

			$	6,045,471
Airlines - 0.4%
Malaysia Airports Holdings Berhad		606,800	$	952,134

Automotive - 0.8%
USS Co. Ltd.		113,000	$	1,781,145

Broadcasting - 0.5%
Publicis Groupe S.A.		32,415	$	1,253,886

Business Services - 4.1%
Auto Trader Group PLC		190,556	$	1,285,888
CGI, Inc. (a)		22,300		1,570,143
Fiserv, Inc. (a)		25,291		2,765,824
Infosys Technologies Ltd., ADR		382,020		3,846,941

			$	9,468,796
Cable TV - 0.4%
Comcast Corp., “A”		22,191	$	897,182

Computer Software - 2.7%
Adobe Systems, Inc. (a)		17,633	$	6,085,501

Computer Software - Systems - 2.3%
Fujitsu Ltd.		12,800	$	1,350,833
Hitachi Ltd.		34,000		1,140,461
NICE Systems Ltd., ADR (a)		16,573		2,715,155

			$	5,206,449
Construction - 1.9%
AvalonBay Communities, Inc., REIT		16,247	$	3,258,985
Rinnai Corp.		17,500		1,183,399

			$	4,442,384
Consumer Products - 2.8%
Kimberly-Clark Corp.		17,724	$	2,325,212
L’Oréal		4,154		1,117,200

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Consumer Products - continued
Procter & Gamble Co.		26,432	$	2,992,895

			$	6,435,307
Electronics - 4.5%
Kyocera Corp.		56,100	$	3,516,099
Taiwan Semiconductor Manufacturing Co. Ltd., ADR		124,491		6,702,595

			$	10,218,694
Energy - Integrated - 1.1%
Eni S.p.A.		61,845	$	765,610
Royal Dutch Shell PLC, “B”		79,497		1,726,344

			$	2,491,954
Entertainment - 0.4%
CTS Eventim AG		18,565	$	981,933

Food & Beverages - 7.8%
General Mills, Inc.		62,094	$	3,042,606
Mondelez International, Inc.		40,161		2,120,501
Mowi A.S.A.		102,530		2,173,066
Nestle S.A.		40,686		4,215,353
PepsiCo, Inc.		37,346		4,930,792
Toyo Suisan Kaisha Ltd.		37,300		1,494,325

			$	17,976,643
Food & Drug Stores - 3.8%
Dairy Farm International Holdings Ltd.		281,900	$	1,353,120
Lawson, Inc. (l)		18,900		1,015,005
Seven & I Holdings Co. Ltd. (l)		68,200		2,328,869
Tesco PLC		310,353		916,716
Wesfarmers Ltd.		120,933		3,157,335

			$	8,771,045
Gaming & Lodging - 1.9%
Crown Resorts Ltd.		258,067	$	1,723,053
Genting Berhad		2,310,300		2,713,164

			$	4,436,217
Health Maintenance Organizations - 1.0%
Cigna Corp.		12,185	$	2,229,124

Insurance - 6.0%
Beazley PLC		253,172	$	1,742,244
Everest Re Group Ltd.		14,682		3,639,374

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued

Insurance - continued
MetLife, Inc.		85,978	$	3,672,980
Reinsurance Group of America, Inc.		12,600		1,537,578
Samsung Fire & Marine Insurance Co. Ltd.		7,658		1,248,484
Zurich Insurance Group AG		5,172		2,012,780

			$	13,853,440
Internet - 0.9%
Alphabet, Inc., “A” (a)		1,610	$	2,156,192

Machinery & Tools - 0.8%
AGCO Corp.		15,164	$	916,361
Doosan Bobcat, Inc.		38,139		902,949

			$	1,819,310
Major Banks - 2.1%
Bank of Nova Scotia		20,354	$	1,065,532
PNC Financial Services Group, Inc.		12,914		1,632,329
Royal Bank of Canada		27,853		2,074,213

			$	4,772,074
Medical & Health Technology & Services - 0.4%
McKesson Corp.		6,717	$	939,440

Medical Equipment - 3.0%
EssilorLuxottica		16,257	$	2,240,726
Terumo Corp.		147,900		4,738,053

			$	6,978,779
Natural Gas - Pipeline - 1.0%
Enbridge, Inc.		63,384	$	2,372,463

Other Banks & Diversified Financials - 2.9%
Credicorp Ltd.		10,219	$	1,852,398
DBS Group Holdings Ltd.		52,800		922,016
Komercni Banka A.S.		40,521		1,243,843
U.S. Bancorp		57,098		2,651,631

			$	6,669,888
Pharmaceuticals - 12.5%
Eli Lilly & Co.		23,246	$	2,932,018
Johnson & Johnson		46,819		6,296,219
Merck & Co., Inc.		44,190		3,383,186
Novartis AG		21,607		1,813,891
Novo Nordisk A.S., “B”		60,671		3,605,888

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Pharmaceuticals - continued
Pfizer, Inc.		55,669	$	1,860,458
Roche Holding AG		27,329		8,907,737

			$	28,799,397
Pollution Control - 2.0%
Waste Connections, Inc.		47,167	$	4,551,144

Precious Metals & Minerals - 1.3%
Franco-Nevada Corp.		27,444	$	2,946,307

Railroad & Shipping - 0.8%
Canadian National Railway Co.		21,924	$	1,861,567

Real Estate - 6.9%
Grand City Properties S.A.		165,975	$	3,890,636
Life Storage, Inc., REIT		17,403		1,877,958
Public Storage, Inc., REIT		7,249		1,515,911
STORE Capital Corp., REIT		157,417		5,172,722
Sun Communities, Inc., REIT		21,784		3,330,338

			$	15,787,565
Restaurants - 4.1%
McDonald’s Corp.		16,867	$	3,275,065
Starbucks Corp.		60,067		4,711,055
U.S. Foods Holding Corp. (a)		41,826		1,407,027

			$	9,393,147
Specialty Chemicals - 1.2%
Symrise AG		27,616	$	2,689,770

Specialty Stores - 2.0%
ABC-MART, Inc.		79,600	$	4,585,910

Telecommunications - Wireless - 3.3%
Advanced Info Service Public Co. Ltd.		213,000	$	1,356,774
KDDI Corp.		142,400		4,024,279
Vodafone Group PLC		1,197,435		2,091,225

			$	7,472,278
Telephone Services - 4.2%
HKT Trust and HKT Ltd.		2,154,000	$	3,230,084
TELUS Corp.		107,401		3,895,434
Verizon Communications, Inc.		46,326		2,509,016

			$	9,634,534

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Tobacco - 1.3%
British American Tobacco PLC		26,230	$	1,042,375
Japan Tobacco, Inc.		92,500		1,834,412

			$	2,876,787
Utilities - Electric Power - 8.1%
American Electric Power Co., Inc.		29,449	$	2,628,618
Avangrid, Inc.		33,205		1,649,956
CEZ A.S. (Czech Republic)		36,304		695,772
CLP Holdings Ltd.		351,000		3,698,441
Duke Energy Corp.		11,184		1,025,573
Evergy, Inc.		40,996		2,679,089
WEC Energy Group, Inc.		33,494		3,092,501
Xcel Energy, Inc.		49,453		3,081,911

			$	18,551,861
Total Common Stocks (Identified Cost, $210,698,290)			$	238,385,718

Investment Companies (h) - 0.4%
Money Market Funds - 0.4%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $953,485)		953,485	$	953,580

Collateral for Securities Loaned - 0.0%
State Street Navigator Securities Lending Government Money Market Portfolio, 1.61% (j) (Identified Cost, $22,995)		22,995	$	22,995

Other Assets, Less Liabilities - (4.2)%			(9,750,464)
Net Assets - 100.0%			$	229,611,829

(a)	Non-income producing security.

(h)

(j)	The rate quoted is the annualizedseven-day yield of the fund at period end.

(l)	A portion of this security is on loan. See Note 2 for additional information.

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

ADR

American Depositary Receipt

REIT

Real Estate Investment Trust

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value, including $2,835,202 of securities on loan (identified cost, $210,721,285)			$238,408,713
Investments in affiliated issuers, at value (identified cost, $953,485)			953,580
Cash			23,479
Receivables for
Fund shares sold			1,171,942
Interest and dividends			869,459
Other assets			976
Total assets			$241,428,149
Liabilities
Payables for
Investments purchased			$326,657
Fund shares reacquired			11,361,592
Collateral for securities loaned, at value (c)			22,995
Payable to affiliates
Investment adviser			6,944
Administrative services fee			355
Shareholder servicing costs			53,329
Distribution and service fees			701
Payable for independent Trustees’ compensation			776
Deferred country tax expense payable			5,186
Accrued expenses and other liabilities			37,785
Total liabilities			$11,816,320
Net assets			$229,611,829
Net assets consist of
Paid-in capital			$204,803,371
Total distributable earnings (loss)			24,808,458
Net assets			$229,611,829
Shares of beneficial interest outstanding			17,071,870

(c)	Non-cash collateral is not included.

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$23,317,143		1,733,353		$13.45
Class B		394,971		29,569		13.36
Class C		3,035,826		227,594		13.34
Class I		106,847,306		7,939,668		13.46
Class R1		99,513		7,419		13.41
Class R2		159,599		11,864		13.45
Class R3		74,456		5,528		13.47
Class R4		70,651		5,249		13.46
Class R6		95,612,364		7,111,626		13.44

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $14.27 [100 / 94.25 x $13.45]. On sales of $50,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$2,581,833
Dividends from affiliated issuers	12,281
Other	5,036
Income on securities loaned	331
Foreign taxes withheld	(126,843	)
Total investment income	$2,472,638
Expenses
Management fee	$643,059
Distribution and service fees	46,866
Shareholder servicing costs	67,833
Administrative services fee	20,488
Independent Trustees’ compensation	4,823
Custodian fee	37,063
Shareholder communications	14,383
Audit and tax fees	28,131
Legal fees	1,069
Registration fees	65,596
Miscellaneous	30,564
Total expenses	$959,875
Reduction of expenses by investment adviser and distributor	(67,479	)
Net expenses	$892,396
Net investment income (loss)	$1,580,242

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers (net of $1,386 country tax)	$326,089
Affiliated issuers	476
Foreign currency	(3,517	)
Net realized gain (loss)	$323,048
Change in unrealized appreciation or depreciation
Unaffiliated issuers (net of $31,442 decrease in deferred country tax)	$(7,318,980	)
Affiliated issuers	50
Translation of assets and liabilities in foreign currencies	2,119
Net unrealized gain (loss)	$(7,316,811	)
Net realized and unrealized gain (loss)	$(6,993,763	)
Change in net assets from operations	$(5,413,521	)

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$1,580,242			$4,684,916
Net realized gain (loss)		323,048			1,976,712
Net unrealized gain (loss)		(7,316,811	)		10,762,414
Change in net assets from operations		$(5,413,521	)		$17,424,042
Total distributions to shareholders		$(4,251,075	)		$(10,518,952	)
Change in net assets from fund share transactions		$19,886,224			$17,311,467
Total change in net assets		$10,221,628			$24,216,557

Net assets
At beginning of period		219,390,201			195,173,644
At end of period		$229,611,829			$219,390,201

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.92			$13.73			$12.82			$11.87			$10.75			$10.92

Income (loss) from investment operations
Net investment income (loss) (d)		$0.08			$0.25			$0.23			$0.19			$0.18			$0.19
Net realized and unrealized gain (loss)		(0.31	)		0.56			0.92			0.91			1.11			(0.22	)
Total from investment operations		$(0.23	)		$0.81			$1.15			$1.10			$1.29			$(0.03	)

Less distributions declared to shareholders
From net investment income		$(0.15	)		$(0.23	)		$(0.24	)		$(0.15	)		$(0.17	)		$(0.12	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.24	)		$(0.62	)		$(0.24	)		$(0.15	)		$(0.17	)		$(0.14	)
Net asset value, end of period (x)		$13.45			$13.92			$13.73			$12.82			$11.87			$10.75
Total return (%) (r)(s)(t)(x)		(1.71	)(n)		6.38			9.09			9.36			12.12			(0.36	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.06	(a)		1.05			1.06			1.23			1.51			1.88
Expenses after expense reductions (f)		1.00	(a)		0.98			0.97			1.17			1.19			1.23
Net investment income (loss)		1.11	(a)(l)		1.86			1.75			1.55			1.56			1.65
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$23,317			$19,981			$9,102			$9,215			$7,473			$3,981

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.82			$13.63			$12.73			$11.79			$10.70			$10.91

Income (loss) from investment operations
Net investment income (loss) (d)		$0.03			$0.14			$0.13			$0.09			$0.07			$0.08
Net realized and unrealized gain (loss)		(0.30	)		0.57			0.91			0.91			1.12			(0.20	)
Total from investment operations		$(0.27	)		$0.71			$1.04			$1.00			$1.19			$(0.12	)

Less distributions declared to shareholders
From net investment income		$(0.10	)		$(0.13	)		$(0.14	)		$(0.06	)		$(0.10	)		$(0.07	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.19	)		$(0.52	)		$(0.14	)		$(0.06	)		$(0.10	)		$(0.09	)
Net asset value, end of period (x)		$13.36			$13.82			$13.63			$12.73			$11.79			$10.70
Total return (%) (r)(s)(t)(x)		(2.05	)(n)		5.60			8.25			8.48			11.16			(1.16	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.81	(a)		1.79			1.81			1.98			2.33			2.68
Expenses after expense reductions (f)		1.75	(a)		1.74			1.74			1.96			1.98			2.01
Net investment income (loss)		0.35	(a)(l)		1.03			1.02			0.73			0.65			0.74
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$395			$410			$380			$350			$341			$446

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.80			$13.62			$12.71			$11.78			$10.69			$10.91

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.14			$0.13			$0.09			$0.08			$0.10
Net realized and unrealized gain (loss)		(0.29	)		0.57			0.92			0.91			1.11			(0.23	)
Total from investment operations		$(0.27	)		$0.71			$1.05			$1.00			$1.19			$(0.13	)

Less distributions declared to shareholders
From net investment income		$(0.10	)		$(0.14	)		$(0.14	)		$(0.07	)		$(0.10	)		$(0.07	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.19	)		$(0.53	)		$(0.14	)		$(0.07	)		$(0.10	)		$(0.09	)
Net asset value, end of period (x)		$13.34			$13.80			$13.62			$12.71			$11.78			$10.69
Total return (%) (r)(s)(t)(x)		(2.03	)(n)		5.57			8.28			8.49			11.22			(1.23	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.81	(a)		1.80			1.81			1.98			2.23			2.66
Expenses after expense reductions (f)		1.75	(a)		1.74			1.74			1.96			1.99			2.00
Net investment income (loss)		0.35	(a)(l)		1.02			1.01			0.76			0.74			0.89
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$3,036			$2,876			$1,773			$1,924			$1,554			$453

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.92			$13.73			$12.82			$11.87			$10.76			$10.93

Income (loss) from investment operations
Net investment income (loss) (d)		$0.10			$0.28			$0.27			$0.23			$0.21			$0.24
Net realized and unrealized gain (loss)		(0.30	)		0.56			0.91			0.90			1.10			(0.25	)
Total from investment operations		$(0.20	)		$0.84			$1.18			$1.13			$1.31			$(0.01	)

Less distributions declared to shareholders
From net investment income		$(0.17	)		$(0.26	)		$(0.27	)		$(0.18	)		$(0.20	)		$(0.14	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.26	)		$(0.65	)		$(0.27	)		$(0.18	)		$(0.20	)		$(0.16	)
Net asset value, end of period (x)		$13.46			$13.92			$13.73			$12.82			$11.87			$10.76
Total return (%) (r)(s)(t)(x)		(1.52	)(n)		6.61			9.34			9.59			12.34			(0.18	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.81	(a)		0.79			0.81			0.94			1.17			1.63
Expenses after expense reductions (f)		0.75	(a)		0.74			0.74			0.90			0.98			1.00
Net investment income (loss)		1.36	(a)(l)		2.09			2.03			1.87			1.86			2.10
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$106,847			$118,907			$114,259			$97,952			$10,669			$2,685

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.88			$13.69			$12.78			$11.84			$10.70			$10.91

Income (loss) from investment operations
Net investment income (loss) (d)		$0.03			$0.14			$0.14			$0.09			$0.08			$0.07
Net realized and unrealized gain (loss)		(0.31	)		0.58			0.91			0.91			1.12			(0.19	)
Total from investment operations		$(0.28	)		$0.72			$1.05			$1.00			$1.20			$(0.12	)

Less distributions declared to shareholders
From net investment income		$(0.10	)		$(0.14	)		$(0.14	)		$(0.06	)		$(0.06	)		$(0.07	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.19	)		$(0.53	)		$(0.14	)		$(0.06	)		$(0.06	)		$(0.09	)
Net asset value, end of period (x)		$13.41			$13.88			$13.69			$12.78			$11.84			$10.70
Total return (%) (r)(s)(t)(x)		(2.10	)(n)		5.61			8.29			8.47			11.24			(1.22	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.81	(a)		1.79			1.81			1.98			2.31			2.69
Expenses after expense reductions (f)		1.75	(a)		1.74			1.74			1.96			1.99			2.01
Net investment income (loss)		0.36	(a)(l)		1.03			1.03			0.75			0.69			0.66
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$100			$96			$74			$68			$56			$108

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.92			$13.73			$12.81			$11.87			$10.74			$10.92

Income (loss) from investment operations
Net investment income (loss) (d)		$0.05			$0.21			$0.20			$0.15			$0.13			$0.13
Net realized and unrealized gain (loss)		(0.29	)		0.57			0.92			0.90			1.13			(0.20	)
Total from investment operations		$(0.24	)		$0.78			$1.12			$1.05			$1.26			$(0.07	)

Less distributions declared to shareholders
From net investment income		$(0.14	)		$(0.20	)		$(0.20	)		$(0.11	)		$(0.13	)		$(0.09	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.23	)		$(0.59	)		$(0.20	)		$(0.11	)		$(0.13	)		$(0.11	)
Net asset value, end of period (x)		$13.45			$13.92			$13.73			$12.81			$11.87			$10.74
Total return (%) (r)(s)(t)(x)		(1.84	)(n)		6.09			8.87			8.94			11.83			(0.71	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.31	(a)		1.29			1.31			1.49			1.79			2.19
Expenses after expense reductions (f)		1.25	(a)		1.24			1.24			1.47			1.49			1.51
Net investment income (loss)		0.74	(a)(l)		1.53			1.52			1.24			1.20			1.16
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$160			$75			$66			$61			$72			$112

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.94			$13.74			$12.82			$11.88			$10.76			$10.92

Income (loss) from investment operations
Net investment income (loss) (d)		$0.08			$0.24			$0.22			$0.19			$0.16			$0.16
Net realized and unrealized gain (loss)		(0.31	)		0.58			0.93			0.90			1.12			(0.19	)
Total from investment operations		$(0.23	)		$0.82			$1.15			$1.09			$1.28			$(0.03	)

Less distributions declared to shareholders
From net investment income		$(0.15	)		$(0.23	)		$(0.23	)		$(0.15	)		$(0.16	)		$(0.11	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.24	)		$(0.62	)		$(0.23	)		$(0.15	)		$(0.16	)		$(0.13	)
Net asset value, end of period (x)		$13.47			$13.94			$13.74			$12.82			$11.88			$10.76
Total return (%) (r)(s)(t)(x)		(1.71	)(n)		6.42			9.11			9.24			12.05			(0.34	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.06	(a)		1.04			1.05			1.21			1.56			1.94
Expenses after expense reductions (f)		1.00	(a)		0.99			0.99			1.18			1.24			1.26
Net investment income (loss)		1.11	(a)(l)		1.78			1.69			1.55			1.44			1.41
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$74			$71			$67			$151			$56			$110

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.92			$13.73			$12.82			$11.87			$10.76			$10.93

Income (loss) from investment operations
Net investment income (loss) (d)		$0.10			$0.27			$0.27			$0.21			$0.19			$0.19
Net realized and unrealized gain (loss)		(0.30	)		0.57			0.91			0.92			1.12			(0.20	)
Total from investment operations		$(0.20	)		$0.84			$1.18			$1.13			$1.31			$(0.01	)

Less distributions declared to shareholders
From net investment income		$(0.17	)		$(0.26	)		$(0.27	)		$(0.18	)		$(0.20	)		$(0.14	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.26	)		$(0.65	)		$(0.27	)		$(0.18	)		$(0.20	)		$(0.16	)
Net asset value, end of period (x)		$13.46			$13.92			$13.73			$12.82			$11.87			$10.76
Total return (%) (r)(s)(t)(x)		(1.52	)(n)		6.61			9.34			9.58			12.32			(0.18	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.81	(a)		0.79			0.81			0.98			1.31			1.69
Expenses after expense reductions (f)		0.75	(a)		0.74			0.74			0.96			0.99			1.02
Net investment income (loss)		1.35	(a)(l)		2.03			2.02			1.74			1.69			1.66
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$71			$72			$67			$62			$56			$110

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$13.91			$13.72			$12.81			$11.86			$10.76			$10.92

Income (loss) from investment operations
Net investment income (loss) (d)		$0.10			$0.28			$0.27			$0.21			$0.20			$0.20
Net realized and unrealized gain (loss)		(0.30	)		0.57			0.92			0.92			1.11			(0.20	)
Total from investment operations		$(0.20	)		$0.85			$1.19			$1.13			$1.31			$0.00

Less distributions declared to shareholders
From net investment income		$(0.18	)		$(0.27	)		$(0.28	)		$(0.18	)		$(0.21	)		$(0.14	)
From net realized gain		(0.09	)		(0.39	)		—			—			—			(0.02	)
Total distributions declared to shareholders		$(0.27	)		$(0.66	)		$(0.28	)		$(0.18	)		$(0.21	)		$(0.16	)
Net asset value, end of period (x)		$13.44			$13.91			$13.72			$12.81			$11.86			$10.76
Total return (%) (r)(s)(t)(x)		(1.54	)(n)		6.68			9.42			9.63			12.37			(0.09	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.73	(a)		0.72			0.74			0.94			1.21			1.63
Expenses after expense reductions (f)		0.68	(a)		0.67			0.67			0.92			0.93			0.97
Net investment income (loss)		1.44	(a)(l)		2.11			2.08			1.77			1.76			1.79
Portfolio turnover		8	(n)		65			41			24			28			61
Net assets at end of period (000 omitted)		$95,612			$76,901			$69,385			$68,569			$45,799			$27,802

(a)	Annualized.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(l)	Recognition of net investment income by the fund may be affected by the timing of the declaration of dividends by companies in which the fund invests and the actual annual net investment income ratio may differ.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Low Volatility Global Equity Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

General– The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued. The fund invests in foreign securities, including securities of emerging market issuers. Investments in foreign securities are vulnerable to the effects of changes in the relative values of the local currency and the U.S. dollar and to the effects of changes in each country’s market, economic, industrial, political, regulatory, geopolitical, and other conditions. Investments in emerging markets can involve additional and greater risks than the risks associated with investments in developed foreign markets. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, and greater political, social, and economic instability than developed markets.

Notes to Financial Statements (unaudited) – continued

setoff may be restricted or prohibited by the bankruptcy or insolvency laws of the particular jurisdiction to which a specific master netting agreement counterparty is subject. Balance sheet offsetting disclosures, to the extent applicable to the fund, have been included in the fund’s Significant Accounting Policies note under the captions for each of the fund’sin-scope financial instruments and transactions.

Investment Valuations–Equity securities, including restricted equity securities, are generally valued at the last sale or official closing price on their primary market or exchange as provided by a third-party pricing service. Equity securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

Notes to Financial Statements (unaudited) – continued

and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.



Financial Instruments	Level 1		Level 2		Level 3		Total
Equity Securities:
United States		$106,268,599		$—		$—		$106,268,599
Japan		—		28,992,790		—		28,992,790
Canada		20,336,803		—		—		20,336,803
Switzerland		—		16,949,761		—		16,949,761
United Kingdom		—		8,804,792		—		8,804,792
Hong Kong		1,353,120		6,928,525		—		8,281,645
Germany		—		7,562,339		—		7,562,339
Taiwan		6,702,595		—		—		6,702,595
Australia		—		4,880,388		—		4,880,388
Other Countries		13,732,916		15,873,090		—		29,606,006
Mutual Funds		976,575		—		—		976,575
Total		$149,370,608		$89,991,685		$—		$239,362,293

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

Security Loans– Under its Securities Lending Agency Agreement with the fund, State Street Bank and Trust Company, as lending agent, loans the securities of the fund to certain qualified institutions (the “Borrowers”) approved by the fund. Security loans can be terminated at the discretion of either the lending agent or the fund and the related securities must be returned within the earlier of the standard trade settlement period for such securities or within three business days. The loans are collateralized by cash and/or U.S. Treasury and federal agency obligations in an amount typically at least equal to the market value of the securities loaned. On loans collateralized by cash, the cash collateral is invested in a money market fund. The market value of the loaned securities is determined at the close of business of the fund and any additional required collateral is delivered to the fund on the next business day. The lending agent provides the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. At period end, the fund had investment securities on loan, all of which were classified as equity securities in the fund’s Portfolio of Investments, with a fair value of $2,835,202. The fair value of the fund’s investment securities on loan and a related liability of $22,995 for cash collateral received on securities loaned are both presented gross in the Statement of Assets and Liabilities. Additionally, these loans were collateralized by U.S. Treasury Obligations of $2,903,682 held by the lending agent. The collateral on securities loaned exceeded the value of securities on loan at period end. The liability for cash collateral for securities loaned is carried at fair value, which is categorized as level 2 within the fair value hierarchy. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income.

Notes to Financial Statements (unaudited) – continued

Tax Matters and Distributions– The fund intends to qualify as a regulated investment company, as defined under Subchapter M of the Internal Revenue Code, and to distribute all of its taxable income, including realized capital gains. As a result, no provision for federal income tax is required. The fund’s federal tax returns, when filed, will remain subject to examination by the Internal Revenue Service for a three year period. Management has analyzed the fund’s tax positions taken on federal and state tax returns for all open tax years and does not believe that there are any uncertain tax positions that require recognition of a tax liability. Foreign taxes, if any, have been accrued by the fund in the accompanying financial statements in accordance with the applicable foreign tax law. Foreign income taxes may be withheld by certain countries in which the fund invests. Additionally, capital gains realized by the fund on securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.

Book/tax differences primarily relate to passive foreign investment companies and wash sale loss deferrals.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$4,465,803
Long-term capital gains		6,053,149

Total distributions		$10,518,952

Notes to Financial Statements (unaudited) – continued

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$214,380,924
Gross appreciation	33,696,909

Gross depreciation	(8,715,540	)
Net unrealized appreciation (depreciation)	$24,981,369

As of 8/31/19

Undistributed ordinary income	1,949,792
Undistributed long-term capital gain	244,641
Other temporary differences	(70,923	)
Net unrealized appreciation (depreciation)	32,349,544

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$383,341		$549,580
Class B		5,599		14,039
Class C		42,211		77,581
Class I		2,168,954		6,406,191
Class R1		1,372		2,931
Class R2		2,280		2,854
Class R3		1,317		3,034
Class R4		1,365		3,226
Class R6		1,644,636		3,459,516
Total		$4,251,075		$10,518,952

(3) Transactions with Affiliates


Up to $1 billion	0.55	%
In excess of $1 billion and up to $2.5 billion	0.525	%
In excess of $2.5 billion	0.50	%

Notes to Financial Statements (unaudited) – continued

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $11,866, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.54% of the fund’s average daily net assets.

The investment adviser has agreed in writing to pay a portion of the fund’s total annual operating expenses, excluding interest, taxes, extraordinary expenses, brokerage and transaction costs, and investment-related expenses, such that total fund operating expenses do not exceed the following rates annually of each class’s average daily net assets:


Classes

A	B		C		I		R1		R2		R3		R4		R6
0.99%		1.74%		1.74%		0.74%		1.74%		1.24%		0.99%		0.74%		0.68%

This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue at least until December 31, 2020. For the six months ended February 29, 2020, this reduction amounted to $55,172, which is included in the reduction of total expenses in the Statement of Operations.

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $5,873 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.25%		$28,112
Class B		0.75%		0.25%		1.00%		1.00%		2,105
Class C		0.75%		0.25%		1.00%		1.00%		15,669
Class R1		0.75%		0.25%		1.00%		1.00%		509
Class R2		0.25%		0.25%		0.50%		0.50%		376
Class R3		—		0.25%		0.25%		0.25%		95
Total Distribution and Service Fees										$46,866

(d)

Notes to Financial Statements (unaudited) – continued

(e)



	Amount
Class A		$56
Class B		—
Class C		12

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $6,549, which equated to 0.0056% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $61,284.

Notes to Financial Statements (unaudited) – continued

At February 29, 2020, MFS held approximately 68% of the outstanding shares of Class R1, 94% of the outstanding shares of Class R3, and 100% of the outstanding shares of Class R4, respectively.

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $4,833, which is included in “Other” income in the Statement of Operations.

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short-term obligations, aggregated $46,034,693 and $18,340,368, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20				Year ended 8/31/19

	Shares		Amount		Shares		Amount
Shares sold
Class A		544,535		$7,840,801		1,041,729		$13,809,908
Class B		—		—		3,234		41,580
Class C		29,290		414,242		131,925		1,728,080
Class I		2,141,589		30,772,699		8,478,173		112,927,999
Class R1		383		5,497		1,336		18,304
Class R2		6,293		88,578		358		4,947
Class R3		338		4,863		—		—
Class R6		1,647,990		23,696,065		1,744,896		23,529,647
		4,370,418		$62,822,745		11,401,651		$152,060,465

Shares issued to shareholders in reinvestment of distributions
Class A		26,713		$383,172		42,848		$548,615
Class B		392		5,599		1,114		14,039
Class C		2,909		41,484		6,003		75,592
Class I		128,329		1,838,070		476,060		6,073,699
Class R1		96		1,372		231		2,931
Class R2		158		2,280		224		2,854
Class R3		92		1,317		238		3,033
Class R4		95		1,365		252		3,226
Class R6		110,203		1,578,067		261,566		3,338,647
		268,987		$3,852,726		788,536		$10,062,636

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount

Shares reacquired
Class A		(273,525	)		$(3,966,388	)		(311,945	)		$(4,142,094	)
Class B		(496	)		(7,204	)		(2,521	)		(32,865	)
Class C		(13,017	)		(184,933	)		(59,697	)		(780,451	)
Class I		(2,870,450	)		(40,100,305	)		(8,734,942	)		(119,271,353	)
Class R1		(7	)		(95	)		(43	)		(600	)
Class R6		(174,437	)		(2,530,322	)		(1,535,830	)		(20,584,271	)
		(3,331,932	)		$(46,789,247	)		(10,644,978	)		$(144,811,634	)

Net change
Class A		297,723			$4,257,585			772,632			$10,216,429
Class B		(104	)		(1,605	)		1,827			22,754
Class C		19,182			270,793			78,231			1,023,221
Class I		(600,532	)		(7,489,536	)		219,291			(269,655	)
Class R1		472			6,774			1,524			20,635
Class R2		6,451			90,858			582			7,801
Class R3		430			6,180			238			3,033
Class R4		95			1,365			252			3,226
Class R6		1,583,756			22,743,810			470,632			6,284,023
		1,307,473			$19,886,224			1,545,209			$17,311,467

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $658 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)		Change in Unrealized Appreciation or Depreciation		Ending Value
MFS Institutional Money Market Portfolio		$588,609		$34,645,447		$34,281,002		$476		$50		$953,580

Affiliated Issuers									Dividend Income		Capital Gain Distributions
MFS Institutional Money Market Portfolio										$12,281		$—

(8) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

MFS TALK

1-800-637-8255

24 hours a day

ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

Financial advisors

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MAILING ADDRESS

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Kansas City, MO 64121-9341

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Suite 219341

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Kansas City, MO 64105-1407

Semiannual Report

February 29, 2020

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MFS® Low Volatility Equity Fund

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LVU-SEM

MFS® Low Volatility Equity Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			5
Statement of assets and liabilities			10
Statement of operations			12
Statements of changes in net assets			13
Financial highlights			14
Notes to financial statements			23
Proxy voting policies and information			33
Quarterly portfolio disclosure			33
Further information			33
Information about fund contracts and legal claims			33
Provision of financial reports and summary prospectuses			33


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Eli Lilly & Co.			3.2%
Microsoft Corp.			2.9%
Waste Connections, Inc.			2.9%
Costco Wholesale Corp.			2.7%
PepsiCo, Inc.			2.7%
Starbucks Corp.			2.7%
Alphabet, Inc., “A”			2.6%
MetLife, Inc.			2.4%
Amdocs Ltd.			2.4%
Johnson & Johnson			2.4%


GICS equity sectors (g)
Industrials			16.5%
Health Care			16.3%
Information Technology			13.8%
Consumer Staples			11.7%
Financials			11.3%
Utilities			8.4%
Real Estate			7.8%
Communication Services			6.4%
Consumer Discretionary			6.2%
Materials			1.5%
Energy			1.2%

(g)	The Global Industry Classification Standard (GICS®) was developed by and/or is the exclusive property of MSCI, Inc. and S&P Global Market Intelligence Inc. (“S&P Global Market Intelligence”). GICS is a service mark of MSCI and S&P Global Market Intelligence and has been licensed for use by MFS.

From time to time Cash & Cash Equivalents may be negative due to timing of cash receipts and disbursements.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		0.89%		$1,000.00		$981.49		$4.38
A	Hypothetical (h)		0.89%		$1,000.00		$1,020.44		$4.47
B	Actual		1.64%		$1,000.00		$977.09		$8.06
B	Hypothetical (h)		1.64%		$1,000.00		$1,016.71		$8.22
C	Actual		1.64%		$1,000.00		$976.89		$8.06
C	Hypothetical (h)		1.64%		$1,000.00		$1,016.71		$8.22
I	Actual		0.64%		$1,000.00		$982.03		$3.15
I	Hypothetical (h)		0.64%		$1,000.00		$1,021.68		$3.22
R1	Actual		1.64%		$1,000.00		$977.19		$8.06
R1	Hypothetical (h)		1.64%		$1,000.00		$1,016.71		$8.22
R2	Actual		1.14%		$1,000.00		$979.31		$5.61
R2	Hypothetical (h)		1.14%		$1,000.00		$1,019.19		$5.72
R3	Actual		0.89%		$1,000.00		$981.17		$4.38
R3	Hypothetical (h)		0.89%		$1,000.00		$1,020.44		$4.47
R4	Actual		0.64%		$1,000.00		$981.96		$3.15
R4	Hypothetical (h)		0.64%		$1,000.00		$1,021.68		$3.22
R6	Actual		0.56%		$1,000.00		$982.32		$2.76
R6	Hypothetical (h)		0.56%		$1,000.00		$1,022.08		$2.82

(h)	5% class return per year before expenses.

(p)

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 101.1%
Aerospace - 4.9%
CACI International, Inc., “A” (a)		19,865	$	4,867,322
Honeywell International, Inc.		49,496		8,026,766
Lockheed Martin Corp.		16,666		6,164,254
Northrop Grumman Corp.		17,965		5,907,611
United Technologies Corp.		25,014		3,266,578

			$	28,232,531
Automotive - 1.6%
Copart, Inc. (a)		106,232	$	8,974,479

Business Services - 6.0%
Amdocs Ltd.		218,043	$	13,900,241
CoStar Group, Inc. (a)		12,608		8,416,975
FleetCor Technologies, Inc. (a)		10,367		2,755,445
Global Payments, Inc.		34,852		6,411,722
Verisk Analytics, Inc., “A”		18,847		2,923,358

			$	34,407,741
Cable TV - 2.4%
Cable One, Inc.		4,031	$	6,340,844
Charter Communications, Inc., “A” (a)		4,741		2,338,119
Comcast Corp., “A”		124,113		5,017,888

			$	13,696,851
Computer Software - 4.7%
Adobe Systems, Inc. (a)		21,063	$	7,269,263
Microsoft Corp.		103,916		16,835,431
Oracle Corp.		57,492		2,843,554

			$	26,948,248
Construction - 2.4%
AvalonBay Communities, Inc., REIT		31,647	$	6,348,072
Mid-America Apartment Communities, Inc., REIT		34,478		4,456,626
Stanley Black & Decker, Inc.		21,356		3,068,857

			$	13,873,555
Consumer Products - 1.8%
Procter & Gamble Co.		92,595	$	10,484,532

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Consumer Services - 2.2%
Booking Holdings, Inc. (a)		2,232	$	3,784,713
Bright Horizons Family Solutions, Inc. (a)		56,475		8,875,046

			$	12,659,759
Electrical Equipment - 1.6%
AMETEK, Inc.		30,480	$	2,621,280
Johnson Controls International PLC		106,432		3,892,218
TE Connectivity Ltd.		31,097		2,577,009

			$	9,090,507
Electronics - 1.2%
Texas Instruments, Inc.		60,216	$	6,873,054

Energy - Integrated - 1.2%
Chevron Corp.		20,372	$	1,901,523
Exxon Mobil Corp.		91,566		4,710,155

			$	6,611,678
Food & Beverages - 6.8%
General Mills, Inc.		138,418	$	6,782,482
Ingredion, Inc.		117,325		9,773,173
J.M. Smucker Co.		27,972		2,880,836
Mondelez International, Inc.		78,998		4,171,094
PepsiCo, Inc.		116,473		15,377,930

			$	38,985,515
Insurance - 10.2%
Allstate Corp.		42,454	$	4,468,283
Aon PLC		36,552		7,602,816
Chubb Ltd.		44,740		6,488,642
Everest Re Group Ltd.		43,162		10,698,997
Hartford Financial Services Group, Inc.		116,575		5,822,921
Loews Corp.		127,052		5,797,383
MetLife, Inc.		326,662		13,955,001
Reinsurance Group of America, Inc.		26,945		3,288,098

			$	58,122,141
Internet - 3.2%
Alphabet, Inc., “A” (a)		10,986	$	14,713,001
Alphabet, Inc., “C” (a)		2,449		3,280,019

			$	17,993,020

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Machinery & Tools - 3.3%
AGCO Corp.		102,543	$	6,196,674
Eaton Corp. PLC		79,500		7,212,240
Illinois Tool Works, Inc.		15,707		2,635,320
Roper Technologies, Inc.		7,961		2,799,884

			$	18,844,118
Major Banks - 0.7%
PNC Financial Services Group, Inc.		33,165	$	4,192,056

Medical & Health Technology & Services - 1.2%
McKesson Corp.		30,510	$	4,267,129
Quest Diagnostics, Inc.		22,137		2,347,850

			$	6,614,979
Medical Equipment - 6.4%
Danaher Corp.		70,302	$	10,164,263
Medtronic PLC		91,374		9,198,621
STERIS PLC		71,579		11,353,861
Stryker Corp.		17,561		3,346,951
Thermo Fisher Scientific, Inc.		8,374		2,435,159

			$	36,498,855
Natural Gas - Distribution - 0.4%
Sempra Energy		15,353	$	2,146,042

Network & Telecom - 0.5%
Motorola Solutions, Inc.		17,718	$	2,935,518

Other Banks & Diversified Financials - 2.4%
Mastercard, Inc., “A”		24,329	$	7,061,492
U.S. Bancorp		52,391		2,433,038
Visa, Inc., “A”		24,548		4,461,845

			$	13,956,375
Pharmaceuticals - 8.7%
Eli Lilly & Co.		146,101	$	18,427,719
Johnson & Johnson		101,337		13,627,800
Merck & Co., Inc.		44,132		3,378,746
Pfizer, Inc.		274,727		9,181,376
Zoetis, Inc.		39,954		5,323,072

			$	49,938,713

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Pollution Control - 3.9%
Waste Connections, Inc.		169,748	$	16,378,985
Waste Management, Inc.		51,530		5,710,039

			$	22,089,024
Real Estate - 5.9%
EPR Properties, REIT		33,699	$	1,996,329
Extra Space Storage, Inc., REIT		25,732		2,582,464
Public Storage, Inc., REIT		24,584		5,141,006
Spirit Realty Capital, Inc., REIT		124,873		5,681,721
STAG Industrial, Inc., REIT		76,870		2,150,823
STORE Capital Corp., REIT		295,143		9,698,399
Sun Communities, Inc., REIT		42,832		6,548,156

			$	33,798,898
Restaurants - 4.4%
Darden Restaurants, Inc.		25,670	$	2,502,825
McDonald’s Corp.		25,743		4,998,518
Starbucks Corp.		195,563		15,338,006
U.S. Foods Holding Corp. (a)		60,147		2,023,345

			$	24,862,694
Specialty Chemicals - 1.5%
Ecolab, Inc.		47,733	$	8,613,420

Specialty Stores - 2.7%
Costco Wholesale Corp.		54,783	$	15,401,693

Telephone Services - 0.8%
Verizon Communications, Inc.		85,656	$	4,639,129

Utilities - Electric Power - 8.1%
American Electric Power Co., Inc.		39,620	$	3,536,481
Avangrid, Inc.		46,527		2,311,926
DTE Energy Co.		50,473		5,636,320
Duke Energy Corp.		68,474		6,279,066
Evergy, Inc.		71,508		4,673,048
Exelon Corp.		60,520		2,609,017
NextEra Energy, Inc.		41,441		10,474,627
WEC Energy Group, Inc.		25,105		2,317,945
Xcel Energy, Inc.		130,621		8,140,301

			$	45,978,731
Total Common Stocks (Identified Cost, $558,183,169)			$	577,463,856

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Investment Companies (h) - 0.9%
Money Market Funds - 0.9%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $5,315,134)		5,315,030	$	5,315,562

Other Assets, Less Liabilities - (2.0)%			(11,686,322)
Net Assets - 100.0%			$	571,093,096

(a)	Non-income producing security.

(h)

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

REIT

Real Estate Investment Trust

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value (identified cost, $558,183,169)			$577,463,856
Investments in affiliated issuers, at value (identified cost, $5,315,134)			5,315,562
Receivables for
Fund shares sold			5,466,731
Dividends			1,148,193
Other assets			38,671
Total assets			$589,433,013

Liabilities
Payables for
Investments purchased			$3,658,211
Fund shares reacquired			14,422,469
Payable to affiliates
Investment adviser			17,045
Administrative services fee			736
Shareholder servicing costs			201,263
Distribution and service fees			4,960
Accrued expenses and other liabilities			35,233
Total liabilities			$18,339,917
Net assets			$571,093,096

Net assets consist of
Paid-in capital			$549,719,950
Total distributable earnings (loss)			21,373,146
Net assets			$571,093,096
Shares of beneficial interest outstanding			35,916,293

Statement of Assets and Liabilities (unaudited) – continued





	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$115,308,804		7,258,186		$15.89
Class B		2,385,541		150,476		15.85
Class C		28,101,384		1,779,240		15.79
Class I		360,489,221		22,660,068		15.91
Class R1		240,568		15,137		15.89
Class R2		430,619		26,992		15.95
Class R3		567,913		35,622		15.94
Class R4		73,768		4,633		15.92
Class R6		63,495,278		3,985,939		15.93

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $16.86 [100 / 94.25 x $15.89]. On sales of $50,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$5,089,220
Dividends from affiliated issuers	42,371
Other	7,824
Foreign taxes withheld	(8,947	)
Total investment income	$5,130,468
Expenses
Management fee	$1,329,169
Distribution and service fees	280,602
Shareholder servicing costs	207,388
Administrative services fee	39,540
Independent Trustees’ compensation	3,609
Custodian fee	7,223
Shareholder communications	12,995
Audit and tax fees	25,669
Legal fees	984
Registration fees	96,130
Miscellaneous	16,311
Total expenses	$2,019,620
Reduction of expenses by investment adviser and distributor	(55,940	)
Net expenses	$1,963,680
Net investment income (loss)	$3,166,788

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$1,753,357
Affiliated issuers	(2,563	)
Foreign currency	(1	)
Net realized gain (loss)	$1,750,793
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$(20,015,363	)
Affiliated issuers	164
Net unrealized gain (loss)	$(20,015,199	)
Net realized and unrealized gain (loss)	$(18,264,406	)
Change in net assets from operations	$(15,097,618	)

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$3,166,788			$2,128,879
Net realized gain (loss)		1,750,793			567,571
Net unrealized gain (loss)		(20,015,199	)		22,926,394
Change in net assets from operations		$(15,097,618	)		$25,622,844
Total distributions to shareholders		$(3,214,012	)		$(4,818,533	)
Change in net assets from fund share transactions		$201,730,789			$269,731,498
Total change in net assets		$183,419,159			$290,535,809

Net assets
At beginning of period		387,673,937			97,138,128
At end of period		$571,093,096			$387,673,937

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.28			$15.05			$13.77			$12.56			$11.12			$10.82

Income (loss) from investment operations
Net investment income (loss) (d)		$0.09			$0.18			$0.18			$0.16			$0.15			$0.14
Net realized and unrealized gain (loss)		(0.39	)		1.68			1.47			1.23			1.49			0.30	(g)
Total from investment operations		$(0.30	)		$1.86			$1.65			$1.39			$1.64			$0.44

Less distributions declared to shareholders
From net investment income		$(0.07	)		$(0.17	)		$(0.18	)		$(0.15	)		$(0.11	)		$(0.13	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.09	)		$(0.63	)		$(0.37	)		$(0.18	)		$(0.20	)		$(0.14	)
Net asset value, end of period (x)		$15.89			$16.28			$15.05			$13.77			$12.56			$11.12
Total return (%) (r)(s)(t)(x)		(1.85	)(n)		13.23			12.14			11.18			14.87			4.01

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.91	(a)		1.05			1.16			1.33			1.65			2.72
Expenses after expense reductions (f)		0.89	(a)		0.89			0.88			1.16			1.19			1.18
Net investment income (loss)		1.04	(a)		1.22			1.25			1.19			1.25			1.22
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$115,309			$85,022			$41,177			$39,568			$29,508			$11,267

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.25			$15.02			$13.74			$12.53			$11.10			$10.81

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.07			$0.07			$0.06			$0.06			$0.05
Net realized and unrealized gain (loss)		(0.39	)		1.68			1.47			1.23			1.48			0.30	(g)
Total from investment operations		$(0.37	)		$1.75			$1.54			$1.29			$1.54			$0.35

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.06	)		$(0.07	)		$(0.05	)		$(0.02	)		$(0.05	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.03	)		$(0.52	)		$(0.26	)		$(0.08	)		$(0.11	)		$(0.06	)
Net asset value, end of period (x)		$15.85			$16.25			$15.02			$13.74			$12.53			$11.10
Total return (%) (r)(s)(t)(x)		(2.29	)(n)		12.41			11.32			10.36			13.96			3.20

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.66	(a)		1.81			1.91			2.08			2.42			3.79
Expenses after expense reductions (f)		1.64	(a)		1.64			1.64			1.92			1.95			1.95
Net investment income (loss)		0.29	(a)		0.48			0.50			0.43			0.49			0.43
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$2,386			$2,558			$2,211			$2,081			$1,885			$717

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.20			$14.98			$13.70			$12.50			$11.09			$10.80

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.07			$0.07			$0.06			$0.06			$0.05
Net realized and unrealized gain (loss)		(0.39	)		1.67			1.48			1.23			1.48			0.30	(g)
Total from investment operations		$(0.37	)		$1.74			$1.55			$1.29			$1.54			$0.35

Less distributions declared to shareholders
From net investment income		$(0.02	)		$(0.06	)		$(0.08	)		$(0.06	)		$(0.04	)		$(0.05	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.04	)		$(0.52	)		$(0.27	)		$(0.09	)		$(0.13	)		$(0.06	)
Net asset value, end of period (x)		$15.79			$16.20			$14.98			$13.70			$12.50			$11.09
Total return (%) (r)(s)(t)(x)		(2.31	)(n)		12.40			11.36			10.36			13.91			3.23

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.66	(a)		1.81			1.91			2.08			2.31			3.73
Expenses after expense reductions (f)		1.64	(a)		1.64			1.64			1.92			1.95			1.95
Net investment income (loss)		0.29	(a)		0.47			0.50			0.43			0.48			0.43
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$28,101			$21,859			$13,942			$12,422			$9,977			$1,564

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.31			$15.07			$13.78			$12.57			$11.14			$10.84

Income (loss) from investment operations
Net investment income (loss) (d)		$0.11			$0.23			$0.21			$0.19			$0.18			$0.16
Net realized and unrealized gain (loss)		(0.40	)		1.68			1.49			1.23			1.48			0.30	(g)
Total from investment operations		$(0.29	)		$1.91			$1.70			$1.42			$1.66			$0.46

Less distributions declared to shareholders
From net investment income		$(0.09	)		$(0.21	)		$(0.22	)		$(0.18	)		$(0.14	)		$(0.15	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.11	)		$(0.67	)		$(0.41	)		$(0.21	)		$(0.23	)		$(0.16	)
Net asset value, end of period (x)		$15.91			$16.31			$15.07			$13.78			$12.57			$11.14
Total return (%) (r)(s)(t)(x)		(1.80	)(n)		13.55			12.49			11.44			15.05			4.20

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.66	(a)		0.78			0.91			1.07			1.20			2.53
Expenses after expense reductions (f)		0.64	(a)		0.64			0.64			0.92			0.95			0.95
Net investment income (loss)		1.29	(a)		1.46			1.50			1.47			1.51			1.36
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$360,489			$246,245			$30,751			$21,814			$16,123			$964

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.29			$15.06			$13.77			$12.57			$11.12			$10.82

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.07			$0.07			$0.05			$0.06			$0.04
Net realized and unrealized gain (loss)		(0.39	)		1.68			1.48			1.24			1.49			0.31	(g)
Total from investment operations		$(0.37	)		$1.75			$1.55			$1.29			$1.55			$0.35

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.06	)		$(0.07	)		$(0.06	)		$(0.01	)		$(0.04	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.03	)		$(0.52	)		$(0.26	)		$(0.09	)		$(0.10	)		$(0.05	)
Net asset value, end of period (x)		$15.89			$16.29			$15.06			$13.77			$12.57			$11.12
Total return (%) (r)(s)(t)(x)		(2.28	)(n)		12.37			11.36			10.33			13.96			3.18

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.66	(a)		1.81			1.91			2.07			2.56			4.18
Expenses after expense reductions (f)		1.64	(a)		1.64			1.64			1.91			1.95			1.95
Net investment income (loss)		0.27	(a)		0.48			0.49			0.41			0.48			0.39
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$241			$164			$136			$108			$57			$112

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.36			$15.12			$13.83			$12.61			$11.13			$10.83

Income (loss) from investment operations
Net investment income (loss) (d)		$0.07			$0.15			$0.14			$0.12			$0.12			$0.10
Net realized and unrealized gain (loss)		(0.41	)		1.68			1.49			1.25			1.49			0.30	(g)
Total from investment operations		$(0.34	)		$1.83			$1.63			$1.37			$1.61			$0.40

Less distributions declared to shareholders
From net investment income		$(0.05	)		$(0.13	)		$(0.15	)		$(0.12	)		$(0.04	)		$(0.09	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.07	)		$(0.59	)		$(0.34	)		$(0.15	)		$(0.13	)		$(0.10	)
Net asset value, end of period (x)		$15.95			$16.36			$15.12			$13.83			$12.61			$11.13
Total return (%) (r)(s)(t)(x)		(2.07	)(n)		12.94			11.93			10.93			14.57			3.69

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.16	(a)		1.30			1.42			1.58			2.07			3.68
Expenses after expense reductions (f)		1.14	(a)		1.14			1.14			1.42			1.45			1.45
Net investment income (loss)		0.79	(a)		0.98			1.01			0.91			0.98			0.89
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$431			$368			$156			$74			$53			$113

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.34			$15.10			$13.81			$12.59			$11.14			$10.83

Income (loss) from investment operations
Net investment income (loss) (d)		$0.09			$0.19			$0.18			$0.15			$0.15			$0.13
Net realized and unrealized gain (loss)		(0.39	)		1.68			1.48			1.25			1.48			0.31	(g)
Total from investment operations		$(0.30	)		$1.87			$1.66			$1.40			$1.63			$0.44

Less distributions declared to shareholders
From net investment income		$(0.08	)		$(0.17	)		$(0.18	)		$(0.15	)		$(0.09	)		$(0.12	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.10	)		$(0.63	)		$(0.37	)		$(0.18	)		$(0.18	)		$(0.13	)
Net asset value, end of period (x)		$15.94			$16.34			$15.10			$13.81			$12.59			$11.14
Total return (%) (r)(s)(t)(x)		(1.88	)(n)		13.24			12.18			11.22			14.72			4.04

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.91	(a)		1.05			1.16			1.33			1.82			3.43
Expenses after expense reductions (f)		0.89	(a)		0.89			0.89			1.17			1.20			1.20
Net investment income (loss)		1.09	(a)		1.22			1.25			1.18			1.23			1.14
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$568			$100			$67			$59			$53			$113

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.32			$15.08			$13.79			$12.58			$11.14			$10.84

Income (loss) from investment operations
Net investment income (loss) (d)		$0.11			$0.22			$0.21			$0.19			$0.17			$0.16
Net realized and unrealized gain (loss)		(0.40	)		1.69			1.49			1.23			1.49			0.30	(g)
Total from investment operations		$(0.29	)		$1.91			$1.70			$1.42			$1.66			$0.46

Less distributions declared to shareholders
From net investment income		$(0.09	)		$(0.21	)		$(0.22	)		$(0.18	)		$(0.13	)		$(0.15	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.11	)		$(0.67	)		$(0.41	)		$(0.21	)		$(0.22	)		$(0.16	)
Net asset value, end of period (x)		$15.92			$16.32			$15.08			$13.79			$12.58			$11.14
Total return (%) (r)(s)(t)(x)		(1.80	)(n)		13.53			12.48			11.42			15.08			4.20

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.66	(a)		0.81			0.91			1.08			1.57			3.18
Expenses after expense reductions (f)		0.64	(a)		0.64			0.64			0.92			0.95			0.95
Net investment income (loss)		1.29	(a)		1.48			1.50			1.42			1.48			1.39
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$74			$75			$66			$59			$53			$114

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.32			$15.09			$13.80			$12.58			$11.14			$10.84

Income (loss) from investment operations
Net investment income (loss) (d)		$0.12			$0.23			$0.23			$0.18			$0.18			$0.16
Net realized and unrealized gain (loss)		(0.39	)		1.68			1.48			1.27			1.50			0.30	(g)
Total from investment operations		$(0.27	)		$1.91			$1.71			$1.45			$1.68			$0.46

Less distributions declared to shareholders
From net investment income		$(0.10	)		$(0.22	)		$(0.23	)		$(0.20	)		$(0.15	)		$(0.15	)
From net realized gain		(0.02	)		(0.46	)		(0.19	)		(0.03	)		(0.09	)		(0.01	)
Total distributions declared to shareholders		$(0.12	)		$(0.68	)		$(0.42	)		$(0.23	)		$(0.24	)		$(0.16	)
Net asset value, end of period (x)		$15.93			$16.32			$15.09			$13.80			$12.58			$11.14
Total return (%) (r)(s)(t)(x)		(1.71	)(n)		13.56			12.57			11.61			15.21			4.22

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.58	(a)		0.71			0.82			0.97			1.36			3.14
Expenses after expense reductions (f)		0.56	(a)		0.56			0.54			0.78			0.88			0.91
Net investment income (loss)		1.37	(a)		1.53			1.60			1.38			1.53			1.43
Portfolio turnover		15	(n)		28			30			36			38			33
Net assets at end of period (000 omitted)		$63,495			$31,283			$8,632			$6,515			$1,693			$1,593

(a)	Annualized.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(g)	The per share amount varies from the net realized and unrealized gain/loss for the period because of the timing of sales of fund shares and the per share amount of realized and unrealized gains and losses at such time.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Low Volatility Equity Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

In March 2020, the FASB issued Accounting Standards Update 2020-04, Reference Rate Reform (Topic 848) – Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the London Interbank Offered Rate (LIBOR) and other IBOR-based reference rates as of the end of 2021. The temporary relief provided by ASU 2020-04 is effective for certain reference rate-related contract modifications that occur during the period from March 12, 2020 through December 31, 2022. Management is evaluating the impact of ASU 2020-04 on the fund’s investments, derivatives, debt and other contracts that will undergo reference rate-related modifications as a result of the reference rate reform.

Investment Valuations– Equity securities, including restricted equity securities, are generally valued at the last sale or official closing price on their primary market or

Notes to Financial Statements (unaudited) – continued

exchange as provided by a third-party pricing service. Equity securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data.

Notes to Financial Statements (unaudited) – continued

significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Level 1 includes unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes unobservable inputs, which may include the adviser’s own assumptions in determining the fair value of investments. The following is a summary of the levels used as of February 29, 2020 in valuing the fund’s assets or liabilities:



Financial Instruments	Level 1		Level 2		Level 3		Total
Equity Securities		$577,463,856		$—		$—		$577,463,856
Mutual Funds		5,315,562		—		—		5,315,562
Total		$582,779,418		$—		$—		$582,779,418

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.

Book/tax differences primarily relate to wash sale loss deferrals.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$2,003,416
Long-term capital gains		2,815,117

Total distributions		$4,818,533

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$564,484,890
Gross appreciation	36,891,275

Gross depreciation	(18,596,747	)
Net unrealized appreciation (depreciation)	$18,294,528

As of 8/31/19

Undistributed ordinary income	672,340
Undistributed long-term capital gain	678,160
Net unrealized appreciation (depreciation)	38,334,276

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.

Notes to Financial Statements (unaudited) – continued

approximately ten years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$570,647		$1,941,936
Class B		4,567		78,678
Class C		62,248		519,468
Class I		2,252,243		1,788,527
Class R1		444		4,789
Class R2		1,744		6,328
Class R3		1,500		2,871
Class R4		509		2,945
Class R6		320,110		472,991
Total		$3,214,012		$4,818,533

(3) Transactions with Affiliates


Up to $1 billion	0.50	%
In excess of $1 billion and up to $2.5 billion	0.475	%
In excess of $2.5 billion	0.45	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $27,046, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.49% of the fund’s average daily net assets.


Classes
A	B		C		I		R1		R2		R3		R4		R6
0.89%		1.64%		1.64%		0.64%		1.64%		1.14%		0.89%		0.64%		0.57%

This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue at least until December 31, 2020. For the six months ended February 29, 2020, this reduction amounted to $28,363, which is included in the reduction of total expenses in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $73,852 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.25%		$131,679
Class B		0.75%		0.25%		1.00%		1.00%		13,008
Class C		0.75%		0.25%		1.00%		1.00%		133,384
Class R1		0.75%		0.25%		1.00%		1.00%		1,169
Class R2		0.25%		0.25%		0.50%		0.50%		1,024
Class R3		—		0.25%		0.25%		0.25%		338
Total Distribution and Service Fees										$280,602

(d)

(e)



	Amount
Class A		$3,078
Class B		1,368
Class C		1,160

Notes to Financial Statements (unaudited) – continued

six months ended February 29, 2020, the fee was $10,516, which equated to

0.0040% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $196,872.

On September 16, 2019, MFS purchased 867 shares of Class I for an aggregate amount of $14,162.

At February 29, 2020, MFS held approximately 100% of the outstanding shares of Class R4.

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $7,824, which is included in “Other” income in the Statement of Operations.

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short-term obligations, aggregated $303,466,653 and $75,688,444, respectively.

Notes to Financial Statements (unaudited) – continued

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares sold
Class A		2,625,192			$43,853,678			3,235,271			$48,902,099
Class B		3,640			59,763			23,122			339,299
Class C		541,228			8,945,740			647,279			9,609,566
Class I		11,523,457			191,895,732			15,531,431			243,089,354
Class R1		5,058			83,058			1,739			27,454
Class R2		4,402			74,313			11,703			189,116
Class R3		29,570			505,315			1,477			22,634
Class R4		1			12			—			—
Class R6		2,258,093			37,902,698			1,485,520			22,946,373
		16,990,641			$283,320,309			20,937,542			$325,125,895

Shares issued to shareholders in reinvestment of distributions
Class A		34,204			$569,841			141,448			$1,933,913
Class B		272			4,567			5,642			75,618
Class C		3,734			62,227			38,814			519,165
Class I		135,065			2,250,851			127,726			1,787,923
Class R1		26			444			356			4,789
Class R2		104			1,744			464			6,328
Class R3		89			1,500			210			2,871
Class R4		31			509			214			2,944
Class R6		17,776			296,877			28,277			392,678
		191,301			$3,188,560			343,151			$4,726,229

Shares reacquired
Class A		(622,214	)		$(10,407,801	)		(890,885	)		$(13,424,228	)
Class B		(10,832	)		(177,321	)		(18,557	)		(280,249	)
Class C		(115,347	)		(1,949,310	)		(267,226	)		(4,024,024	)
Class I		(4,100,443	)		(68,756,929	)		(2,597,814	)		(39,783,835	)
Class R1		(6	)		(101	)		(1,095	)		(17,588	)
Class R2		(8	)		(128	)		(15	)		(235	)
Class R3		(161	)		(2,736	)		(1	)		(10	)
Class R6		(206,183	)		(3,483,754	)		(169,611	)		(2,590,457	)
		(5,055,194	)		$(84,778,080	)		(3,945,204	)		$(60,120,626	)

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares		Amount
Net change
Class A		2,037,182			$34,015,718			2,485,834		$37,411,784
Class B		(6,920	)		(112,991	)		10,207		134,668
Class C		429,615			7,058,657			418,867		6,104,707
Class I		7,558,079			125,389,654			13,061,343		205,093,442
Class R1		5,078			83,401			1,000		14,655
Class R2		4,498			75,929			12,152		195,209
Class R3		29,498			504,079			1,686		25,495
Class R4		32			521			214		2,944
Class R6		2,069,686			34,715,821			1,344,186		20,748,594
		12,126,748			$201,730,789			17,335,489		$269,731,498

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $727 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)			Change in Unrealized Appreciation or Depreciation		Ending Value
MFS Institutional Money Market Portfolio		$2,645,173		$136,840,980		$134,168,192		$(2,563	)		$164		$5,315,562


Affiliated Issuers										Dividend Income		Capital Gain Distributions
MFS Institutional Money Market Portfolio											$42,371		$—

Notes to Financial Statements (unaudited) – continued

(8) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

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1-800-637-8255

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ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

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MAILING ADDRESS

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Kansas City, MO 64105-1407

Semiannual Report

February 29, 2020

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MFS® New Discovery Fund

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NDF-SEM

MFS® New Discovery Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			5
Statement of assets and liabilities			11
Statement of operations			13
Statements of changes in net assets			14
Financial highlights			15
Notes to financial statements			21
Proxy voting policies and information			32
Quarterly portfolio disclosure			32
Further information			32
Information about fund contracts and legal claims			32
Provision of financial reports and summary prospectuses			32


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Everbridge, Inc.			2.1%
WNS (Holdings) Ltd., ADR			1.8%
CACI International, Inc., “A”			1.7%
QTS Realty Trust, Inc., REIT, “A”			1.7%
PRA Health Sciences, Inc.			1.6%
Rapid7, Inc.			1.6%
Q2 Holdings, Inc.			1.6%
Charles River Laboratories International, Inc.			1.5%
Generac Holdings, Inc.			1.5%
Ollie’s Bargain Outlet Holdings, Inc.			1.4%


GICS equity sectors (g)
Health Care			26.9%
Information Technology			25.3%
Consumer Discretionary			11.7%
Industrials			9.4%
Financials			7.9%
Materials			5.1%
Real Estate			4.8%
Communication Services			2.1%
Consumer Staples			1.9%
Energy			1.2%

(g)	The Global Industry Classification Standard (GICS®) was developed by and/or is the exclusive property of MSCI, Inc. and S&P Global Market Intelligence Inc. (“S&P Global Market Intelligence”). GICS is a service mark of MSCI and S&P Global Market Intelligence and has been licensed for use by MFS.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		1.26%		$1,000.00		$1,026.39		$6.35
A	Hypothetical (h)		1.26%		$1,000.00		$1,018.60		$6.32
B	Actual		2.02%		$1,000.00		$1,022.32		$10.16
B	Hypothetical (h)		2.02%		$1,000.00		$1,014.82		$10.12
C	Actual		2.02%		$1,000.00		$1,022.27		$10.16
C	Hypothetical (h)		2.02%		$1,000.00		$1,014.82		$10.12
I	Actual		1.02%		$1,000.00		$1,027.41		$5.14
I	Hypothetical (h)		1.02%		$1,000.00		$1,019.79		$5.12
R1	Actual		2.02%		$1,000.00		$1,022.56		$10.16
R1	Hypothetical (h)		2.02%		$1,000.00		$1,014.82		$10.12
R2	Actual		1.52%		$1,000.00		$1,025.41		$7.65
R2	Hypothetical (h)		1.52%		$1,000.00		$1,017.30		$7.62
R3	Actual		1.27%		$1,000.00		$1,026.41		$6.40
R3	Hypothetical (h)		1.27%		$1,000.00		$1,018.55		$6.37
R4	Actual		1.02%		$1,000.00		$1,027.79		$5.14
R4	Hypothetical (h)		1.02%		$1,000.00		$1,019.79		$5.12
R6	Actual		0.92%		$1,000.00		$1,028.08		$4.64
R6	Hypothetical (h)		0.92%		$1,000.00		$1,020.29		$4.62

(h)	5% class return per year before expenses.

(p)

Notes to Expense Table

Each class with a Rule12b-1 service fee is subject to a rebate of a portion of such fee. Such rebates are included in the expense ratios above. For Class A shares, this rebate reduced the expense ratio above by 0.01%. See Note 3 in the Notes to Financial Statements for additional information.

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 96.3%
Aerospace - 4.2%
CACI International, Inc., “A” (a)		109,622	$	26,859,583
FLIR Systems, Inc.		464,600		19,731,562
Kratos Defense & Security Solutions, Inc. (a)		1,102,620		17,928,601

			$	64,519,746
Apparel Manufacturers - 1.9%
Levi Strauss & Co., “A”		1,158,662	$	19,685,667
Skechers USA, Inc., “A” (a)		277,118		9,167,064

			$	28,852,731
Automotive - 2.9%
Hella KGaA Hueck & Co.		161,457	$	6,672,012
IAA, Inc. (a)		333,379		14,241,951
Stoneridge, Inc. (a)		588,369		13,002,955
Visteon Corp. (a)		179,594		11,680,793

			$	45,597,711
Biotechnology - 6.1%
10x Genomics, Inc., “A” (a)		83,508	$	6,655,588
Adaptive Biotechnologies Corp. (a)		340,657		9,572,462
Aimmune Therapeutics, Inc. (a)(l)		235,921		5,617,279
Amicus Therapeutics, Inc. (a)		1,125,335		10,741,323
Bio-Techne Corp.		71,172		13,443,679
BioXcel Therapeutics, Inc. (a)		184,955		6,935,812
Immunomedics, Inc. (a)		298,015		4,768,240
Morphosys AG, ADR (a)(l)		300,196		8,012,231
Neurocrine Biosciences, Inc. (a)		84,636		8,015,029
Sarepta Therapeutics, Inc. (a)		39,462		4,517,215
Tricida, Inc. (a)		202,940		6,449,433
Twist Bioscience Corp. (a)		348,738		10,678,358

			$	95,406,649
Brokerage & Asset Managers - 2.8%
Hamilton Lane, Inc., “A”		325,946	$	20,254,284
TMX Group Ltd.		213,682		17,783,882
WisdomTree Investments, Inc.		1,331,260		5,404,916

			$	43,443,082

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Business Services - 4.3%
Endava PLC, ADR (a)		164,846	$	8,745,080
EVO Payments, Inc., “A” (a)		465,840		11,776,435
TriNet Group, Inc. (a)		339,662		17,954,534
WNS (Holdings) Ltd., ADR (a)		427,168		28,124,741

			$	66,600,790
Chemicals - 1.0%
Ingevity Corp. (a)		349,069	$	15,722,068

Computer Software - 9.1%
8x8, Inc. (a)		629,714	$	11,649,709
Altair Engineering, Inc., “A” (a)		365,539		12,720,757
Avalara, Inc. (a)		189,419		16,053,260
Bill.com Holdings, Inc. (a)		96,207		5,460,709
DocuSign, Inc. (a)		133,354		11,509,784
Everbridge, Inc. (a)		302,879		32,002,195
Pagerduty, Inc. (a)		627,017		12,916,550
Paylocity Holding Corp. (a)		129,416		16,761,961
Phreesia, Inc. (a)		272,675		8,463,832
Zendesk, Inc. (a)		182,804		14,498,185

			$	142,036,942
Computer Software - Systems - 6.9%
Box, Inc., “A” (a)		614,878	$	10,299,206
Five9, Inc. (a)		94,545		6,904,621
Pluralsight, Inc., “A” (a)		439,441		7,835,233
Proofpoint, Inc. (a)		109,829		11,713,263
Q2 Holdings, Inc. (a)		326,534		24,610,868
Rapid7, Inc. (a)		550,517		25,488,937
RealPage, Inc. (a)		304,507		19,518,899

			$	106,371,027
Construction - 2.5%
Summit Materials, Inc., “A” (a)		966,377	$	18,883,007
Trex Co., Inc. (a)		216,193		20,678,860

			$	39,561,867
Consumer Services - 3.9%
Bright Horizons Family Solutions, Inc. (a)		121,768	$	19,135,841
MakeMyTrip Ltd. (a)		580,071		13,347,434
OneSpaWorld Holdings Ltd. (l)		737,862		9,016,674
Planet Fitness, Inc. (a)		278,380		18,787,866

			$	60,287,815

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Containers - 0.5%
Gerresheimer AG		114,507	$	8,273,675

Electrical Equipment - 2.8%
CTS Corp.		221,179	$	5,766,136
Generac Holdings, Inc. (a)		230,020		23,689,760
Littlefuse, Inc.		83,107		13,270,526

			$	42,726,422
Electronics - 1.7%
Monolithic Power Systems, Inc.		67,953	$	10,780,064
nLIGHT, Inc. (a)		403,419		6,660,448
Silicon Laboratories, Inc. (a)		94,386		8,370,150

			$	25,810,662
Entertainment - 2.1%
CTS Eventim AG		302,164	$	15,981,942
Manchester United PLC, “A”		936,766		16,384,037

			$	32,365,979
Food & Drug Stores - 1.0%
Grocery Outlet Holding Corp. (a)		493,386	$	15,615,667

Gaming & Lodging - 1.4%
Wyndham Hotels & Resorts, Inc.		426,935	$	21,752,338

General Merchandise - 1.4%
Ollie’s Bargain Outlet Holdings, Inc. (a)		432,742	$	22,013,586

Leisure & Toys - 0.7%
Funko, Inc., “A” (a)(l)		1,278,146	$	10,365,764

Machinery & Tools - 0.6%
Ritchie Bros. Auctioneers, Inc.		246,841	$	9,799,588

Medical & Health Technology & Services - 7.5%
Charles River Laboratories International, Inc. (a)		152,743	$	23,762,229
Guardant Health, Inc. (a)		127,963		11,127,662
HealthEquity, Inc. (a)		195,606		13,886,070
ICON PLC (a)		123,906		19,336,770
PRA Health Sciences, Inc. (a)		271,283		25,554,859
Schrodinger, Inc. (a)		136,550		6,333,189
Teladoc Health, Inc. (a)		130,870		16,353,515

			$	116,354,294

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Medical Equipment - 9.0%
Inspire Medical Systems, Inc. (a)		89,561	$	7,690,603
iRhythm Technologies, Inc. (a)		169,709		14,759,592
Masimo Corp. (a)		95,665		15,624,965
Merit Medical Systems, Inc. (a)		299,337		10,779,125
Nevro Corp. (a)		79,585		10,357,988
OptiNose, Inc. (a)		970,729		5,872,910
OrthoPediatrics Corp. (a)		381,988		17,731,883
PerkinElmer, Inc.		142,682		12,333,432
Quidel Corp. (a)		219,821		16,978,974
Silk Road Medical, Inc. (a)		286,122		11,401,962
STERIS PLC		73,881		11,719,004
TransMedics Group, Inc. (a)(l)		236,061		3,706,158

			$	138,956,596
Network & Telecom - 2.1%
Interxion Holding N.V. (a)		67,139	$	5,699,430
QTS Realty Trust, Inc., REIT, “A”		468,099		26,293,121

			$	31,992,551
Oil Services - 1.0%
Core Laboratories N.V.		422,135	$	11,330,104
Patterson-UTI Energy, Inc.		704,136		4,034,699

			$	15,364,803
Other Banks & Diversified Financials - 5.1%
Bank OZK		245,538	$	6,234,210
Diamond Eagle Acquisition Corp. (a)		646,449		10,356,113
Nebula Acquisition Corp. (a)		910,512		9,760,689
Prosperity Bancshares, Inc.		208,666		13,479,823
Signature Bank		57,324		7,171,232
Texas Capital Bancshares, Inc. (a)		352,504		16,595,888
Wintrust Financial Corp.		297,621		15,895,938

			$	79,493,893
Pharmaceuticals - 3.7%
BridgeBio Pharma, Inc. (a)		202,345	$	6,450,759
Collegium Pharmaceutical, Inc. (a)		323,779		7,689,751
Forty Seven, Inc. (a)		197,921		11,479,418
GW Pharmaceuticals PLC, ADR (a)(l)		104,861		10,728,329
Orchard RX Ltd., ADR (a)		321,588		4,145,269
Principia Biopharma, Inc. (a)		121,315		7,832,097
SpringWorks Therapeutics, Inc. (a)		271,994		8,692,928

			$	57,018,551

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Pollution Control - 0.6%
Casella Waste Systems, Inc., “A” (a)		181,881	$	8,812,134

Railroad & Shipping - 0.2%
StealthGas, Inc. (a)		1,008,631	$	2,753,563

Real Estate - 3.1%
Big Yellow Group PLC, REIT		686,100	$	9,410,232
Industrial Logistics Properties Trust, REIT		906,939		18,737,360
STAG Industrial, Inc., REIT		727,200		20,347,056

			$	48,494,648
Restaurants - 0.9%
Performance Food Group Co. (a)		340,722	$	14,446,613

Special Products & Services - 1.0%
Boyd Group Services, Inc.		101,211	$	15,834,837

Specialty Chemicals - 3.1%
Axalta Coating Systems Ltd. (a)		761,206	$	18,969,253
Ferro Corp. (a)		1,418,219		16,479,705
RPM International, Inc.		146,791		9,410,771
Univar Solutions, Inc. (a)		200,213		3,401,619

			$	48,261,348
Specialty Stores - 0.4%
Hudson Ltd., “A” (a)		717,954	$	6,684,152

Trucking - 0.8%
Schneider National, Inc.		730,810	$	13,088,807
Total Common Stocks (Identified Cost, $1,274,440,191)			$	1,494,680,899

Investment Companies (h) - 5.4%
Money Market Funds - 5.4%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $83,551,167)		83,553,695	$	83,562,050

Collateral for Securities Loaned - 0.9%
State Street Navigator Securities Lending Government Money Market Portfolio, 1.61% (j) (Identified Cost, $14,794,456)		14,794,456	$	14,794,456

Other Assets, Less Liabilities - (2.6)%			(40,523,547)
Net Assets - 100.0%			$	1,552,513,858

Portfolio of Investments (unaudited) – continued

(a)	Non-income producing security.

(h)

(j)	The rate quoted is the annualized seven-day yield of the fund at period end.

(l)	A portion of this security is on loan. See Note 2 for additional information.

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

ADR

American Depositary Receipt

REIT

Real Estate Investment Trust

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value, including $25,454,485 of securities on loan (identified cost, $1,289,234,647)			$1,509,475,355
Investments in affiliated issuers, at value (identified cost, $83,551,167)			83,562,050
Cash			89,283
Receivables for
Investments sold			7,347,996
Fund shares sold			5,518,307
Interest and dividends			465,308
Other assets			4,599
Total assets			$1,606,462,898

Liabilities
Payables for
Investments purchased			$30,220,099
Fund shares reacquired			8,256,797
Collateral for securities loaned, at value (c)			14,794,456
Payable to affiliates
Investment adviser			110,657
Administrative services fee			1,794
Shareholder servicing costs			479,589
Distribution and service fees			18,029
Payable for independent Trustees’ compensation			1,721
Accrued expenses and other liabilities			65,898
Total liabilities			$53,949,040
Net assets			$1,552,513,858

Net assets consist of
Paid-in capital			$1,293,500,001
Total distributable earnings (loss)			259,013,857
Net assets			$1,552,513,858
Shares of beneficial interest outstanding			56,424,570

(c)	Non-cash collateral is not included.

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$587,644,047		22,498,719		$26.12
Class B		16,246,948		853,926		19.03
Class C		55,449,448		2,905,569		19.08
Class I		203,751,364		6,795,116		29.98
Class R1		4,205,437		223,522		18.81
Class R2		26,965,817		1,128,385		23.90
Class R3		56,704,137		2,174,776		26.07
Class R4		12,269,438		436,809		28.09
Class R6		589,277,222		19,407,748		30.36

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $27.71 [100 / 94.25 x $26.12]. On sales of $50,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$4,527,695
Dividends from affiliated issuers	517,114
Income on securities loaned	470,669
Other	41,345
Foreign taxes withheld	(213,576	)
Total investment income	$5,343,247
Expenses
Management fee	$6,674,918
Distribution and service fees	1,292,135
Shareholder servicing costs	611,307
Administrative services fee	104,374
Independent Trustees’ compensation	12,358
Custodian fee	53,464
Shareholder communications	59,924
Audit and tax fees	29,603
Legal fees	5,917
Miscellaneous	111,059
Total expenses	$8,955,059
Reduction of expenses by investment adviser and distributor	(94,552	)
Net expenses	$8,860,507
Net investment income (loss)	$(3,517,260	)

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$57,443,614
Affiliated issuers	(922	)
Foreign currency	(1,356	)
Net realized gain (loss)	$57,441,336
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$(18,849,895	)
Affiliated issuers	1,492
Translation of assets and liabilities in foreign currencies	16,623
Net unrealized gain (loss)	$(18,831,780	)
Net realized and unrealized gain (loss)	$38,609,556
Change in net assets from operations	$35,092,296

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$(3,517,260	)		$(7,785,281	)
Net realized gain (loss)		57,441,336			164,304,985
Net unrealized gain (loss)		(18,831,780	)		(111,646,966	)
Change in net assets from operations		$35,092,296			$44,872,738
Total distributions to shareholders		$(114,138,918	)		$(230,450,032	)
Change in net assets from fund share transactions		$200,103,192			$236,885,028
Total change in net assets		$121,056,570			$51,307,734

Net assets
At beginning of period		1,431,457,288			1,380,149,554
At end of period		$1,552,513,858			$1,431,457,288

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$27.56			$33.30			$27.27			$24.11			$23.69			$25.49

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.08	)		$(0.19	)		$(0.23	)		$(0.18	)(c)		$(0.11	)		$(0.20	)
Net realized and unrealized gain (loss)		0.88			0.06	(g)		9.07			3.92			0.53			0.22
Total from investment operations		$0.80			$(0.13	)		$8.84			$3.74			$0.42			$0.02

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$26.12			$27.56			$33.30			$27.27			$24.11			$23.69
Total return (%) (r)(s)(t)(x)		2.64	(n)		3.49			34.98			15.83	(c)		1.77			0.47

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.28	(a)		1.30			1.33			1.35	(c)		1.36			1.36
Expenses after expense reductions (f)		1.26	(a)		1.29			1.31			1.33	(c)		1.34			1.31
Net investment income (loss)		(0.57	)(a)		(0.70	)		(0.80	)		(0.70	)(c)		(0.50	)		(0.81	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$587,644			$549,660			$525,698			$394,878			$400,997			$457,437

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$20.72			$26.86			$22.65			$20.27			$20.07			$22.04

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.14	)		$(0.30	)		$(0.37	)		$(0.30	)(c)		$(0.24	)		$(0.32	)
Net realized and unrealized gain (loss)		0.69			(0.23	)(g)		7.39			3.26			0.44			0.17
Total from investment operations		$0.55			$(0.53	)		$7.02			$2.96			$0.20			$(0.15	)

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$19.03			$20.72			$26.86			$22.65			$20.27			$20.07
Total return (%) (r)(s)(t)(x)		2.29	(n)		2.69			34.00			14.97	(c)		1.00			(0.27	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		2.03	(a)		2.06			2.08			2.10	(c)		2.11			2.11
Expenses after expense reductions (f)		2.02	(a)		2.04			2.06			2.08	(c)		2.09			2.06
Net investment income (loss)		(1.32	)(a)		(1.45	)		(1.55	)		(1.45	)(c)		(1.26	)		(1.57	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$16,247			$18,708			$23,424			$20,143			$22,906			$27,455

	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$20.78			$26.91			$22.70			$20.31			$20.11			$22.08

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.14	)		$(0.30	)		$(0.37	)		$(0.31	)(c)		$(0.24	)		$(0.32	)
Net realized and unrealized gain (loss)		0.68			(0.22	)(g)		7.39			3.28			0.44			0.17
Total from investment operations		$0.54			$(0.52	)		$7.02			$2.97			$0.20			$(0.15	)

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$19.08			$20.78			$26.91			$22.70			$20.31			$20.11
Total return (%) (r)(s)(t)(x)		2.23	(n)		2.72			33.92			14.99	(c)		0.99			(0.28	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		2.03	(a)		2.05			2.08			2.10	(c)		2.11			2.11
Expenses after expense reductions (f)		2.02	(a)		2.04			2.07			2.09	(c)		2.09			2.06
Net investment income (loss)		(1.32	)(a)		(1.45	)		(1.55	)		(1.45	)(c)		(1.27	)		(1.57	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$55,449			$59,253			$69,498			$76,724			$85,370			$105,686

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$31.29			$36.82			$29.81			$26.24			$25.72			$27.44

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.05	)		$(0.14	)		$(0.18	)		$(0.12	)(c)		$(0.07	)		$(0.14	)
Net realized and unrealized gain (loss)		0.98			0.22	(g)		10.00			4.27			0.59			0.24
Total from investment operations		$0.93			$0.08			$9.82			$4.15			$0.52			$0.10

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$29.98			$31.29			$36.82			$29.81			$26.24			$25.72
Total return (%) (r)(s)(t)(x)		2.74	(n)		3.76			35.31			16.12	(c)		2.02			0.74

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.03	(a)		1.05			1.08			1.10	(c)		1.12			1.11
Expenses after expense reductions (f)		1.02	(a)		1.05			1.07			1.09	(c)		1.09			1.06
Net investment income (loss)		(0.33	)(a)		(0.45	)		(0.55	)		(0.45	)(c)		(0.30	)		(0.55	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$203,751			$164,593			$180,591			$106,459			$101,635			$166,513

	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$20.51			$26.66			$22.50			$20.15			$19.94			$21.91

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.14	)		$(0.30	)		$(0.37	)		$(0.30	)(c)		$(0.23	)		$(0.32	)
Net realized and unrealized gain (loss)		0.68			(0.24	)(g)		7.34			3.23			0.44			0.17
Total from investment operations		$0.54			$(0.54	)		$6.97			$2.93			$0.21			$(0.15	)

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$18.81			$20.51			$26.66			$22.50			$20.15			$19.94
Total return (%) (r)(s)(t)(x)		2.26	(n)		2.67			34.01			14.91	(c)		1.05			(0.28	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		2.03	(a)		2.05			2.08			2.10	(c)		2.11			2.11
Expenses after expense reductions (f)		2.02	(a)		2.05			2.07			2.09	(c)		2.09			2.06
Net investment income (loss)		(1.32	)(a)		(1.45	)		(1.55	)		(1.45	)(c)		(1.26	)		(1.57	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$4,205			$4,652			$5,342			$4,377			$5,647			$6,573

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$25.42			$31.31			$25.85			$22.95			$22.60			$24.46

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.10	)		$(0.24	)		$(0.29	)		$(0.23	)(c)		$(0.17	)		$(0.25	)
Net realized and unrealized gain (loss)		0.82			(0.04	)(g)		8.56			3.71			0.52			0.21
Total from investment operations		$0.72			$(0.28	)		$8.27			$3.48			$0.35			$(0.04	)

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$23.90			$25.42			$31.31			$25.85			$22.95			$22.60
Total return (%) (r)(s)(t)(x)		2.54	(n)		3.19			34.68			15.50	(c)		1.55			0.23

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.53	(a)		1.56			1.58			1.60	(c)		1.62			1.61
Expenses after expense reductions (f)		1.52	(a)		1.54			1.57			1.59	(c)		1.59			1.56
Net investment income (loss)		(0.82	)(a)		(0.95	)		(1.05	)		(0.95	)(c)		(0.82	)		(1.07	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$26,966			$32,381			$36,272			$29,130			$35,890			$57,077

	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$27.51			$33.26			$27.24			$24.09			$23.67			$25.47

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.08	)		$(0.19	)		$(0.24	)		$(0.17	)(c)		$(0.12	)		$(0.20	)
Net realized and unrealized gain (loss)		0.88			0.05	(g)		9.07			3.90			0.54			0.22
Total from investment operations		$0.80			$(0.14	)		$8.83			$3.73			$0.42			$0.02

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$26.07			$27.51			$33.26			$27.24			$24.09			$23.67
Total return (%) (r)(s)(t)(x)		2.64	(n)		3.45			34.98			15.81	(c)		1.77			0.47

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.28	(a)		1.30			1.33			1.35	(c)		1.37			1.36
Expenses after expense reductions (f)		1.27	(a)		1.30			1.32			1.34	(c)		1.34			1.31
Net investment income (loss)		(0.58	)(a)		(0.70	)		(0.80	)		(0.70	)(c)		(0.55	)		(0.82	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$56,704			$52,559			$50,895			$42,346			$57,593			$89,659

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$29.44			$35.05			$28.48			$25.09			$24.60			$26.33

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.05	)		$(0.13	)		$(0.15	)		$(0.12	)(c)		$(0.07	)		$(0.14	)
Net realized and unrealized gain (loss)		0.94			0.13	(g)		9.53			4.09			0.56			0.23
Total from investment operations		$0.89			$0.00	(w)		$9.38			$3.97			$0.49			$0.09

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$28.09			$29.44			$35.05			$28.48			$25.09			$24.60
Total return (%) (r)(s)(t)(x)		2.78	(n)		3.72			35.42			16.14	(c)		1.99			0.73

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.03	(a)		1.05			1.08			1.10	(c)		1.12			1.11
Expenses after expense reductions (f)		1.02	(a)		1.05			1.07			1.09	(c)		1.09			1.06
Net investment income (loss)		(0.34	)(a)		(0.45	)		(0.51	)		(0.45	)(c)		(0.32	)		(0.57	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$12,269			$8,384			$10,612			$83,186			$91,974			$142,857

	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$31.64			$37.13			$30.01			$26.38			$25.83			$27.52

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.04	)		$(0.11	)		$(0.14	)		$(0.09	)(c)		$(0.03	)		$(0.12	)
Net realized and unrealized gain (loss)		1.00			0.23	(g)		10.07			4.30			0.58			0.25
Total from investment operations		$0.96			$0.12			$9.93			$4.21			$0.55			$0.13

Less distributions declared to shareholders
From net realized gain		$(2.24	)		$(5.61	)		$(2.81	)		$(0.58	)		$—			$(1.82	)
Net asset value, end of period (x)		$30.36			$31.64			$37.13			$30.01			$26.38			$25.83
Total return (%) (r)(s)(t)(x)		2.81	(n)		3.85			35.45			16.26	(c)		2.13			0.85

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.93	(a)		0.96			0.97			0.98	(c)		0.99			0.98
Expenses after expense reductions (f)		0.92	(a)		0.95			0.96			0.97	(c)		0.97			0.93
Net investment income (loss)		(0.23	)(a)		(0.35	)		(0.44	)		(0.34	)(c)		(0.11	)		(0.44	)
Portfolio turnover		24	(n)		69			67			53			49			56
Net assets at end of period (000 omitted)		$589,277			$541,266			$477,818			$385,440			$320,645			$313,080

See Notes to Financial Statements

Financial Highlights – continued

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(g)	The per share amount varies from the net realized and unrealized gain/loss for the period because of the timing of sales of fund shares and the per share amount of realized and unrealized gains and losses at such time.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(w)	Per share amount was less than $0.01.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS New Discovery Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

General– The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued. The fund will generally focus on securities of small size companies which may be more volatile than those of larger companies. The fund invests in foreign securities. Investments in foreign securities are vulnerable to the effects of changes in the relative values of the local currency and the U.S. dollar and to the effects of changes in each country’s market, economic, industrial, political, regulatory, geopolitical, and other conditions.

Notes to Financial Statements (unaudited) – continued

subject. Balance sheet offsetting disclosures, to the extent applicable to the fund, have been included in the fund’s Significant Accounting Policies note under the captions for each of the fund’sin-scope financial instruments and transactions.

Investment Valuations– Equity securities, including restricted equity securities, are generally valued at the last sale or official closing price on their primary market or exchange as provided by a third-party pricing service. Equity securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

Notes to Financial Statements (unaudited) – continued

published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.



Financial Instruments	Level 1		Level 2		Level 3		Total
Equity Securities:
United States		$1,293,647,847		$—		$—		$1,293,647,847
United Kingdom		40,002,715		9,410,232		—		49,412,947
Canada		43,418,307		—		—		43,418,307
India		41,472,175		—		—		41,472,175
Germany		8,012,231		30,927,629		—		38,939,860
Ireland		19,336,770		—		—		19,336,770
Netherlands		5,699,430		—		—		5,699,430
Greece		2,753,563		—		—		2,753,563
Mutual Funds		98,356,506		—		—		98,356,506
Total		$1,552,699,544		$40,337,861		$—		$1,593,037,405

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

related securities must be returned within the earlier of the standard trade settlement period for such securities or within three business days. The loans are collateralized by cash and/or U.S. Treasury and federal agency obligations in an amount typically at least equal to the market value of the securities loaned. On loans collateralized by cash, the cash collateral is invested in a money market fund. The market value of the loaned securities is determined at the close of business of the fund and any additional required collateral is delivered to the fund on the next business day. The lending agent provides the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. At period end, the fund had investment securities on loan, all of which were classified as equity securities in the fund’s Portfolio of Investments, with a fair value of $25,454,485. The fair value of the fund’s investment securities on loan and a related liability of $14,794,456 for cash collateral received on securities loaned are both presented gross in the Statement of Assets and Liabilities. Additionally, these loans were collateralized by U.S. Treasury Obligations of $11,731,690 held by the lending agent. The collateral on securities loaned exceeded the value of securities on loan at period end. The liability for cash collateral for securities loaned is carried at fair value, which is categorized as level 2 within the fair value hierarchy. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income.

Notes to Financial Statements (unaudited) – continued

gain/loss if the security is still held by the fund. Any other proceeds from litigation not related to portfolio holdings are reflected as other income in the Statement of Operations.

Book/tax differences primarily relate to wash sale loss deferrals and treating a portion of the proceeds from redemptions as a distribution for tax purposes.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$77,700,077
Long-term capital gains		152,749,955

Total distributions		$230,450,032

Notes to Financial Statements (unaudited) – continued

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$1,377,738,857
Gross appreciation	353,357,680

Gross depreciation	(138,059,132	)
Net unrealized appreciation (depreciation)	$215,298,548

As of 8/31/19

Undistributed ordinary income	33,529,410
Undistributed long-term capital gain	70,388,231
Other temporary differences	(4,113	)
Net unrealized appreciation (depreciation)	234,146,951

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$45,480,404		$88,854,670
Class B		1,857,992		4,829,407
Class C		5,934,396		13,810,640
Class I		12,867,161		26,484,311
Class R1		463,207		1,085,473
Class R2		2,558,232		6,518,565
Class R3		4,552,802		8,385,161
Class R4		737,611		1,643,025
Class R6		39,687,113		78,838,780
Total		$114,138,918		$230,450,032

(3) Transactions with Affiliates

Investment Adviser– The fund has an investment advisory agreement with MFS to provide overall investment management and related administrative services and

Notes to Financial Statements (unaudited) – continued

facilities to the fund. The management fee is computed daily and paid monthly at the following annual rates based on the fund’s average daily net assets:


Up to $1 billion	0.90	%
In excess of $1 billion and up to $2.5 billion	0.80	%
In excess of $2.5 billion and up to $5 billion	0.75	%
In excess of $5 billion	0.70	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $78,377, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.85% of the fund’s average daily net assets.

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $160,815 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.24%		$736,783
Class B		0.75%		0.25%		1.00%		1.00%		90,496
Class C		0.75%		0.25%		1.00%		1.00%		293,069
Class R1		0.75%		0.25%		1.00%		1.00%		22,648
Class R2		0.25%		0.25%		0.50%		0.50%		76,507
Class R3		—		0.25%		0.25%		0.25%		72,632
Total Distribution and Service Fees										$1,292,135

(d)

(e)

Notes to Financial Statements (unaudited) – continued



	Amount
Class A		$9,860
Class B		5,099
Class C		1,321

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $82,415, which equated to 0.0107% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $528,892.

Notes to Financial Statements (unaudited) – continued

the fund engaged in purchase and sale transactions pursuant to this policy, which amounted to $499,240 and $460,164, respectively. The sales transactions resulted in net realized gains (losses) of $(178,021).

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $41,345, which is included in “Other” income in the Statement of Operations.

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short-term obligations, aggregated $429,056,663 and $352,111,655, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20				Year ended 8/31/19

	Shares		Amount		Shares		Amount
Shares sold
Class A		3,012,509		$84,471,604		4,174,526		$111,128,979
Class B		6,826		139,418		119,514		2,451,739
Class C		319,517		6,592,765		582,894		11,635,600
Class I		2,493,453		80,116,218		2,246,267		67,695,575
Class R1		13,293		271,635		48,692		1,012,673
Class R2		123,496		3,177,248		283,452		6,968,591
Class R3		523,654		14,515,424		470,712		12,582,867
Class R4		226,472		6,794,736		85,788		2,403,986
Class R6		2,795,482		90,259,561		4,412,506		134,149,812
		9,514,702		$286,338,609		12,424,351		$350,029,822

Shares issued to shareholders in reinvestment of distributions
Class A		1,649,802		$44,577,655		3,869,394		$86,751,808
Class B		91,737		1,809,047		272,245		4,614,555
Class C		262,614		5,194,497		703,090		11,952,526
Class I		370,322		11,483,689		930,538		23,644,963
Class R1		23,754		463,207		64,689		1,085,473
Class R2		96,986		2,399,424		284,154		5,887,667
Class R3		168,747		4,552,802		374,505		8,385,161
Class R4		25,391		737,611		68,717		1,643,025
Class R6		1,195,889		37,538,966		2,885,648		74,103,434
		3,885,242		$108,756,898		9,452,980		$218,068,612

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares reacquired
Class A		(2,109,033	)		$(59,032,494	)		(3,885,501	)		$(100,360,171	)
Class B		(147,473	)		(3,070,222	)		(361,062	)		(7,129,308	)
Class C		(528,298	)		(10,957,059	)		(1,016,652	)		(20,620,050	)
Class I		(1,329,358	)		(42,325,571	)		(2,820,194	)		(80,345,484	)
Class R1		(40,278	)		(828,188	)		(87,036	)		(1,774,307	)
Class R2		(365,728	)		(9,364,170	)		(452,605	)		(10,891,533	)
Class R3		(427,901	)		(11,844,271	)		(465,291	)		(12,527,864	)
Class R4		(99,818	)		(2,991,202	)		(172,526	)		(5,073,303	)
Class R6		(1,690,141	)		(54,579,138	)		(3,059,304	)		(92,491,386	)
		(6,738,028	)		$(194,992,315	)		(12,320,171	)		$(331,213,406	)

Net change
Class A		2,553,278			$70,016,765			4,158,419			$97,520,616
Class B		(48,910	)		(1,121,757	)		30,697			(63,014	)
Class C		53,833			830,203			269,332			2,968,076
Class I		1,534,417			49,274,336			356,611			10,995,054
Class R1		(3,231	)		(93,346	)		26,345			323,839
Class R2		(145,246	)		(3,787,498	)		115,001			1,964,725
Class R3		264,500			7,223,955			379,926			8,440,164
Class R4		152,045			4,541,145			(18,021	)		(1,026,292	)
Class R6		2,301,230			73,219,389			4,238,850			115,761,860
		6,661,916			$200,103,192			9,557,160			$236,885,028

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

The fund is one of several mutual funds in which certain MFS funds may invest. The MFS funds do not invest in the underlying funds for the purpose of exercising management or control. At the end of the period, the MFS Growth Allocation Fund, the MFS Moderate Allocation Fund, the MFS Aggressive Growth Allocation Fund, and the MFS Conservative Allocation Fund were the owners of record of approximately 7%, 6%, 3%, and 2%, respectively, of the value of outstanding voting shares of the fund. In addition, the MFS Lifetime 2020 Fund, the MFS Lifetime 2025 Fund, the MFS Lifetime 2030 Fund, the MFS Lifetime 2035 Fund, the MFS Lifetime 2040 Fund, the MFS Lifetime 2045 Fund, the MFS Lifetime 2050 Fund, the MFS Lifetime 2055 Fund, the MFS Lifetime 2060 Fund, and the MFS Lifetime Income Fund were each the owners of record of less than 1% of the value of outstanding voting shares of the fund.

(6) Line of Credit

Notes to Financial Statements (unaudited) – continued

financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $3,766 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)			Change in Unrealized Appreciation or Depreciation		Ending Value
MFS Institutional Money Market Portfolio		$48,505,120		$189,415,034		$154,358,674		$(922	)		$1,492		$83,562,050

Affiliated Issuers										Dividend Income		Capital Gain Distributions
MFS Institutional Money Market Portfolio											$517,114		$—

(8) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

MFS TALK

1-800-637-8255

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ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

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MAILING ADDRESS

MFS Service Center, Inc.

P.O. Box 219341

Kansas City, MO 64121-9341

OVERNIGHT MAIL

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Kansas City, MO 64105-1407

Semiannual Report

February 29, 2020

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MFS® Research International Fund

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RIF-SEM

MFS® Research International Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			4
Portfolio of investments			6
Statement of assets and liabilities			12
Statement of operations			14
Statements of changes in net assets			15
Financial highlights			16
Notes to financial statements			28
Proxy voting policies and information			40
Quarterly portfolio disclosure			40
Further information			40
Information about fund contracts and legal claims			40
Provision of financial reports and summary prospectuses			40


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Nestle S.A.			3.4%
Roche Holding AG			3.3%
Schneider Electric S.A.			2.5%
Linde PLC			2.4%
Novo Nordisk A.S., “B”			2.1%
AIA Group Ltd.			1.9%
LVMH Moet Hennessy Louis Vuitton SE			1.8%
Daikin Industries Ltd.			1.6%
Aon PLC			1.6%
BNP Paribas			1.5%

Global equity sectors (k)
Capital Goods			22.5%
Financial Services			22.0%
Health Care			11.9%
Technology			11.7%
Consumer Staples			9.9%
Consumer Cyclicals			8.7%
Energy			8.4%
Telecommunications/Cable Television			4.0%


Issuer country weightings (x)
Japan			19.8%
Switzerland			13.9%
France			11.9%
Germany			7.6%
United Kingdom			7.5%
United States			7.1%
Hong Kong			4.8%
Netherlands			2.9%
Spain			2.9%
Other Countries			21.6%

Currency exposure weightings (y)
Euro			33.3%
Japanese Yen			19.8%
Swiss Franc			13.9%
British Pound Sterling			7.2%
United States Dollar			6.7%
Hong Kong Dollar			5.2%
Australian Dollar			2.9%
Danish Krone			2.7%
Taiwan Dollar			1.6%
Other Currencies			6.7%

(k)	The sectors set forth above and the associated portfolio composition are based on MFS’ own custom sector classification methodology.

(x)	Represents the portfolio’s exposure to issuer countries as a percentage of a portfolio’s net assets. For purposes of this presentation, United States includes Cash & Cash Equivalents.

(y)	Represents the portfolio’s exposure to a particular currency as a percentage of a portfolio’s net assets. For purposes of this presentation, United States Dollar includes Cash & Cash Equivalents.

Portfolio Composition – continued

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		1.05%		$1,000.00		$1,027.11		$5.29
A	Hypothetical (h)		1.05%		$1,000.00		$1,019.64		$5.27
B	Actual		1.81%		$1,000.00		$1,023.68		$9.11
B	Hypothetical (h)		1.81%		$1,000.00		$1,015.86		$9.07
C	Actual		1.81%		$1,000.00		$1,022.93		$9.10
C	Hypothetical (h)		1.81%		$1,000.00		$1,015.86		$9.07
I	Actual		0.81%		$1,000.00		$1,028.39		$4.09
I	Hypothetical (h)		0.81%		$1,000.00		$1,020.84		$4.07
R1	Actual		1.81%		$1,000.00		$1,023.38		$9.11
R1	Hypothetical (h)		1.81%		$1,000.00		$1,015.86		$9.07
R2	Actual		1.30%		$1,000.00		$1,025.98		$6.55
R2	Hypothetical (h)		1.30%		$1,000.00		$1,018.40		$6.52
R3	Actual		1.06%		$1,000.00		$1,027.21		$5.34
R3	Hypothetical (h)		1.06%		$1,000.00		$1,019.59		$5.32
R4	Actual		0.81%		$1,000.00		$1,028.42		$4.09
R4	Hypothetical (h)		0.81%		$1,000.00		$1,020.84		$4.07
R6	Actual		0.70%		$1,000.00		$1,029.14		$3.53
R6	Hypothetical (h)		0.70%		$1,000.00		$1,021.38		$3.52
529A	Actual		1.09%		$1,000.00		$1,027.37		$5.49
529A	Hypothetical (h)		1.09%		$1,000.00		$1,019.44		$5.47
529B	Actual		1.85%		$1,000.00		$1,023.55		$9.31
529B	Hypothetical (h)		1.85%		$1,000.00		$1,015.66		$9.27
529C	Actual		1.85%		$1,000.00		$1,023.64		$9.31
529C	Hypothetical (h)		1.85%		$1,000.00		$1,015.66		$9.27

(h)	5% class return per year before expenses.

(p)

Notes to Expense Table

Each class with a Rule12b-1 service fee is subject to a rebate of a portion of such fee. Such rebates are included in the expense ratios above. For Class 529A and Class 529C shares, this rebate reduced the expense ratios above by 0.02% and 0.01%, respectively. See Note 3 in the Notes to Financial Statements for additional information.

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 99.1%
Airlines - 1.0%
Aena S.A.		276,052	$	44,435,555
Malaysia Airports Holdings Berhad		8,399,400		13,179,551
Ryanair Holdings PLC, ADR (a)		496,964		35,622,380

			$	93,237,486
Alcoholic Beverages - 0.3%
Ambev S.A., ADR		8,511,277	$	27,321,199

Apparel Manufacturers - 3.6%
Adidas AG		395,250	$	110,124,093
Compagnie Financiere Richemont S.A.		1,090,445		74,887,141
LVMH Moet Hennessy Louis Vuitton SE		420,382		173,440,573

			$	358,451,807
Automotive - 1.6%
Koito Manufacturing Co. Ltd.		1,726,000	$	69,557,682
USS Co. Ltd.		5,474,500		86,290,943

			$	155,848,625
Brokerage & Asset Managers - 2.3%
Euronext N.V.		1,697,035	$	141,675,758
Hong Kong Exchanges & Clearing Ltd.		2,466,200		81,562,578

			$	223,238,336
Business Services - 0.7%
Nomura Research Institute Ltd.		2,994,000	$	66,483,768

Computer Software - 1.2%
Cadence Design Systems, Inc. (a)		560,124	$	37,046,601
Check Point Software Technologies Ltd. (a)		751,277		77,982,553

			$	115,029,154
Computer Software - Systems - 3.9%
Amadeus IT Group S.A.		1,380,849	$	97,836,930
Constellation Software, Inc.		57,388		58,464,573
EPAM Systems, Inc. (a)		213,349		47,619,497
Fujitsu Ltd.		793,900		83,783,320
Hitachi Ltd.		2,923,300		98,056,192

			$	385,760,512

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Conglomerates - 0.5%
Melrose Industries PLC		19,251,400	$	52,536,472

Construction - 2.1%
Techtronic Industries Co. Ltd.		14,440,000	$	118,039,535
Toto Ltd.		2,459,800		92,742,601

			$	210,782,136
Consumer Products - 3.2%
Kao Corp.		1,287,600	$	93,706,108
L’Oréal		423,659		113,941,211
Reckitt Benckiser Group PLC		1,488,769		109,892,082

			$	317,539,401
Consumer Services - 1.2%
51job, Inc., ADR (a)		574,895	$	42,984,899
Carsales.com Ltd.		1,373,555		14,211,148
Persol Holdings Co. Ltd.		2,543,700		33,565,702
SEEK Ltd.		1,725,255		22,867,572

			$	113,629,321
Containers - 0.9%
Brambles Ltd.		11,703,812	$	90,092,973

Electrical Equipment - 3.7%
Legrand S.A.		1,510,077	$	116,580,287
Schneider Electric SE		2,430,202		247,694,019

			$	364,274,306
Electronics - 4.3%
Kyocera Corp.		1,178,000	$	73,831,801
Mellanox Technologies Ltd. (a)		523,922		62,566,765
NXP Semiconductors N.V.		451,736		51,357,866
Samsung Electronics Co. Ltd.		1,671,990		75,640,860
Silicon Motion Technology Corp., ADR		1,077,195		40,093,198
Taiwan Semiconductor Manufacturing Co. Ltd.		11,473,326		117,638,910

			$	421,129,400
Energy - Independent - 0.4%
Oil Search Ltd.		12,440,882	$	43,675,723

Energy - Integrated - 3.9%
BP PLC		25,395,782	$	131,545,228
Cairn Energy PLC (a)		21,935,995		39,786,350
Eni S.p.A.		5,959,185		73,771,740
Galp Energia SGPS S.A., “B”		6,011,259		82,515,549

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued

Energy - Integrated - continued
Idemitsu Kosan Co. Ltd.		2,135,700	$	52,312,130

			$	379,930,997
Food & Beverages - 4.4%
Danone S.A.		1,380,420	$	97,726,097
Nestle S.A.		3,189,863		330,491,982

			$	428,218,079
Gaming & Lodging - 0.4%
Flutter Entertainment PLC		338,339	$	36,106,871

Insurance - 6.2%
AIA Group Ltd.		19,437,000	$	187,984,840
Aon PLC		759,373		157,949,584
Hiscox Ltd.		5,500,637		87,341,968
Swiss Re Ltd.		650,032		62,070,914
Zurich Insurance Group AG		308,623		120,106,379

			$	615,453,685
Internet - 1.3%
NAVER Corp.		475,517	$	69,112,901
Scout24 AG		852,592		55,920,873

			$	125,033,774
Machinery & Tools - 4.9%
Daikin Industries Ltd.		1,184,900	$	160,896,764
GEA Group AG		2,390,851		63,294,119
Kubota Corp.		7,489,000		104,889,094
Ritchie Bros. Auctioneers, Inc.		1,504,869		59,679,029
Schindler Holding AG		433,932		97,633,835

			$	486,392,841
Major Banks - 3.9%
BNP Paribas		2,960,642	$	144,661,947
Mitsubishi UFJ Financial Group, Inc.		23,156,300		113,598,660
UBS Group AG		11,560,616		128,047,290

			$	386,307,897
Medical & Health Technology & Services - 0.6%
Sonic Healthcare Ltd.		3,104,494	$	57,543,627

Medical Equipment - 2.4%
EssilorLuxottica		1,009,453	$	139,134,348
Terumo Corp.		3,145,100		100,754,916

			$	239,889,264

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Natural Gas - Distribution - 0.4%
China Resources Gas Group Ltd.		8,094,000	$	40,576,918

Natural Gas - Pipeline - 0.8%
APA Group		7,862,277	$	54,352,086
TC Energy Corp.		549,463		28,638,802

			$	82,990,888
Network & Telecom - 0.4%
LM Ericsson Telephone Co., “B”		5,286,580	$	42,185,471

Other Banks & Diversified Financials - 6.8%
AEON Financial Service Co. Ltd. (l)		5,426,400	$	78,377,919
AIB Group PLC		26,354,281		62,857,531
Bank Rakyat Indonesia		170,058,000		49,663,218
HDFC Bank Ltd.		5,174,923		85,110,807
Intesa Sanpaolo S.p.A.		52,151,489		126,996,963
Julius Baer Group Ltd.		2,317,796		97,368,556
KBC Group N.V.		1,522,249		101,378,441
Mastercard, Inc., “A”		249,922		72,539,861

			$	674,293,296
Pharmaceuticals - 8.8%
Bayer AG		1,931,026	$	139,803,788
Kyowa Kirin Co. Ltd.		2,433,100		57,725,270
Novo Nordisk A.S., “B”		3,559,579		211,558,126
Roche Holding AG		986,771		321,632,564
Santen Pharmaceutical Co. Ltd.		8,758,300		140,639,492

			$	871,359,240
Printing & Publishing - 1.8%
RELX PLC		2,503,095	$	60,575,693
Wolters Kluwer N.V.		1,566,782		115,154,151

			$	175,729,844
Real Estate - 2.7%
Grand City Properties S.A.		5,912,042	$	138,584,740
LEG Immobilien AG		1,081,979		129,287,352

			$	267,872,092
Restaurants - 0.7%
Yum China Holdings, Inc.		1,562,334	$	68,414,606

Specialty Chemicals - 8.4%
Akzo Nobel N.V.		1,514,512	$	121,590,144
Croda International PLC		1,902,532		111,565,707

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued

Specialty Chemicals - continued
Kansai Paint Co. Ltd.		2,362,900	$	51,445,125
Linde PLC		1,229,712		232,844,260
Nitto Denko Corp.		1,384,000		69,007,881
Sika AG		677,900		121,116,614
Symrise AG		1,185,490		115,465,519

			$	823,035,250
Specialty Stores - 0.2%
Dufry AG		214,632	$	15,698,968

Telecommunications - Wireless - 3.4%
Advanced Info Service Public Co. Ltd.		8,297,700	$	52,854,942
KDDI Corp.		3,856,700		108,991,839
SoftBank Corp.		2,520,600		116,125,354
Tele2 AB, “B”		4,077,603		59,357,296

			$	337,329,431
Telephone Services - 0.6%
Hellenic Telecommunications Organization S.A.		3,933,166	$	55,814,091

Tobacco - 2.1%
British American Tobacco PLC		3,597,177	$	142,951,022
Japan Tobacco, Inc.		3,220,000		63,857,376

			$	206,808,398
Trucking - 0.3%
Yamato Holdings Co. Ltd.		2,121,000	$	33,289,884

Utilities - Electric Power - 2.8%
CLP Holdings Ltd.		8,055,500	$	84,879,743
Iberdrola S.A.		12,574,243		143,920,389
Orsted A.S.		493,048		50,737,531

			$	279,537,663
Total Common Stocks (Identified Cost, $8,964,411,043)			$	9,768,843,694

Investment Companies (h) - 0.7%
Money Market Funds - 0.7%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $71,008,132)		71,012,329	$	71,019,430

Other Assets, Less Liabilities - 0.2%			15,860,636
Net Assets - 100.0%			$	9,855,723,760

Portfolio of Investments (unaudited) – continued

(a)	Non-income producing security.

(h)

(l)	A portion of this security is on loan. See Note 2 for additional information.

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

ADR

American Depositary Receipt

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value, including $2,202,728 of securities on loan (identified cost, $8,964,411,043)			$9,768,843,694
Investments in affiliated issuers, at value (identified cost, $71,008,132)			71,019,430
Cash			432,577
Foreign currency, at value (identified cost, $3,733,341)			3,757,842
Receivables for
Investments sold			17,049,739
Fund shares sold			50,159,093
Interest and dividends			34,873,661
Other assets			26,203
Total assets			$9,946,162,239

Liabilities
Payables for
Investments purchased			$62,685,582
Fund shares reacquired			23,983,023
Payable to affiliates
Investment adviser			547,688
Administrative services fee			4,666
Shareholder servicing costs			793,797
Distribution and service fees			19,580
Program manager fees			63
Payable for independent Trustees’ compensation			6,912
Deferred country tax expense payable			1,611,728
Accrued expenses and other liabilities			785,440
Total liabilities			$90,438,479
Net assets			$9,855,723,760

Net assets consist of
Paid-in capital			$9,201,814,582
Total distributable earnings (loss)			653,909,178
Net assets			$9,855,723,760
Shares of beneficial interest outstanding			547,598,736

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$641,444,251		35,503,574		$18.07
Class B		2,900,597		165,978		17.48
Class C		20,832,831		1,224,513		17.01
Class I		691,407,435		36,918,852		18.73
Class R1		1,769,129		106,229		16.65
Class R2		90,302,571		5,176,756		17.44
Class R3		60,638,002		3,392,105		17.88
Class R4		35,038,865		1,935,991		18.10
Class R6		8,296,350,894		462,310,763		17.95
Class 529A		11,973,101		676,614		17.70
Class 529B		253,203		15,175		16.69
Class 529C		2,812,881		172,186		16.34

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Classes A and 529A, for which the maximum offering prices per share were $19.17 [100 / 94.25 x $18.07] and $18.78 [100 / 94.25 x $17.70], respectively. On sales of $50,000 or more, the maximum offering prices of Class A and Class 529A shares are reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, Class C, Class 529B, and Class 529C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, R6, and 529A.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$68,046,082
Dividends from affiliated issuers	981,476
Other	53,589
Income on securities loaned	5,912
Interest	14
Foreign taxes withheld	(5,669,027	)
Total investment income	$63,418,046
Expenses
Management fee	$33,422,046
Distribution and service fees	1,341,924
Shareholder servicing costs	941,960
Program manager fees	3,976
Administrative services fee	275,671
Independent Trustees’ compensation	50,523
Custodian fee	652,830
Shareholder communications	111,465
Audit and tax fees	36,341
Legal fees	36,824
Miscellaneous	175,136
Total expenses	$37,048,696
Reduction of expenses by investment adviser and distributor	(505,162	)
Net expenses	$36,543,534
Net investment income (loss)	$26,874,512

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers (net of $165,944 country tax)	$87,667,271
Affiliated issuers	102
Foreign currency	(203,565	)
Net realized gain (loss)	$87,463,808
Change in unrealized appreciation or depreciation
Unaffiliated issuers (net of $1,026,530 decrease in deferred country tax)	$90,387,118
Affiliated issuers	(223	)
Translation of assets and liabilities in foreign currencies	413,160
Net unrealized gain (loss)	$90,800,055
Net realized and unrealized gain (loss)	$178,263,863
Change in net assets from operations	$205,138,375

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$26,874,512			$173,044,547
Net realized gain (loss)		87,463,808			(159,620,089	)
Net unrealized gain (loss)		90,800,055			(109,450,837	)
Change in net assets from operations		$205,138,375			$(96,026,379	)
Total distributions to shareholders		$(195,001,414	)		$(399,506,930	)
Change in net assets from fund share transactions		$1,021,744,409			$904,797,447
Total change in net assets		$1,031,881,370			$409,264,138

Net assets
At beginning of period		8,823,842,390			8,414,578,252
At end of period		$9,855,723,760			$8,823,842,390

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.89			$19.19			$18.16			$15.83			$16.34			$18.06

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.32			$0.26			$0.20	(c)		$0.25			$0.26
Net realized and unrealized gain (loss)		0.48			(0.77	)		0.97			2.39			(0.50	)		(1.60	)
Total from investment operations		$0.50			$(0.45	)		$1.23			$2.59			$(0.25	)		$(1.34	)

Less distributions declared to shareholders
From net investment income		$(0.32	)		$(0.72	)		$(0.20	)		$(0.26	)		$(0.26	)		$(0.38	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.32	)		$(0.85	)		$(0.20	)		$(0.26	)		$(0.26	)		$(0.38	)
Net asset value, end of period (x)		$18.07			$17.89			$19.19			$18.16			$15.83			$16.34
Total return (%) (r)(s)(t)(x)		2.71	(n)		(1.82	)		6.79			16.66	(c)		(1.50	)		(7.44	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.07	(a)		1.10			1.09			1.12	(c)		1.14			1.13
Expenses after expense reductions (f)		1.05	(a)		1.09			1.08			1.10	(c)		1.11			1.09
Net investment income (loss)		0.25	(a)(l)		1.79			1.37			1.25	(c)		1.62			1.53
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$641,444			$622,639			$686,128			$693,538			$971,630			$1,178,013

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.23			$18.48			$17.48			$15.21			$15.65			$17.26

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.04	)		$0.16			$0.10			$0.10	(c)		$0.12			$0.12
Net realized and unrealized gain (loss)		0.46			(0.72	)		0.95			2.28			(0.47	)		(1.52	)
Total from investment operations		$0.42			$(0.56	)		$1.05			$2.38			$(0.35	)		$(1.40	)

Less distributions declared to shareholders
From net investment income		$(0.17	)		$(0.56	)		$(0.05	)		$(0.11	)		$(0.09	)		$(0.21	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.17	)		$(0.69	)		$(0.05	)		$(0.11	)		$(0.09	)		$(0.21	)
Net asset value, end of period (x)		$17.48			$17.23			$18.48			$17.48			$15.21			$15.65
Total return (%) (r)(s)(t)(x)		2.37	(n)		(2.63	)		6.01			15.77	(c)		(2.20	)		(8.15	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.82	(a)		1.85			1.84			1.87	(c)		1.89			1.88
Expenses after expense reductions (f)		1.81	(a)		1.84			1.82			1.85	(c)		1.86			1.84
Net investment income (loss)		(0.48	)(a)(l)		0.97			0.55			0.61	(c)		0.82			0.70
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$2,901			$3,347			$4,922			$6,228			$7,967			$11,228

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.79			$17.99			$17.03			$14.85			$15.31			$16.93

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.04	)		$0.17			$0.08			$0.10	(c)		$0.12			$0.12
Net realized and unrealized gain (loss)		0.43			(0.70	)		0.94			2.21			(0.45	)		(1.50	)
Total from investment operations		$0.39			$(0.53	)		$1.02			$2.31			$(0.33	)		$(1.38	)

Less distributions declared to shareholders
From net investment income		$(0.17	)		$(0.54	)		$(0.06	)		$(0.13	)		$(0.13	)		$(0.24	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.17	)		$(0.67	)		$(0.06	)		$(0.13	)		$(0.13	)		$(0.24	)
Net asset value, end of period (x)		$17.01			$16.79			$17.99			$17.03			$14.85			$15.31
Total return (%) (r)(s)(t)(x)		2.29	(n)		(2.56	)		5.97			15.74	(c)		(2.16	)		(8.17	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.82	(a)		1.85			1.84			1.87	(c)		1.89			1.88
Expenses after expense reductions (f)		1.81	(a)		1.84			1.83			1.85	(c)		1.86			1.84
Net investment income (loss)		(0.48	)(a)(l)		1.05			0.44			0.64	(c)		0.85			0.76
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$20,833			$22,825			$27,800			$48,570			$62,124			$77,442

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$18.55			$19.87			$18.79			$16.38			$16.90			$18.66

Income (loss) from investment operations
Net investment income (loss) (d)		$0.05			$0.37			$0.26			$0.30	(c)		$0.30			$0.32
Net realized and unrealized gain (loss)		0.50			(0.80	)		1.06			2.42			(0.51	)		(1.66	)
Total from investment operations		$0.55			$(0.43	)		$1.32			$2.72			$(0.21	)		$(1.34	)

Less distributions declared to shareholders
From net investment income		$(0.37	)		$(0.76	)		$(0.24	)		$(0.31	)		$(0.31	)		$(0.42	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.37	)		$(0.89	)		$(0.24	)		$(0.31	)		$(0.31	)		$(0.42	)
Net asset value, end of period (x)		$18.73			$18.55			$19.87			$18.79			$16.38			$16.90
Total return (%) (r)(s)(t)(x)		2.84	(n)		(1.61	)		7.05			16.95	(c)		(1.24	)		(7.19	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.82	(a)		0.85			0.84			0.87	(c)		0.89			0.88
Expenses after expense reductions (f)		0.81	(a)		0.84			0.83			0.86	(c)		0.86			0.84
Net investment income (loss)		0.50	(a)(l)		2.03			1.31			1.79	(c)		1.86			1.80
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$691,407			$593,064			$658,193			$1,099,134			$2,187,011			$2,410,936

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.46			$17.72			$16.80			$14.63			$15.08			$16.69

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.04	)		$0.15			$0.11			$0.09	(c)		$0.11			$0.11
Net realized and unrealized gain (loss)		0.44			(0.69	)		0.90			2.20			(0.44	)		(1.47	)
Total from investment operations		$0.40			$(0.54	)		$1.01			$2.29			$(0.33	)		$(1.36	)

Less distributions declared to shareholders
From net investment income		$(0.21	)		$(0.59	)		$(0.09	)		$(0.12	)		$(0.12	)		$(0.25	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.21	)		$(0.72	)		$(0.09	)		$(0.12	)		$(0.12	)		$(0.25	)
Net asset value, end of period (x)		$16.65			$16.46			$17.72			$16.80			$14.63			$15.08
Total return (%) (r)(s)(t)(x)		2.34	(n)		(2.62	)		5.99			15.79	(c)		(2.19	)		(8.18	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.82	(a)		1.85			1.84			1.87	(c)		1.89			1.88
Expenses after expense reductions (f)		1.81	(a)		1.84			1.83			1.85	(c)		1.86			1.84
Net investment income (loss)		(0.50	)(a)(l)		0.95			0.60			0.61	(c)		0.78			0.72
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$1,769			$1,751			$2,153			$2,089			$2,418			$3,509

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.25			$18.53			$17.55			$15.31			$15.80			$17.48

Income (loss) from investment operations
Net investment income (loss) (d)		$0.00	(w)		$0.26			$0.19			$0.17	(c)		$0.21			$0.22
Net realized and unrealized gain (loss)		0.46			(0.75	)		0.95			2.30			(0.48	)		(1.56	)
Total from investment operations		$0.46			$(0.49	)		$1.14			$2.47			$(0.27	)		$(1.34	)

Less distributions declared to shareholders
From net investment income		$(0.27	)		$(0.66	)		$(0.16	)		$(0.23	)		$(0.22	)		$(0.34	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.27	)		$(0.79	)		$(0.16	)		$(0.23	)		$(0.22	)		$(0.34	)
Net asset value, end of period (x)		$17.44			$17.25			$18.53			$17.55			$15.31			$15.80
Total return (%) (r)(s)(t)(x)		2.60	(n)		(2.14	)		6.49			16.37	(c)		(1.69	)		(7.69	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.32	(a)		1.35			1.34			1.37	(c)		1.39			1.38
Expenses after expense reductions (f)		1.30	(a)		1.34			1.33			1.35	(c)		1.36			1.34
Net investment income (loss)		0.02	(a)(l)		1.51			1.04			1.10	(c)		1.38			1.29
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$90,303			$98,935			$121,197			$132,988			$152,133			$169,812

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.70			$18.99			$17.98			$15.67			$16.16			$17.86

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.30			$0.25			$0.22	(c)		$0.24			$0.25
Net realized and unrealized gain (loss)		0.48			(0.75	)		0.96			2.35			(0.48	)		(1.58	)
Total from investment operations		$0.50			$(0.45	)		$1.21			$2.57			$(0.24	)		$(1.33	)

Less distributions declared to shareholders
From net investment income		$(0.32	)		$(0.71	)		$(0.20	)		$(0.26	)		$(0.25	)		$(0.37	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.32	)		$(0.84	)		$(0.20	)		$(0.26	)		$(0.25	)		$(0.37	)
Net asset value, end of period (x)		$17.88			$17.70			$18.99			$17.98			$15.67			$16.16
Total return (%) (r)(s)(t)(x)		2.72	(n)		(1.83	)		6.75			16.67	(c)		(1.47	)		(7.44	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.07	(a)		1.10			1.09			1.12	(c)		1.14			1.13
Expenses after expense reductions (f)		1.06	(a)		1.09			1.08			1.10	(c)		1.11			1.09
Net investment income (loss)		0.25	(a)(l)		1.73			1.31			1.37	(c)		1.59			1.46
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$60,638			$61,214			$82,289			$91,653			$126,980			$165,656

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.93			$19.25			$18.21			$15.86			$16.36			$18.09

Income (loss) from investment operations
Net investment income (loss) (d)		$0.06			$0.36			$0.30			$0.28	(c)		$0.30			$0.29
Net realized and unrealized gain (loss)		0.47			(0.78	)		0.98			2.35			(0.50	)		(1.60	)
Total from investment operations		$0.53			$(0.42	)		$1.28			$2.63			$(0.20	)		$(1.31	)

Less distributions declared to shareholders
From net investment income		$(0.36	)		$(0.77	)		$(0.24	)		$(0.28	)		$(0.30	)		$(0.42	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.36	)		$(0.90	)		$(0.24	)		$(0.28	)		$(0.30	)		$(0.42	)
Net asset value, end of period (x)		$18.10			$17.93			$19.25			$18.21			$15.86			$16.36
Total return (%) (r)(s)(t)(x)		2.84	(n)		(1.65	)		7.07			16.92	(c)		(1.20	)		(7.26	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.82	(a)		0.85			0.84			0.87	(c)		0.89			0.88
Expenses after expense reductions (f)		0.81	(a)		0.84			0.83			0.86	(c)		0.86			0.85
Net investment income (loss)		0.61	(a)(l)		2.04			1.57			1.73	(c)		1.93			1.70
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$35,039			$54,352			$58,578			$63,884			$148,243			$343,475

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.80			$19.11			$18.10			$15.79			$16.30			$18.02

Income (loss) from investment operations
Net investment income (loss) (d)		$0.06			$0.38			$0.34			$0.28	(c)		$0.31			$0.32
Net realized and unrealized gain (loss)		0.48			(0.77	)		0.95			2.36			(0.50	)		(1.60	)
Total from investment operations		$0.54			$(0.39	)		$1.29			$2.64			$(0.19	)		$(1.28	)

Less distributions declared to shareholders
From net investment income		$(0.39	)		$(0.79	)		$(0.28	)		$(0.33	)		$(0.32	)		$(0.44	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.39	)		$(0.92	)		$(0.28	)		$(0.33	)		$(0.32	)		$(0.44	)
Net asset value, end of period (x)		$17.95			$17.80			$19.11			$18.10			$15.79			$16.30
Total return (%) (r)(s)(t)(x)		2.91	(n)		(1.48	)		7.12			17.07	(c)		(1.13	)		(7.13	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.71	(a)		0.74			0.74			0.77	(c)		0.79			0.79
Expenses after expense reductions (f)		0.70	(a)		0.73			0.73			0.76	(c)		0.76			0.75
Net investment income (loss)		0.59	(a)(l)		2.18			1.80			1.72	(c)		2.02			1.88
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$8,296,351			$7,350,641			$6,756,773			$5,228,377			$2,766,544			$3,010,863

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$17.52			$18.83			$17.84			$15.61			$16.12			$17.81

Income (loss) from investment operations
Net investment income (loss) (d)		$0.02			$0.31			$0.26			$0.23	(c)		$0.19			$0.26
Net realized and unrealized gain (loss)		0.48			(0.77	)		0.95			2.31			(0.44	)		(1.58	)
Total from investment operations		$0.50			$(0.46	)		$1.21			$2.54			$(0.25	)		$(1.32	)

Less distributions declared to shareholders
From net investment income		$(0.32	)		$(0.72	)		$(0.22	)		$(0.31	)		$(0.26	)		$(0.37	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.32	)		$(0.85	)		$(0.22	)		$(0.31	)		$(0.26	)		$(0.37	)
Net asset value, end of period (x)		$17.70			$17.52			$18.83			$17.84			$15.61			$16.12
Total return (%) (r)(s)(t)(x)		2.74	(n)		(1.94	)		6.78			16.60	(c)		(1.52	)		(7.43	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.12	(a)		1.15			1.15			1.22	(c)		1.23			1.23
Expenses after expense reductions (f)		1.09	(a)		1.13			1.11			1.13	(c)		1.13			1.12
Net investment income (loss)		0.22	(a)(l)		1.77			1.37			1.39	(c)		1.22			1.51
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$11,973			$11,805			$12,615			$10,464			$9,101			$2,419

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.47			$17.72			$16.79			$14.78			$15.19			$16.80

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.05	)		$0.16			$0.10			$0.09	(c)		$0.05			$0.10
Net realized and unrealized gain (loss)		0.45			(0.71	)		0.90			2.18			(0.39	)		(1.47	)
Total from investment operations		$0.40			$(0.55	)		$1.00			$2.27			$(0.34	)		$(1.37	)

Less distributions declared to shareholders
From net investment income		$(0.18	)		$(0.57	)		$(0.07	)		$(0.26	)		$(0.07	)		$(0.24	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.18	)		$(0.70	)		$(0.07	)		$(0.26	)		$(0.07	)		$(0.24	)
Net asset value, end of period (x)		$16.69			$16.47			$17.72			$16.79			$14.78			$15.19
Total return (%) (r)(s)(t)(x)		2.36	(n)		(2.64	)		5.94			15.68	(c)		(2.25	)		(8.17	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.87	(a)		1.90			1.90			1.97	(c)		1.98			1.98
Expenses after expense reductions (f)		1.85	(a)		1.89			1.88			1.90	(c)		1.90			1.89
Net investment income (loss)		(0.53	)(a)(l)		1.00			0.56			0.58	(c)		0.37			0.63
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$253			$287			$358			$386			$434			$138

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$16.13			$17.38			$16.51			$14.53			$15.01			$16.61

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.05	)		$0.15			$0.09			$0.10	(c)		$0.07			$0.11
Net realized and unrealized gain (loss)		0.44			(0.69	)		0.89			2.15			(0.41	)		(1.46	)
Total from investment operations		$0.39			$(0.54	)		$0.98	��		$2.25			$(0.34	)		$(1.35	)

Less distributions declared to shareholders
From net investment income		$(0.18	)		$(0.58	)		$(0.11	)		$(0.27	)		$(0.14	)		$(0.25	)
From net realized gain		—			(0.13	)		—			—			—			—
Total distributions declared to shareholders		$(0.18	)		$(0.71	)		$(0.11	)		$(0.27	)		$(0.14	)		$(0.25	)
Net asset value, end of period (x)		$16.34			$16.13			$17.38			$16.51			$14.53			$15.01
Total return (%) (r)(s)(t)(x)		2.36	(n)		(2.68	)		5.93			15.78(	c)		(2.28	)		(8.17	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.87	(a)		1.90			1.90			1.97	(c)		1.99			1.98
Expenses after expense reductions (f)		1.85	(a)		1.89			1.87			1.89	(c)		1.90			1.89
Net investment income (loss)		(0.52	)(a)(l)		0.95			0.53			0.63	(c)		0.47			0.72
Portfolio turnover		8	(n)		22			25			33			40			28
Net assets at end of period (000 omitted)		$2,813			$2,981			$3,572			$3,856			$3,298			$980

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(l)	Recognition of net investment income by the fund may be affected by the timing of the declaration of dividends by companies in which the fund invests and the actual annual net investment income ratio may differ.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(w)	Per share amount was less than $0.01.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Research International Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

General– The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued. The fund invests in foreign securities. Investments in foreign securities are vulnerable to the effects of changes in the relative values of the local currency and the U.S. dollar and to the effects of changes in each country’s market, economic, industrial, political, regulatory, geopolitical, and other conditions.

Notes to Financial Statements (unaudited) – continued

Investment Valuations– Equity securities, including restricted equity securities, are generally valued at the last sale or official closing price on their primary market or exchange as provided by a third-party pricing service. Equity securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

Notes to Financial Statements (unaudited) – continued



Financial Instruments	Level 1		Level 2		Level 3		Total
Equity Securities:
Japan		$140,639,492		$1,809,290,329		$—		$1,949,929,821
Switzerland		—		1,369,054,243		—		1,369,054,243
France		—		1,174,854,240		—		1,174,854,240
Germany		—		752,480,484		—		752,480,484
United Kingdom		—		736,194,522		—		736,194,522
United States		377,722,308		232,844,260		—		610,566,568
Hong Kong		—		472,466,696		—		472,466,696
Netherlands		51,357,866		236,744,295		—		288,102,161
Spain		—		286,192,874		—		286,192,874
Other Countries		583,904,870		1,545,097,215		—		2,129,002,085
Mutual Funds		71,019,430		—		—		71,019,430
Total		$1,224,643,966		$8,615,219,158		$—		$9,839,863,124

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

cash and/or U.S. Treasury and federal agency obligations in an amount typically at least equal to the market value of the securities loaned. On loans collateralized by cash, the cash collateral is invested in a money market fund. The market value of the loaned securities is determined at the close of business of the fund and any additional required collateral is delivered to the fund on the next business day. The lending agent provides the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. At period end, the fund had investment securities on loan, all of which were classified as equity securities in the fund’s Portfolio of Investments, with a fair value of $2,202,728. The fair value of the fund’s investment securities on loan is presented gross in the Statement of Assets and Liabilities. These loans were collateralized by U.S. Treasury Obligations of $2,271,278 held by the lending agent. The collateral on securities loaned exceeded the value of securities on loan at period end. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income.

Investment Transactions and Income– Investment transactions are recorded on the trade date. Interest income is recorded on the accrual basis. Dividends received in cash are recorded on theex-dividend date. Certain dividends from foreign securities will be recorded when the fund is informed of the dividend if such information is obtained subsequent to theex-dividend date. Dividend and interest payments received in additional securities are recorded on theex-dividend orex-interest date in an amount equal to the value of the security on such date.

Notes to Financial Statements (unaudited) – continued

Book/tax differences primarily relate to passive foreign investment companies and wash sale loss deferrals.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$342,429,321
Long-term capital gains		57,077,609

Total distributions		$399,506,930

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$9,100,517,473
Gross appreciation	1,481,140,936

Gross depreciation	(741,795,285	)
Net unrealized appreciation (depreciation)	$739,345,651

As of 8/31/19

Undistributed ordinary income	161,295,878
Post-October capital loss deferral	(163,984,198	)
Other temporary differences	(886,491	)
Net unrealized appreciation (depreciation)	647,347,028

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.

Notes to Financial Statements (unaudited) – continued

Multiple Classes of Shares of Beneficial Interest– The fund offers multiple classes of shares, which differ in their respective distribution, service, and program manager fees. The fund’s income, realized and unrealized gain (loss), and common expenses are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B and Class 529B shares will convert to Class A and Class 529A shares, respectively, approximately eight years after purchase. Class C and Class 529C shares will convert to Class A and Class 529A shares, respectively, approximately ten years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$11,396,463		$30,548,265
Class B		30,070		168,883
Class C		220,193		980,659
Class I		11,272,253		28,945,460
Class R1		22,306		84,285
Class R2		1,489,011		4,982,298
Class R3		1,090,789		3,381,859
Class R4		725,317		2,607,048
Class R6		168,508,766		327,097,188
Class 529A		212,373		556,856
Class 529B		3,033		13,781
Class 529C		30,840		140,348
Total		$195,001,414		$399,506,930

(3) Transactions with Affiliates


Up to $1 billion	0.90	%
In excess of $1 billion and up to $2 billion	0.80	%
In excess of $2 billion and up to $5 billion	0.70	%
In excess of $5 billion and up to $10 billion	0.60	%
In excess of $10 billion and up to $20 billion	0.55	%
In excess of $20 billion	0.50	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $498,271, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.67% of the fund’s average daily net assets.

Notes to Financial Statements (unaudited) – continued

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $40,853 and $3,022 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A and Class 529A shares of the fund, respectively.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.25%		$835,930
Class B		0.75%		0.25%		1.00%		1.00%		16,608
Class C		0.75%		0.25%		1.00%		1.00%		114,372
Class R1		0.75%		0.25%		1.00%		1.00%		9,420
Class R2		0.25%		0.25%		0.50%		0.50%		251,646
Class R3		—		0.25%		0.25%		0.25%		81,667
Class 529A		—		0.25%		0.25%		0.23%		15,748
Class 529B		0.75%		0.25%		1.00%		1.00%		1,465
Class 529C		0.75%		0.25%		1.00%		0.99%		15,068
Total Distribution and Service Fees										$1,341,924

(d)

(e)

The annual effective rates represent actual fees incurred under the distribution plan for the six months ended February 29, 2020 based on each class’s average daily net assets. MFD has voluntarily agreed to rebate a portion of each class’s 0.25% service fee attributable to accounts for which MFD retains the 0.25% service fee except for accounts attributable to MFS or its affiliates’ seed money. For the six months ended February 29, 2020, this rebate amounted to $5,176, $1, $44, $433, $1,133, $3, and $101 for Class A, Class B, Class C, Class R2, Class 529A, Class 529B, and Class 529C, respectively, and is included in the reduction of total expenses in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the six months ended February 29, 2020, were as follows:



	Amount
Class A		$855
Class B		2,201
Class C		643
Class 529B		5
Class 529C		36

The fund has entered into and may from time to time enter into contracts with program managers and other parties which administer the tuition programs through which an investment in the fund’s 529 share classes is made. The fund has entered into an agreement with MFD pursuant to which MFD receives an annual fee of up to 0.05% of the average daily net assets attributable to each 529 share class. The services provided by MFD, or a third party with which MFD contracts, include recordkeeping and tax reporting and account services, as well as services designed to maintain the program’s compliance with the Internal Revenue Code and other regulatory requirements. Program manager fees for the six months ended February 29, 2020, were as follows:



	Fee
Class 529A		$3,150
Class 529B		73
Class 529C		753

Total Program Manager Fees		$3,976

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $60,388, which equated to 0.0012% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $881,572.

Notes to Financial Statements (unaudited) – continued

compensation directly to Trustees or officers of the fund who are also officers of the investment adviser, all of whom receive remuneration from MFS for their services to the fund. Certain officers and Trustees of the fund are officers or directors of MFS, MFD, and MFSC.

The fund is permitted to engage in purchase and sale transactions with funds and accounts for which MFS serves as investment adviser orsub-adviser (“cross-trades”) pursuant to a policy adopted by the Board of Trustees. This policy has been designed to ensure that cross-trades conducted by the fund comply with Rule17a-7 under the Investment Company Act of 1940. During the six months ended February 29, 2020, the fund engaged in purchase and sale transactions pursuant to this policy, which amounted to $8,347,414 and $720,279, respectively. The sales transactions resulted in net realized gains (losses) of $296,037.

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short-term obligations, aggregated $1,610,081,059 and $725,323,616, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20				Year ended 8/31/19

	Shares		Amount		Shares		Amount
Shares sold
Class A		4,782,829		$91,700,612		6,308,181		$108,057,448
Class B		319		6,125		6,034		99,733
Class C		58,819		1,059,812		376,118		5,774,726
Class I		10,147,493		200,992,100		10,627,716		191,924,273
Class R1		5,313		93,830		11,118		182,062
Class R2		275,364		5,091,529		671,662		11,368,179
Class R3		636,318		11,909,205		431,846		7,494,227
Class R4		150,064		2,876,246		550,567		9,576,959
Class R6		53,977,313		1,034,090,815		108,922,349		1,895,362,745
Class 529A		37,599		709,982		87,876		1,489,187
Class 529B		266		4,879		805		12,865
Class 529C		10,266		179,641		17,370		275,909
		70,081,963		$1,348,714,776		128,011,642		$2,231,618,313

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares issued to shareholders in reinvestment of distributions
Class A		437,195			$8,359,174			1,384,970			$22,173,336
Class B		1,242			23,006			8,845			137,183
Class C		9,214			166,220			44,618			674,185
Class I		442,527			8,766,464			1,213,492			20,107,565
Class R1		1,263			22,306			5,660			83,875
Class R2		79,497			1,469,099			310,892			4,809,494
Class R3		57,653			1,090,789			213,501			3,381,859
Class R4		37,248			713,292			160,956			2,578,518
Class R6		8,352,804			158,536,225			19,346,528			307,416,337
Class 529A		11,339			212,373			35,487			556,785
Class 529B		171			3,033			929			13,781
Class 529C		1,781			30,840			9,666			140,348
		9,431,934			$179,392,821			22,735,544			$362,073,266

Shares reacquired
Class A		(4,528,758	)		$(86,542,868	)		(8,627,351	)		$(149,525,414	)
Class B		(29,801	)		(552,777	)		(87,072	)		(1,469,628	)
Class C		(203,311	)		(3,643,644	)		(606,008	)		(9,833,848	)
Class I		(5,648,662	)		(111,273,452	)		(12,990,232	)		(235,108,050	)
Class R1		(6,708	)		(120,273	)		(31,884	)		(499,317	)
Class R2		(911,857	)		(16,886,904	)		(1,789,045	)		(30,140,366	)
Class R3		(760,915	)		(14,331,282	)		(1,518,596	)		(26,270,828	)
Class R4		(1,282,732	)		(24,348,812	)		(723,854	)		(12,619,137	)
Class R6		(13,023,849	)		(247,322,894	)		(68,790,407	)		(1,220,513,670	)
Class 529A		(46,080	)		(869,328	)		(119,736	)		(2,083,794	)
Class 529B		(2,696	)		(48,890	)		(4,495	)		(74,302	)
Class 529C		(24,634	)		(422,064	)		(47,818	)		(755,778	)
		(26,470,003	)		$(506,363,188	)		(95,336,498	)		$(1,688,894,132	)

Net change
Class A		691,266			$13,516,918			(934,200	)		$(19,294,630	)
Class B		(28,240	)		(523,646	)		(72,193	)		(1,232,712	)
Class C		(135,278	)		(2,417,612	)		(185,272	)		(3,384,937	)
Class I		4,941,358			98,485,112			(1,149,024	)		(23,076,212	)
Class R1		(132	)		(4,137	)		(15,106	)		(233,380	)
Class R2		(556,996	)		(10,326,276	)		(806,491	)		(13,962,693	)
Class R3		(66,944	)		(1,331,288	)		(873,249	)		(15,394,742	)
Class R4		(1,095,420	)		(20,759,274	)		(12,331	)		(463,660	)
Class R6		49,306,268			945,304,146			59,478,470			982,265,412
Class 529A		2,858			53,027			3,627			(37,822	)
Class 529B		(2,259	)		(40,978	)		(2,761	)		(47,656	)
Class 529C		(12,587	)		(211,583	)		(20,782	)		(339,521	)
		53,043,894			$1,021,744,409			55,410,688			$904,797,447

Notes to Financial Statements (unaudited) – continued

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B and Class 529B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

The fund is one of several mutual funds in which certain MFS funds may invest. The MFS funds do not invest in the underlying funds for the purpose of exercising management or control. At the end of the period, the MFS International Diversification Fund, the MFS Growth Allocation Fund, the MFS Moderate Allocation Fund, the MFS Aggressive Growth Allocation Fund, and the MFS Conservative Allocation Fund were the owners of record of approximately 64%, 4%, 3%, 2%, and 1%, respectively, of the value of outstanding voting shares of the fund. In addition, the MFS Lifetime 2020 Fund, the MFS Lifetime 2025 Fund, the MFS Lifetime 2030 Fund, the MFS Lifetime 2035 Fund, the MFS Lifetime 2040 Fund, the MFS Lifetime 2045 Fund, the MFS Lifetime 2050 Fund, the MFS Lifetime 2055 Fund, the MFS Lifetime 2060 Fund, and the MFS Lifetime Income Fund were each the owners of record of less than 1% of the value of outstanding voting shares of the fund.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $23,187 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)		Change in Unrealized Appreciation or Depreciation			Ending Value
MFS Institutional Money Market Portfolio		$73,245,985		$944,005,814		$946,232,248		$102		$(223	)		$71,019,430

Affiliated Issuers									Dividend Income			Capital Gain Distributions
MFS Institutional Money Market Portfolio										$981,476			$—

Notes to Financial Statements (unaudited) – continued

(8) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

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Semiannual Report

February 29, 2020

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MFS® Technology Fund

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SCT-SEM

MFS® Technology Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			5
Statement of assets and liabilities			8
Statement of operations			10
Statements of changes in net assets			11
Financial highlights			12
Notes to financial statements			21
Proxy voting policies and information			34
Quarterly portfolio disclosure			34
Further information			34
Information about fund contracts and legal claims			34
Provision of financial reports and summary prospectuses			34


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

LOGO

LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

LOGO


Top ten holdings
Amazon.com, Inc.			9.4%
Microsoft Corp.			7.8%
Alphabet, Inc., “A”			7.4%
Facebook, Inc., “A”			6.5%
Visa, Inc., “A”			4.9%
Mastercard, Inc., “A”			4.5%
Adobe Systems, Inc.			4.2%
Salesforce.com, Inc.			3.5%
Global Payments, Inc.			3.5%
Fiserv, Inc.			3.2%


Top five industries
Computer Software			21.4%
Internet			16.1%
Business Services			15.2%
Computer Software - Systems			10.6%
Specialty Stores			10.0%

(s)	Includes securities sold short.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		1.18%		$1,000.00		$1,071.15		$6.08
A	Hypothetical (h)		1.18%		$1,000.00		$1,019.00		$5.92
B	Actual		1.93%		$1,000.00		$1,066.84		$9.92
B	Hypothetical (h)		1.93%		$1,000.00		$1,015.27		$9.67
C	Actual		1.93%		$1,000.00		$1,067.27		$9.92
C	Hypothetical (h)		1.93%		$1,000.00		$1,015.27		$9.67
I	Actual		0.93%		$1,000.00		$1,072.32		$4.79
I	Hypothetical (h)		0.93%		$1,000.00		$1,020.24		$4.67
R1	Actual		1.93%		$1,000.00		$1,067.14		$9.92
R1	Hypothetical (h)		1.93%		$1,000.00		$1,015.27		$9.67
R2	Actual		1.43%		$1,000.00		$1,069.78		$7.36
R2	Hypothetical (h)		1.43%		$1,000.00		$1,017.75		$7.17
R3	Actual		1.18%		$1,000.00		$1,070.96		$6.08
R3	Hypothetical (h)		1.18%		$1,000.00		$1,019.00		$5.92
R4	Actual		0.93%		$1,000.00		$1,072.42		$4.79
R4	Hypothetical (h)		0.93%		$1,000.00		$1,020.24		$4.67
R6	Actual		0.84%		$1,000.00		$1,072.83		$4.33
R6	Hypothetical (h)		0.84%		$1,000.00		$1,020.69		$4.22

(h)	5% class return per year before expenses.

(p)

Notes to Expense Table

Expense ratios include 0.05% of investment related expenses from short sales (See Note 2 of the Notes to Financial Statements).

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 97.8%
Aerospace - 1.6%
L3Harris Technologies, Inc.		56,492	$	11,170,163
Northrop Grumman Corp.		19,782		6,505,113
PAE, Inc. (a)		328,118		3,592,892

			$	21,268,168
Biotechnology - 1.5%
Adaptive Biotechnologies Corp. (a)		163,600	$	4,597,160
Bio-Techne Corp.		44,576		8,419,960
Illumina, Inc. (a)		24,449		6,495,366

			$	19,512,486
Brokerage & Asset Managers - 1.2%
NASDAQ, Inc.		90,113	$	9,241,088
Tradeweb Markets, Inc.		151,868		7,323,075

			$	16,564,163
Business Services - 15.2%
Clarivate Analytics PLC (a)		455,754	$	9,270,037
Endava PLC, ADR (a)		353,559		18,756,305
Equifax, Inc.		57,010		8,097,701
Fidelity National Information Services, Inc.		232,742		32,518,712
Fiserv, Inc. (a)		386,237		42,238,878
Global Payments, Inc.		251,835		46,330,091
PayPal Holdings, Inc. (a)		257,496		27,806,993
TransUnion		113,402		10,083,706
Verisk Analytics, Inc., “A”		54,703		8,484,982

			$	203,587,405
Cable TV - 0.8%
Charter Communications, Inc., “A” (a)		21,428	$	10,567,647

Computer Software - 21.4%
Adobe Systems, Inc. (a)		165,017	$	56,950,667
Autodesk, Inc. (a)		76,734		14,646,986
Black Knight, Inc. (a)		66,502		4,436,349
Blue Prism Group PLC (a)		400,847		7,431,658
DocuSign, Inc. (a)		118,090		10,192,348
Everbridge, Inc. (a)		20,448		2,160,536
Freee KK (a)		41,600		1,309,401
Microsoft Corp.		648,830		105,116,948
Rakus Co. Ltd.		503,100		7,185,679
RingCentral, Inc. (a)		70,673		16,661,160
Salesforce.com, Inc. (a)		274,713		46,811,095

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued

Computer Software - continued
Uber Technologies, Inc. (a)		182,224	$	6,171,927
Zendesk, Inc. (a)		97,088		7,700,049

			$	286,774,803
Computer Software - Systems - 10.6%
Apple, Inc.		141,714	$	38,738,939
Constellation Software, Inc.		12,856		13,097,173
Descartes Systems Group, Inc. (a)		178,676		7,418,598
EPAM Systems, Inc. (a)		29,857		6,664,082
HubSpot, Inc. (a)		77,448		13,898,044
OneConnect Financial Technology, ADR (a)		247,888		2,689,585
Pluralsight, Inc., “A” (a)		308,521		5,500,929
Q2 Holdings, Inc. (a)		92,833		6,996,823
ServiceNow, Inc. (a)		65,441		21,339,656
Square, Inc., “A” (a)		145,061		12,087,933
Wix.com Ltd. (a)		71,602		9,596,816
Workday, Inc. (a)		20,122		3,486,137

			$	141,514,715
Electrical Equipment - 0.9%
Amphenol Corp., “A”		128,123	$	11,746,317

Electronics - 4.7%
Applied Materials, Inc.		397,375	$	23,095,435
Marvell Technology Group Ltd.		423,926		9,029,624
Microchip Technology, Inc.		236,508		21,453,641
NXP Semiconductors N.V.		59,192		6,729,538
Silicon Laboratories, Inc. (a)		36,034		3,195,495

			$	63,503,733
Internet - 16.1%
Alibaba Group Holding Ltd., ADR (a)		45,297	$	9,421,776
Alphabet, Inc., “A” (a)(s)		74,314		99,525,024
Facebook, Inc., “A” (a)(s)		453,971		87,375,798
GoDaddy, Inc. (a)		177,673		12,433,557
Tencent Holdings Ltd.		148,400		7,319,890

			$	216,076,045
Leisure & Toys - 2.3%
Activision Blizzard, Inc.		192,044	$	11,163,518
Electronic Arts, Inc. (a)		195,050		19,772,218

			$	30,935,736
Medical & Health Technology & Services - 0.8%
Guardant Health, Inc. (a)		130,058	$	11,309,844

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par			Value ($)
Common Stocks - continued
Other Banks & Diversified Financials - 9.4%
Mastercard, Inc., “A”		206,338		$	59,889,604
Visa, Inc., “A”		359,896			65,414,697

				$	125,304,301
Printing & Publishing - 1.3%
IHS Markit Ltd.		136,136		$	9,698,329
Wolters Kluwer N.V.		109,867			8,074,921

				$	17,773,250
Specialty Stores - 10.0%
Amazon.com, Inc. (a)(s)		66,704		$	125,653,660
Chewy, Inc., “A” (a)		266,279			7,881,858

				$	133,535,518
Total Common Stocks (Identified Cost, $664,886,933)				$	1,309,974,131

Investment Companies (h) - 1.6%
Money Market Funds - 1.6%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $21,848,333)		21,847,725		$	21,849,909

Securities Sold Short - (0.0)%
Automotive - (0.0)%
Tesla, Inc. (Proceeds Received, $21,675)		(43	)	$	(28,723	)

Other Assets, Less Liabilities - 0.6%				8,514,717
Net Assets - 100.0%				$	1,340,310,034

(a)	Non-income producing security.

(h)

(s)	Security or a portion of the security was pledged to cover collateral requirements for securities sold short and/or certain derivative transactions.

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

ADR

American Depositary Receipt

At February 29, 2020, the fund had cash collateral of $13,344,290 and other liquid securities with an aggregate value of $26,445,245 to cover any collateral or margin obligations for securities sold short and certain derivative contracts. Restricted cash and/or deposits with brokers in the Statement of Assets and Liabilities are comprised of cash collateral.

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value (identified cost, $664,886,933)			$1,309,974,131
Investments in affiliated issuers, at value (identified cost, $21,848,333)			21,849,909
Deposits with brokers for
Securities sold short			13,344,290
Receivables for
Investments sold			4,671,785
Fund shares sold			13,880,676
Interest and dividends			679,173
Other assets			4,044
Total assets			$1,364,404,008

Liabilities
Payables for
Securities sold short, at value (proceeds received, $21,675)			$28,723
Investments purchased			1,350,344
Fund shares reacquired			22,023,641
Payable to affiliates
Investment adviser			80,512
Administrative services fee			1,545
Shareholder servicing costs			544,556
Distribution and service fees			25,706
Payable for independent Trustees’ compensation			2,018
Accrued expenses and other liabilities			36,929
Total liabilities			$24,093,974
Net assets			$1,340,310,034

Net assets consist of
Paid-in capital			$707,536,414
Total distributable earnings (loss)			632,773,620
Net assets			$1,340,310,034
Shares of beneficial interest outstanding			28,455,917

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$507,562,633		10,822,604		$46.90
Class B		38,774,296		976,603		39.70
Class C		132,558,043		3,346,141		39.62
Class I		327,105,598		6,479,431		50.48
Class R1		5,852,248		148,057		39.53
Class R2		29,076,569		654,907		44.40
Class R3		75,037,193		1,600,960		46.87
Class R4		25,966,516		528,991		49.09
Class R6		198,376,938		3,898,223		50.89

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Class A, for which the maximum offering price per share was $49.76 [100 / 94.25 x $46.90]. On sales of $50,000 or more, the maximum offering price of Class A shares is reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, and Class C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, and R6.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$2,613,163
Other	236,898
Dividends from affiliated issuers	219,588
Income on securities loaned	95,254
Foreign taxes withheld	(5,735	)
Total investment income	$3,159,168
Expenses
Management fee	$4,909,293
Distribution and service fees	1,692,117
Shareholder servicing costs	668,627
Administrative services fee	90,810
Independent Trustees’ compensation	12,524
Custodian fee	34,058
Shareholder communications	36,016
Audit and tax fees	30,299
Legal fees	5,369
Dividend and interest expense on securities sold short	312,631
Interest expense and fees	3,588
Miscellaneous	98,227
Total expenses	$7,893,559
Reduction of expenses by investment adviser and distributor	(79,672	)
Net expenses	$7,813,887
Net investment income (loss)	$(4,654,719	)

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$24,212,104
Affiliated issuers	4,624
Written options	606,271
Securities sold short	(19,439,014	)
Foreign currency	(3,895	)
Net realized gain (loss)	$5,380,090
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$90,614,945
Affiliated issuers	(4,218	)
Securities sold short	(2,009,410	)
Translation of assets and liabilities in foreign currencies	(46	)
Net unrealized gain (loss)	$88,601,271
Net realized and unrealized gain (loss)	$93,981,361
Change in net assets from operations	$89,326,642

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$(4,654,719	)		$(7,674,688	)
Net realized gain (loss)		5,380,090			30,801,602
Net unrealized gain (loss)		88,601,271			10,211,911
Change in net assets from operations		$89,326,642			$33,338,825
Total distributions to shareholders		$(27,686,049	)		$(51,440,197	)
Change in net assets from fund share transactions		$12,753,381			$47,069,408
Total change in net assets		$74,393,974			$28,968,036

Net assets
At beginning of period		1,265,916,060			1,236,948,024
At end of period		$1,340,310,034			$1,265,916,060

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$44.73			$45.65			$35.67			$28.27			$24.62			$24.47

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.16	)		$(0.27	)		$(0.26	)		$(0.19	)(c)		$(0.12	)		$(0.15	)
Net realized and unrealized gain (loss)		3.31			1.24			11.61			8.13			4.76			1.15
Total from investment operations		$3.15			$0.97			$11.35			$7.94			$4.64			$1.00

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$46.90			$44.73			$45.65			$35.67			$28.27			$24.62
Total return (%) (r)(s)(t)(x)		7.12	(n)		2.97			32.79			28.58	(c)		19.20			4.18

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.19	(a)		1.19			1.24			1.24	(c)		1.27			1.30
Expenses after expense reductions (f)		1.18	(a)		1.18			1.22			1.23	(c)		1.26			1.29
Net investment income (loss)		(0.71	)(a)		(0.64	)		(0.66	)		(0.63	)(c)		(0.48	)		(0.60	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$507,563			$471,468			$484,477			$359,698			$320,898			$199,313

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.13	(a)		1.15			1.16			1.19	(c)		1.24			1.27

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$38.16			$39.55			$31.31			$25.06			$22.09			$22.20

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.29	)		$(0.50	)		$(0.49	)		$(0.38	)(c)		$(0.28	)		$(0.30	)
Net realized and unrealized gain (loss)		2.81			1.00			10.10			7.17			4.24			1.04
Total from investment operations		$2.52			$0.50			$9.61			$6.79			$3.96			$0.74

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$39.70			$38.16			$39.55			$31.31			$25.06			$22.09
Total return (%) (r)(s)(t)(x)		6.68	(n)		2.21			31.77			27.64	(c)		18.29			3.41

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.94	(a)		1.94			1.99			1.99	(c)		2.02			2.05
Expenses after expense reductions (f)		1.93	(a)		1.93			1.98			1.98	(c)		2.01			2.04
Net investment income (loss)		(1.46	)(a)		(1.39	)		(1.41	)		(1.38	)(c)		(1.22	)		(1.35	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$38,774			$41,017			$45,337			$34,396			$25,990			$18,791

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.89	(a)		1.90			1.92			1.94	(c)		1.99			2.02

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$38.07			$39.47			$31.24			$25.01			$22.05			$22.16

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.29	)		$(0.50	)		$(0.49	)		$(0.38	)(c)		$(0.28	)		$(0.30	)
Net realized and unrealized gain (loss)		2.82			0.99			10.09			7.15			4.23			1.04
Total from investment operations		$2.53			$0.49			$9.60			$6.77			$3.95			$0.74

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$39.62			$38.07			$39.47			$31.24			$25.01			$22.05
Total return (%) (r)(s)(t)(x)		6.73	(n)		2.19			31.81			27.62	(c)		18.28			3.42

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.94	(a)		1.94			1.98			1.99	(c)		2.02			2.05
Expenses after expense reductions (f)		1.93	(a)		1.93			1.97			1.98	(c)		2.01			2.04
Net investment income (loss)		(1.46	)(a)		(1.40	)		(1.41	)		(1.38	)(c)		(1.23	)		(1.35	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$132,558			$128,817			$128,707			$101,656			$73,071			$43,037

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.89	(a)		1.91			1.92			1.94	(c)		2.00			2.02

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$48.02			$48.74			$37.90			$29.93			$25.96			$25.69

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.12	)		$(0.18	)		$(0.18	)		$(0.13	)(c)		$(0.07	)		$(0.09	)
Net realized and unrealized gain (loss)		3.56			1.35			12.39			8.64			5.03			1.21
Total from investment operations		$3.44			$1.17			$12.21			$8.51			$4.96			$1.12

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$50.48			$48.02			$48.74			$37.90			$29.93			$25.96
Total return (%) (r)(s)(t)(x)		7.23	(n)		3.20			33.14			28.91	(c)		19.45			4.45

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.94	(a)		0.94			0.99			0.99	(c)		1.02			1.05
Expenses after expense reductions (f)		0.93	(a)		0.93			0.98			0.98	(c)		1.01			1.04
Net investment income (loss)		(0.46	)(a)		(0.40	)		(0.41	)		(0.39	)(c)		(0.24	)		(0.35	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$327,106			$315,655			$303,359			$174,275			$96,700			$56,619

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.89	(a)		0.91			0.92			0.95	(c)		1.00			1.02

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$37.99			$39.39			$31.18			$24.96			$22.01			$22.12

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.29	)		$(0.50	)		$(0.49	)		$(0.38	)(c)		$(0.28	)		$(0.30	)
Net realized and unrealized gain (loss)		2.81			0.99			10.07			7.14			4.22			1.04
Total from investment operations		$2.52			$0.49			$9.58			$6.76			$3.94			$0.74

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$39.53			$37.99			$39.39			$31.18			$24.96			$22.01
Total return (%) (r)(s)(t)(x)		6.71	(n)		2.19			31.80			27.63	(c)		18.27			3.43

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.94	(a)		1.94			1.99			1.99	(c)		2.02			2.05
Expenses after expense reductions (f)		1.93	(a)		1.93			1.98			1.98	(c)		2.01			2.04
Net investment income (loss)		(1.46	)(a)		(1.40	)		(1.41	)		(1.38	)(c)		(1.22	)		(1.36	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$5,852			$5,715			$5,534			$4,256			$3,073			$2,516

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.89	(a)		1.91			1.92			1.95	(c)		1.99			2.02

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$42.45			$43.55			$34.17			$27.17			$23.76			$23.70

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.21	)		$(0.36	)		$(0.35	)		$(0.26	)(c)		$(0.18	)		$(0.20	)
Net realized and unrealized gain (loss)		3.14			1.15			11.10			7.80			4.58			1.11
Total from investment operations		$2.93			$0.79			$10.75		��	$7.54			$4.40			$0.91

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$44.40			$42.45			$43.55			$34.17			$27.17			$23.76
Total return (%) (r)(s)(t)(x)		6.98	(n)		2.69			32.46			28.27	(c)		18.88			3.93

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.44	(a)		1.44			1.48			1.49	(c)		1.52			1.55
Expenses after expense reductions (f)		1.43	(a)		1.43			1.48			1.49	(c)		1.51			1.54
Net investment income (loss)		(0.96	)(a)		(0.90	)		(0.91	)		(0.89	)(c)		(0.72	)		(0.84	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$29,077			$29,339			$28,071			$23,625			$17,031			$14,946

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.39	(a)		1.41			1.42			1.45	(c)		1.49			1.52

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$44.71			$45.63			$35.66			$28.26			$24.61			$24.46

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.17	)		$(0.27	)		$(0.27	)		$(0.20	)(c)		$(0.13	)		$(0.15	)
Net realized and unrealized gain (loss)		3.31			1.24			11.61			8.14			4.77			1.15
Total from investment operations		$3.14			$0.97			$11.34			$7.94			$4.64			$1.00

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$46.87			$44.71			$45.63			$35.66			$28.26			$24.61
Total return (%) (r)(s)(t)(x)		7.10	(n)		2.97			32.77			28.59	(c)		19.21			4.18

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.19	(a)		1.19			1.24			1.24	(c)		1.27			1.30
Expenses after expense reductions (f)		1.18	(a)		1.18			1.23			1.23	(c)		1.26			1.29
Net investment income (loss)		(0.71	)(a)		(0.65	)		(0.66	)		(0.65	)(c)		(0.49	)		(0.60	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$75,037			$80,242			$79,534			$53,199			$20,180			$9,732

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		1.14	(a)		1.16			1.17			1.20	(c)		1.25			1.27

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$46.72			$47.47			$36.95			$29.19			$25.34			$25.10

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.11	)		$(0.17	)		$(0.17	)		$(0.13	)(c)		$(0.06	)		$(0.09	)
Net realized and unrealized gain (loss)		3.46			1.31			12.06			8.43			4.90			1.18
Total from investment operations		$3.35			$1.14			$11.89			$8.30			$4.84			$1.09

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$49.09			$46.72			$47.47			$36.95			$29.19			$25.34
Total return (%) (r)(s)(t)(x)		7.24	(n)		3.22			33.12			28.92	(c)		19.45			4.44

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.94	(a)		0.94			0.99			0.99	(c)		1.02			1.05
Expenses after expense reductions (f)		0.93	(a)		0.93			0.98			0.99	(c)		1.01			1.04
Net investment income (loss)		(0.46	)(a)		(0.40	)		(0.41	)		(0.39	)(c)		(0.24	)		(0.37	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$25,967			$25,310			$23,004			$14,443			$8,141			$2,234

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.89	(a)		0.91			0.92			0.95	(c)		1.00			1.02

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$48.38			$49.03			$38.09			$30.05			$26.03			$25.73

Income (loss) from investment operations
Net investment income (loss) (d)		$(0.09	)		$(0.13	)		$(0.13	)		$(0.10	)(c)		$(0.04	)		$(0.07	)
Net realized and unrealized gain (loss)		3.58			1.37			12.44			8.68			5.05			1.22
Total from investment operations		$3.49			$1.24			$12.31			$8.58			$5.01			$1.15

Less distributions declared to shareholders
From net realized gain		$(0.98	)		$(1.89	)		$(1.37	)		$(0.54	)		$(0.99	)		$(0.85	)
Net asset value, end of period (x)		$50.89			$48.38			$49.03			$38.09			$30.05			$26.03
Total return (%) (r)(s)(t)(x)		7.28	(n)		3.33			33.24			29.03	(c)		19.59			4.57

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.85	(a)		0.84			0.89			0.90	(c)		0.92			0.95
Expenses after expense reductions (f)		0.84	(a)		0.83			0.88			0.89	(c)		0.91			0.94
Net investment income (loss)		(0.36	)(a)		(0.30	)		(0.31	)		(0.30	)(c)		(0.13	)		(0.27	)
Portfolio turnover		17	(n)		32			30			43			30			43
Net assets at end of period (000 omitted)		$198,377			$168,352			$138,924			$95,534			$33,411			$7,079

Supplemental Ratios (%):
Ratios of expenses to average net assets after expense reductions excluding short sale expenses and interest expense and fees (f)		0.79	(a)		0.81			0.82			0.85	(c)		0.90			0.92

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Technology Fund (the fund) is anon-diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

General– The preparation of financial statements in conformity with U.S. generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. In the preparation of these financial statements, management has evaluated subsequent events occurring after the date of the fund’s Statement of Assets and Liabilities through the date that the financial statements were issued. The fund invests primarily in securities of issuers in the technology industry. Issuers in a single industry can react similarly to market, currency, political, economic, regulatory, geopolitical, and other conditions. The value of stocks in the technology sector can be very volatile due to the rapid pace of product change, technological developments, and other factors.

In March 2020, the FASB issued Accounting Standards Update 2020-04, Reference Rate Reform (Topic 848) – Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the London Interbank Offered Rate (LIBOR) and other IBOR-based reference rates as of the end of 2021. The temporary relief provided by ASU 2020-04 is effective for certain reference rate-related contract modifications that occur during the period from March 12, 2020 through December 31, 2022. Management is evaluating the impact of ASU 2020-04 on the fund’s investments, derivatives, debt and other contracts that will undergo reference rate-related modifications as a result of the reference rate reform.

Notes to Financial Statements (unaudited) – continued

Investment Valuations– Equity securities, including restricted equity securities and equity securities sold short, are generally valued at the last sale or official closing price on their primary market or exchange as provided by a third-party pricing service. Equity securities, for which there were no sales reported that day, are generally valued at the last quoted daily bid quotation on their primary market or exchange as provided by a third-party pricing service. Equity securities sold short, for which there were no sales reported for that day, are generally valued at the last quoted daily ask quotation on their primary market or exchange as provided by a third-party pricing service.Short-term instruments with a maturity at issuance of 60 days or less may be valued at amortized cost, which approximates market value. Exchange-traded options are generally valued at the last sale or official closing price on their primary exchange as provided by a third-party pricing service. Exchange-traded options for which there were no sales reported that day are generally valued at the last daily bid quotation on their primary exchange as provided by a third-party pricing service. For put options, the position may be valued at the last daily ask quotation if there are no trades reported during the day. Options not traded on an exchange are generally valued at a broker/dealer bid quotation. Foreign currency options are generally valued at valuations provided by a third-party pricing service.Open-end investment companies are generally valued at net asset value per share. Securities and other assets generally valued on the basis of information from a third-party pricing service may also be valued at a broker/dealer bid quotation. In determining values, third-party pricing services can utilize both transaction data and market information such as yield, quality, coupon rate, maturity, type of issue, trading characteristics, and other market data. The values of foreign securities and other assets and liabilities expressed in foreign currencies are converted to U.S. dollars using the mean of bid and asked prices for rates provided by a third-party pricing service.

Notes to Financial Statements (unaudited) – continued

material effect on the value of securities traded in foreign markets. Accordingly, the fund’s foreign equity securities may often be valued at fair value. The adviser generally relies on third-party pricing services or other information (such as the correlation with price movements of similar securities in the same or other markets; the type, cost and investment characteristics of the security; the business and financial condition of the issuer; and trading and other market data) to assist in determining whether to fair value and at what value to fair value an investment. The value of an investment for purposes of calculating the fund’s net asset value can differ depending on the source and method used to determine value. When fair valuation is used, the value of an investment used to determine the fund’s net asset value may differ from quoted or published prices for the same investment. There can be no assurance that the fund could obtain the fair value assigned to an investment if it were to sell the investment at the same time at which the fund determines its net asset value per share.



Financial Instruments	Level 1			Level 2		Level 3		Total
Equity Securities:
United States		$1,201,672,754			$—		$—		$1,201,672,754
United Kingdom		35,458,000			—		—		35,458,000
Canada		20,515,771			—		—		20,515,771
China		12,111,361			7,319,890		—		19,431,251
Netherlands		6,729,538			8,074,921		—		14,804,459
Israel		9,596,816			—		—		9,596,816
Japan		1,309,401			7,185,679		—		8,495,080
Mutual Funds		21,849,909			—		—		21,849,909
Total		$1,309,243,550			$22,580,490		$—		$1,331,824,040
Securities Sold Short		$(28,723	)		$—		$—		$(28,723	)

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

to foreign exchange rate movements on receivables, payables, income and expenses are recorded for financial statement purposes as foreign currency transaction gains and losses. That portion of both realized and unrealized gains and losses on investments that results from fluctuations in foreign currency exchange rates is not separately disclosed.

Derivatives– The fund uses derivatives primarily to increase or decrease exposure to a particular market or segment of the market, or security, to increase or decrease interest rate or currency exposure, or as alternatives to direct investments. Derivatives are used for hedging ornon-hedging purposes. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains. When the fund uses derivatives as an investment to increase market exposure, or for hedging purposes, gains and losses from derivative instruments may be substantially greater than the derivative’s original cost.

The derivative instruments used by the fund during the period were written options. Depending on the type of derivative, the fund may exit a derivative position by entering into an offsetting transaction with a counterparty or exchange, negotiating an agreement with the derivative counterparty, or novating the position to a third party. At February 29, 2020, the fund did not have any outstanding derivative instruments.

The following table presents, by major type of derivative contract, the realized gain (loss) on derivatives held by the fund for the six months ended February 29, 2020 as reported in the Statement of Operations:



Risk	Written Options
Equity		$606,271

There is no change in unrealized appreciation (depreciation) on derivative transactions at period end.

Derivative counterparty credit risk is managed through formal evaluation of the creditworthiness of all potential counterparties. On certain, but not all, uncleared derivatives, the fund attempts to reduce its exposure to counterparty credit risk whenever possible by entering into an ISDA Master Agreement on a bilateral basis. The ISDA Master Agreement gives each party to the agreement the right to terminate all transactions traded under such agreement if there is a specified deterioration in the credit quality of the other party. Upon an event of default or a termination of the ISDA Master Agreement, thenon-defaulting party has the right to close out all transactions traded under such agreement and to net amounts owed under each agreement to one net amount payable by one party to the other. This right to close out and net payments across all transactions traded under the ISDA Master Agreement could result in a reduction of the fund’s credit risk to such counterparty equal to any amounts payable by the fund under the applicable transactions, if any.

Collateral and margin requirements differ by type of derivative. For cleared derivatives (e.g., futures contracts, cleared swaps, and exchange-traded options), margin requirements are set by the clearing broker and the clearing house and collateral, in the form of cash or securities, is posted by the fund directly with the clearing broker. Collateral terms are counterparty agreement specific for uncleared derivatives (e.g., forward foreign currency exchange contracts, uncleared swap agreements, and uncleared options) and collateral, in the form of cash and securities, is held in

Notes to Financial Statements (unaudited) – continued

segregated accounts with the fund’s custodian in connection with these agreements. For derivatives traded under an ISDA Master Agreement, which contains a collateral support annex, the collateral requirements are netted across all transactions traded under such counterparty-specific agreement and an amount is posted from one party to the other to collateralize such obligations. Cash that has been segregated or delivered to cover the fund’s collateral or margin obligations under derivative contracts, if any, will be reported separately in the Statement of Assets and Liabilities as restricted cash for uncleared derivatives and/or deposits with brokers for cleared derivatives. Securities pledged as collateral or margin for the same purpose, if any, are noted in the Portfolio of Investments. The fund may be required to make payments of interest on uncovered collateral or margin obligations with the broker. Any such payments are included in “Interest expense and fees” in the Statement of Operations.

Written Options– In exchange for a premium, the fund wrote call options on securities for which it anticipated the price would decline and also wrote put options on securities for which it anticipated the price would increase. At the time the option was written, the fund believed the premium received exceeded the potential loss that could result from adverse price changes in the options’ underlying securities. In a written option, the fund as the option writer grants the buyer the right to purchase from, or sell to, the fund a specified number of shares or units of a particular security, currency or index at a specified price within a specified period of time.

The premium received is initially recorded as a liability in the Statement of Assets and Liabilities. The option is subsequentlymarked-to-market daily with the difference between the premium received and the market value of the written option being recorded as unrealized appreciation or depreciation. When a written option expires, the fund realizes a gain equal to the amount of the premium received. The difference between the premium received and the amount paid on effecting a closing transaction is considered a realized gain or loss. When a written call option is exercised, the premium received is offset against the proceeds to determine the realized gain or loss. When a written put option is exercised, the premium reduces the cost basis of the security purchased by the fund.

At the initiation of the written option contract, for exchange traded options, the fund is required to deposit securities or cash as collateral with the custodian for the benefit of the broker or directly with the clearing broker, based on the type of option. For uncleared options, the fund may post collateral subject to the terms of an ISDA Master Agreement as generally described above if the market value of the options contract moves against it. The fund, as writer of an option, may have no control over whether the underlying securities may be sold (call) or purchased (put) and, as a result, bears the market risk of an unfavorable change in the price of the securities underlying the written option. Losses from writing options can exceed the premium received and can exceed the potential loss from an ordinary buy and sell transaction. Although the fund’s market risk may be significant, the maximum counterparty credit risk to the fund is equal to the market value of any collateral posted to the broker. For uncleared options, this risk is mitigated in cases where there is an ISDA Master Agreement between the fund and the counterparty providing for netting as described above.

Short Sales– The fund entered into short sales whereby it sells a security it does not own in anticipation of a decline in the value of that security. The fund will realize a gain

Notes to Financial Statements (unaudited) – continued

if the security price decreases and a loss if the security price increases between the date of the short sale and the date on which the fund replaces the borrowed security. Losses from short sales can exceed the proceeds of the security sold; and they can also exceed the potential loss from an ordinary buy and sell transaction. The amount of any premium, dividends, or interest the fund may be required to pay in connection with a short sale will be recognized as a fund expense. During the six months ended February 29, 2020, this expense amounted to $312,631. The fund segregates cash or marketable securities in an amount that, when combined with the amount of proceeds from the short sale deposited with the broker, at least equals the current market value of the security sold short.

Security Loans– Under its Securities Lending Agency Agreement with the fund, State Street Bank and Trust Company, as lending agent, loans the securities of the fund to certain qualified institutions (the “Borrowers”) approved by the fund. Security loans can be terminated at the discretion of either the lending agent or the fund and the related securities must be returned within the earlier of the standard trade settlement period for such securities or within three business days. The loans are collateralized by cash and/or U.S. Treasury and federal agency obligations in an amount typically at least equal to the market value of the securities loaned. On loans collateralized by cash, the cash collateral is invested in a money market fund. The market value of the loaned securities is determined at the close of business of the fund and any additional required collateral is delivered to the fund on the next business day. The lending agent provides the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income. At February 29, 2020, there were no securities on loan or collateral outstanding.

Investment Transactions and Income– Investment transactions are recorded on the trade date. Dividends received in cash are recorded on theex-dividend date. Certain

Notes to Financial Statements (unaudited) – continued

dividends from foreign securities will be recorded when the fund is informed of the dividend if such information is obtained subsequent to theex-dividend date. Dividend payments received in additional securities are recorded on theex-dividend date in an amount equal to the value of the security on such date.

Book/tax differences primarily relate to net operating losses, wash sale loss deferrals, straddle loss deferrals, and treating a portion of the proceeds from redemptions as a distribution for tax purposes.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$8,438,597
Long-term capital gains		43,001,600

Total distributions		$51,440,197

Notes to Financial Statements (unaudited) – continued

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$692,096,791
Gross appreciation	648,539,711

Gross depreciation	(8,841,185	)
Net unrealized appreciation (depreciation)	$639,698,526

As of 8/31/19

Undistributed long-term capital gain	27,685,821
Post-October capital loss deferral	(2,429,753	)
Late year ordinary loss deferral	(5,219,836	)
Other temporary differences	(415	)
Net unrealized appreciation (depreciation)	551,097,210

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.



	Six months ended 2/29/20		Year ended 8/31/19
Class A		$10,280,837		$20,061,820
Class B		1,005,040		2,165,547
Class C		3,234,463		6,237,227
Class I		6,452,463		11,628,427
Class R1		145,838		267,264
Class R2		661,860		1,292,150
Class R3		1,720,727		3,217,992
Class R4		561,942		875,507
Class R6		3,622,879		5,694,263
Total		$27,686,049		$51,440,197

Notes to Financial Statements (unaudited) – continued

(3) Transactions with Affiliates


Up to $1 billion	0.75	%
In excess of $1 billion and up to $2.5 billion	0.70	%
In excess of $2.5 billion	0.65	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $67,606, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.73% of the fund’s average daily net assets.

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $95,838 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A shares of the fund.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.25%		$617,159
Class B		0.75%		0.25%		1.00%		1.00%		205,320
Class C		0.75%		0.25%		1.00%		1.00%		662,147
Class R1		0.75%		0.25%		1.00%		1.00%		29,759
Class R2		0.25%		0.25%		0.50%		0.50%		75,502
Class R3		—		0.25%		0.25%		0.25%		102,230
Total Distribution and Service Fees										$1,692,117

(d)

(e)

Notes to Financial Statements (unaudited) – continued



	Amount
Class A		$2,745
Class B		41,779
Class C		7,328

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $69,880, which equated to 0.0105% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $598,747.

Other–The fund invests in the MFS Institutional Money Market Portfolio which is managed by MFS and seeks current income consistent with preservation of capital and liquidity. This money market fund does not pay a management fee to MFS but does incur investment and operating costs.

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $36,614, which is included in “Other” income in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short sales and short-term obligations, aggregated $228,192,850 and $273,660,556, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares sold
Class A		1,069,435			$50,462,650			1,975,893			$83,003,835
Class B		4,434			175,717			120,191			4,301,477
Class C		269,108			10,741,401			677,632			24,341,867
Class I		933,833			47,703,970			2,550,161			113,611,517
Class R1		18,125			727,885			47,490			1,684,411
Class R2		112,471			5,023,965			299,032			11,915,742
Class R3		265,676			12,633,539			666,590			27,985,848
Class R4		141,415			6,866,378			204,948			8,719,675
Class R6		912,666			46,640,355			1,474,545			66,395,491
		3,727,163			$180,975,860			8,016,482			$341,959,863

Shares issued to shareholders in reinvestment of distributions
Class A		219,633			$9,997,680			520,757			$19,351,348
Class B		25,706			992,506			67,268			2,143,844
Class C		77,734			2,994,325			179,366			5,703,832
Class I		115,169			5,640,993			255,108			10,158,414
Class R1		3,780			145,294			8,390			266,220
Class R2		14,422			621,865			32,936			1,163,614
Class R3		37,818			1,720,727			86,645			3,217,992
Class R4		10,015			476,930			18,432			714,074
Class R6		60,950			3,008,484			113,449			4,548,175
		565,227			$25,598,804			1,282,351			$47,267,513

Shares reacquired
Class A		(1,006,198	)		$(47,145,423	)		(2,568,696	)		$(105,539,945	)
Class B		(128,483	)		(5,185,735	)		(258,701	)		(9,209,777	)
Class C		(383,957	)		(15,151,627	)		(734,328	)		(26,311,197	)
Class I		(1,142,466	)		(58,234,918	)		(2,456,918	)		(109,249,971	)
Class R1		(24,265	)		(950,492	)		(45,940	)		(1,644,386	)
Class R2		(163,088	)		(7,257,318	)		(285,477	)		(11,417,715	)
Class R3		(497,307	)		(23,358,546	)		(701,327	)		(29,333,688	)
Class R4		(164,160	)		(8,163,606	)		(166,210	)		(7,057,361	)
Class R6		(555,271	)		(28,373,618	)		(941,393	)		(42,393,928	)
		(4,065,195	)		$(193,821,283	)		(8,158,990	)		$(342,157,968	)

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Net change
Class A		282,870			$13,314,907			(72,046	)		$(3,184,762	)
Class B		(98,343	)		(4,017,512	)		(71,242	)		(2,764,456	)
Class C		(37,115	)		(1,415,901	)		122,670			3,734,502
Class I		(93,464	)		(4,889,955	)		348,351			14,519,960
Class R1		(2,360	)		(77,313	)		9,940			306,245
Class R2		(36,195	)		(1,611,488	)		46,491			1,661,641
Class R3		(193,813	)		(9,004,280	)		51,908			1,870,152
Class R4		(12,730	)		(820,298	)		57,170			2,376,388
Class R6		418,345			21,275,221			646,601			28,549,738
		227,195			$12,753,381			1,139,843			$47,069,408

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $3,442 and $0, respectively, and are included in “Interest expense and fees” in the Statement of Operations.

Notes to Financial Statements (unaudited) – continued

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)		Change in Unrealized Appreciation or Depreciation			Ending Value
MFS Institutional Money Market Portfolio		$34,879,336		$139,990,751		$153,020,584		$4,624		$(4,218	)		$21,849,909

Affiliated Issuers									Dividend Income			Capital Gain Distributions
MFS Institutional Money Market Portfolio										$219,588			$—

(8) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

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1-800-637-8255

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ACCOUNT SERVICE AND LITERATURE

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1-800-225-2606

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MAILING ADDRESS

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Semiannual Report

February 29, 2020

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MFS® U.S. Government Cash Reserve Fund

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LMM-SEM

MFS® U.S. Government Cash Reserve Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			5
Statement of assets and liabilities			6
Statement of operations			8
Statements of changes in net assets			9
Financial highlights			10
Notes to financial statements			17
Proxy voting policies and information			26
Portfolio holdings information			26
Further information			26
Information about fund contracts and legal claims			26
Provision of financial reports and summary prospectuses			26


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

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LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure (u)

LOGO


Composition including fixed income credit quality (a)(u)
A-1+			10.1%
A-1			85.7%
Other Assets Less Liabilities			4.2%


Maturity breakdown (u)
0 - 7 days			19.8%
8 - 29 days			30.2%
30 - 59 days			29.9%
60 - 89 days			11.1%
90 - 365 days			4.8%
Other Assets Less Liabilities			4.2%

(a)

Ratings are assigned to portfolio securities utilizing ratings from Moody’s, Fitch, and Standard & Poor’s rating agencies and applying the following hierarchy: If all three agencies provide a rating, the middle rating (after dropping the highest and lowest ratings) is assigned; if two of the three agencies rate a security, the lower of the two is assigned. Ratings are shown in the S&P scale. All ratings are subject to change. The fund did not hold unrated securities. The fund is not rated by these agencies.

(u)	For purposes of this presentation, accrued interest, where applicable, is included.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		0.71%		$1,000.00		$1,005.09		$3.54
A	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
B	Actual		0.71%		$1,000.00		$1,005.10		$3.54
B	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
C	Actual		0.71%		$1,000.00		$1,005.10		$3.54
C	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
I	Actual		0.72%		$1,000.00		$1,005.11		$3.59
I	Hypothetical (h)		0.72%		$1,000.00		$1,021.28		$3.62
R1	Actual		0.71%		$1,000.00		$1,005.09		$3.54
R1	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
R2	Actual		0.71%		$1,000.00		$1,005.10		$3.54
R2	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
R3	Actual		0.71%		$1,000.00		$1,005.10		$3.54
R3	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
R4	Actual		0.71%		$1,000.00		$1,005.10		$3.54
R4	Hypothetical (h)		0.71%		$1,000.00		$1,021.33		$3.57
R6	Actual		0.65%		$1,000.00		$1,005.45		$3.24
R6	Hypothetical (h)		0.65%		$1,000.00		$1,021.63		$3.27
529A	Actual		0.76%		$1,000.00		$1,004.84		$3.79
529A	Hypothetical (h)		0.76%		$1,000.00		$1,021.08		$3.82
529B	Actual		0.76%		$1,000.00		$1,004.84		$3.79
529B	Hypothetical (h)		0.76%		$1,000.00		$1,021.08		$3.82
529C	Actual		0.76%		$1,000.00		$1,004.85		$3.79
529C	Hypothetical (h)		0.76%		$1,000.00		$1,021.08		$3.82

(h)	5% class return per year before expenses.

(p)

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
U.S. Government Agencies and Equivalents (y) - 89.3%
Fannie Mae, 1.424%, due 3/02/2020	$	15,970,000	$	15,969,379
Fannie Mae, 1.566%, due 3/04/2020		4,148,000		4,147,468
Fannie Mae, 1.554%, due 3/13/2020		7,180,000		7,176,350
Fannie Mae, 1.590%, due 4/16/2020		13,070,000		13,043,948
Federal Farm Credit Bank, 1.548%, due 3/05/2020		8,700,000		8,698,531
Federal Farm Credit Bank, 1.568%, due 3/17/2020		26,080,000		26,062,150
Federal Farm Credit Bank, 1.588%, due 3/19/2020		5,325,000		5,320,846
Federal Home Loan Bank, 1.584%, due 4/03/2020		24,245,000		24,210,441
Federal Home Loan Bank, 1.576%, due 4/08/2020		8,020,000		8,006,921
Federal Home Loan Bank, 1.6%, due 4/15/2020		8,040,000		8,024,221
Federal Home Loan Bank, 1.603%, due 5/06/2020		10,030,000		10,001,130
Freddie Mac, 1.566%, due 3/09/2020		14,600,000		14,595,003
Freddie Mac, 1.561%, due 4/08/2020		7,518,000		7,505,858
Freddie Mac, 1.571%, due 4/30/2020		8,025,000		8,004,402
Freddie Mac, 1.579%, due 6/17/2020		10,370,000		10,321,935
U.S. Treasury Bill, 1.499%, due 3/12/2020		12,140,000		12,134,547
U.S. Treasury Bill, 1.591%, due 4/14/2020		3,875,000		3,867,607
U.S. Treasury Bill, 1.557%, due 5/14/2020		6,000,000		5,981,192
Total U.S. Government Agencies and Equivalents, at Amortized Cost and Value			$	193,071,929

Repurchase Agreements - 6.5%
JPMorgan Chase & Co. Repurchase Agreement, 1.58%, dated 2/28/2020, due 3/02/2020, total to be received $14,119,859 (secured by U.S. Treasury obligations valued $14,402,257 in a jointly traded account), at Cost and Value	$	14,118,000	$	14,118,000

Other Assets, Less Liabilities - 4.2%			8,988,662
Net Assets - 100.0%			$	216,178,591

(y)	The rate shown represents an annualized yield at time of purchase.

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at cost and value	$207,189,929
Cash	245
Receivables for
Fund shares sold	9,474,404
Interest	1,239
Other assets	920
Total assets	$216,666,737

Liabilities
Payables for
Distributions	$1,829
Fund shares reacquired	343,020
Payable to affiliates
Investment adviser	6,610
Administrative services fee	312
Shareholder servicing costs	92,949
Program manager fees	111
Payable for independent Trustees’ compensation	5,381
Accrued expenses and other liabilities	37,934
Total liabilities	$488,146
Net assets	$216,178,591

Net assets consist of
Paid-in capital	$216,186,117
Total distributable earnings (loss)	(7,526	)
Net assets	$216,178,591
Shares of beneficial interest outstanding	216,408,598

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share
Class A		$103,115,067		103,225,371		$1.00
Class B		8,255,220		8,264,206		1.00
Class C		17,592,387		17,610,355		1.00
Class I		1,133,375		1,134,337		1.00
Class R1		7,870,638		7,879,392		1.00
Class R2		32,233,524		32,265,109		1.00
Class R3		15,486,410		15,503,556		1.00
Class R4		2,706,910		2,710,011		1.00
Class R6		119,249		119,386		1.00
Class 529A		20,790,102		20,813,481		1.00
Class 529B		215,666		215,910		1.00
Class 529C		6,660,043		6,667,484		1.00

A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, Class C, Class 529B, and Class 529C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, R6, and 529A.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Interest	$1,776,564
Expenses
Management fee	$408,241
Distribution and service fees	438,357
Shareholder servicing costs	183,610
Program manager fees	6,686
Administrative services fee	18,568
Independent Trustees’ compensation	5,399
Custodian fee	9,201
Shareholder communications	8,593
Audit and tax fees	19,500
Legal fees	979
Registration fees	63,902
Miscellaneous	20,443
Total expenses	$1,183,479
Reduction of expenses by investment adviser and distributor	(448,702	)
Net expenses	$734,777
Net investment income (loss)	$1,041,787
Change in net assets from operations	$1,041,787

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$1,041,787			$3,428,421
Net realized gain (loss)		—			1
Change in net assets from operations		$1,041,787			$3,428,422
Total distributions to shareholders		$(1,041,787	)		$(3,428,422	)
Change in net assets from fund share transactions		$3,967,947			$(12,531,450	)
Total change in net assets		$3,967,947			$(12,531,450	)

Net assets
At beginning of period		212,210,644			224,742,094
At end of period		$216,178,591			$212,210,644

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS

The financial highlights table is intended to help you understand the fund’s financial performance for the semiannual period and the past 5 fiscal years (or life of a particular share class, if shorter). Certain information reflects financial results for a single fund share. The total returns in the table represent the rate that an investor would have earned (or lost) on an investment in the fund share class (assuming reinvestment of all distributions) held for the entire period.


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.58			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.97	(a)		0.98			0.94			0.91	(c)		0.91		0.92
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.50	(c)		0.23		0.07
Net investment income (loss)		1.03	(a)		1.57			0.76			0.08	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$103,115			$99,511			$100,463			$105,859			$120,740		$122,085

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.58			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.72	(a)		1.73			1.69			1.66	(c)		1.66		1.67
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.51	(c)		0.23		0.07
Net investment income (loss)		1.03	(a)		1.57			0.72			0.07	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$8,255			$8,977			$11,664			$17,338			$18,096		$18,831

	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.58			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.72	(a)		1.73			1.69			1.66	(c)		1.66		1.67
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.50	(c)		0.24		0.07
Net investment income (loss)		1.04	(a)		1.57			0.68			0.07	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$17,592			$19,438			$18,451			$38,458			$48,749		$42,522

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended 8/31/19 (i)
Class I	Six months ended 2/29/20			Year ended 8/31/19 (i)
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02
Net realized and unrealized gain (loss)		—			0.00	(w)
Total from investment operations		$0.01			$0.02

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)
Net asset value, end of period		$1.00			$1.00
Total return (%) (r)(t)		0.51	(n)		1.52	(n)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.73	(a)		0.73	(a)
Expenses after expense reductions (f)		0.72	(a)		0.72	(a)
Net investment income (loss)		0.88	(a)		1.60	(a)
Net assets at end of period (000 omitted)		$1,133			$56


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.57			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.72	(a)		1.73			1.69			1.66	(c)		1.66		1.67
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.50	(c)		0.23		0.07
Net investment income (loss)		1.02	(a)		1.57			0.72			0.07	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$7,871			$7,610			$8,305			$12,236			$14,569		$14,363

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.57			0.76			0.08	(c)��		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.22	(a)		1.23			1.19			1.16	(c)		1.16		1.17
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.51	(c)		0.23		0.07
Net investment income (loss)		1.03	(a)		1.57			0.73			0.08	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$32,234			$31,672			$34,993			$48,184			$51,537		$53,058

	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.57			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.97	(a)		0.98			0.94			0.91	(c)		0.91		0.92
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.51	(c)		0.23		0.07
Net investment income (loss)		1.03	(a)		1.55			0.73			0.08	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$15,486			$16,471			$26,227			$35,196			$37,650		$44,872

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.01			$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.51	(n)		1.57			0.76			0.08	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.72	(a)		0.73			0.69			0.67	(c)		0.66		0.67
Expenses after expense reductions (f)		0.71	(a)		0.72			0.68			0.52	(c)		0.23		0.07
Net investment income (loss)		1.02	(a)		1.57			0.74			0.08	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$2,707			$2,676			$2,729			$3,250			$3,077		$3,034


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19 (i)
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.01			$0.02
Net realized and unrealized gain (loss)		—			0.00	(w)
Total from investment operations		$0.01			$0.02

Less distributions declared to shareholders
From net investment income		$(0.01	)		$(0.02	)
Net asset value, end of period		$1.00			$1.00
Total return (%) (r)(t)		0.55	(n)		1.58	(n)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.66	(a)		0.66	(a)
Expenses after expense reductions (f)		0.65	(a)		0.65	(a)
Net investment income (loss)		1.04	(a)		1.65	(a)
Net assets at end of period (000 omitted)		$119			$54

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15
	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.00	(w)		$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.00	(w)		$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.00	)(w)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.48	(n)		1.53			0.71			0.06	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.02	(a)		1.03			1.00			1.01	(c)		1.00		1.02
Expenses after expense reductions (f)		0.76	(a)		0.77			0.73			0.53	(c)		0.23		0.07
Net investment income (loss)		0.97	(a)		1.52			0.73			0.06	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$20,790			$19,061			$15,197			$13,208			$12,841		$11,383

	Six months ended 2/29/20			Year ended
Class 529B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15

	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.00	(w)		$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.00	(w)		$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.00	)(w)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.48	(n)		1.53			0.71			0.06	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.77	(a)		1.78			1.75			1.76	(c)		1.76		1.77
Expenses after expense reductions (f)		0.76	(a)		0.77			0.73			0.53	(c)		0.22		0.07
Net investment income (loss)		0.98	(a)		1.51			0.71			0.06	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$216			$247			$293			$348			$355		$440

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16		8/31/15

	(unaudited)
Net asset value, beginning of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.00	(w)		$0.02			$0.01			$0.00	(c)(w)		$0.00		$0.00
Net realized and unrealized gain (loss)		—			0.00	(w)		—			(0.00	)(w)		—		0.00	(w)
Total from investment operations		$0.00	(w)		$0.02			$0.01			$0.00	(w)		$0.00		$0.00	(w)

Less distributions declared to shareholders
From net investment income		$(0.00	)(w)		$(0.02	)		$(0.01	)		$(0.00	)(w)		$—		$—
Net asset value, end of period		$1.00			$1.00			$1.00			$1.00			$1.00		$1.00
Total return (%) (r)(t)		0.48	(n)		1.53			0.71			0.06	(c)		0.00		0.00	(w)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.77	(a)		1.78			1.75			1.76	(c)		1.76		1.77
Expenses after expense reductions (f)		0.76	(a)		0.77			0.73			0.54	(c)		0.24		0.07
Net investment income (loss)		0.97	(a)		1.52			0.70			0.06	(c)		0.00		0.00
Net assets at end of period (000 omitted)		$6,660			$6,437			$6,419			$6,957			$6,728		$5,866

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(i)	For Class I and Class R6, the period is from the class inception, September 18, 2018, through the stated period end.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(t)	Total returns do not include any applicable sales charges.

(w)	Per share amount was less than $0.01 and total return or ratio was less than 0.01%, as applicable.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS U.S. Government Cash Reserve Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

Investment Valuations– Pursuant to procedures approved by the Board of Trustees, investments held by the fund are generally valued at amortized cost, which approximates market value. Amortized cost involves valuing an instrument at its cost as

Notes to Financial Statements (unaudited) – continued

adjusted for amortization of premium or accretion of discount rather than its current market value. The amortized cost value of an instrument can be different from the market value of an instrument.



Financial Instruments	Level 1		Level 2		Level 3		Total
Short-Term Securities		$—		$207,189,929		$—		$207,189,929

For further information regarding security characteristics, see the Portfolio of Investments.

Repurchase Agreements– The fund enters into repurchase agreements under the terms of Master Repurchase Agreements with approved counterparties. Each repurchase agreement is recorded at cost. The fund requires that the securities collateral in a repurchase transaction be transferred to a custodian. The fund monitors, on a daily basis, the value of the collateral to ensure that its value, including accrued interest, is greater than amounts owed to the fund under each such repurchase agreement. Upon an event of default under a Master Repurchase Agreement, thenon-defaulting party may close out all transactions traded under such agreement and net amounts owed under each transaction to one net amount payable by one party to the other. Absent an event of default, the Master Repurchase Agreement does not result in an offset of reported amounts of assets and liabilities in the Statement of Assets and Liabilities across transactions between the fund and the applicable counterparty. The fund and other funds managed by MFS may utilize a joint trading account for the purpose of entering into one or more repurchase agreements. At February 29, 2020, the fund had investments in repurchase agreements with a gross value of $14,118,000 included in investments in unaffiliated issuers in the Statement of Assets and Liabilities. The value of the related collateral exceeded the value of the repurchase agreements at period end.

Notes to Financial Statements (unaudited) – continued

Investment Transactions and Income– Investment transactions are recorded on the trade date. Interest income is recorded on the accrual basis. All premium and discount is amortized or accreted for financial statement purposes in accordance with U.S. generally accepted accounting principles.

During the year ended August 31, 2019, there were no significant adjustments due to differences between book and tax accounting.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$3,428,422

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$207,189,929

As of 8/31/19

Capital loss carryforwards	(4	)
Other temporary differences	(7,522	)

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.

As of August 31, 2019, the fund had capital loss carryforwards available to offset future realized gains. These net capital losses may be carried forward indefinitely and their character is retained as short-term and/or long-term losses. Such losses are characterized as follows:


Short-Term			$(4	)

Notes to Financial Statements (unaudited) – continued

Multiple Classes of Shares of Beneficial Interest– The fund offers multiple classes of shares, which differ in their respective distribution, service, and program manager fees. The fund’s income and common expenses are allocated to shareholders based on the value of settled shares outstanding of each class. The fund’s realized and unrealized gain (loss) are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B and Class 529B shares will convert to Class A and Class 529A shares, respectively, approximately eight years after purchase. Class C and Class 529C shares will convert to Class A and Class 529A shares, respectively, approximately ten years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:



	Six months ended 2/29/20		Year ended 8/31/19 (i)
Class A		$495,227		$1,584,216
Class B		43,518		162,414
Class C		90,651		317,540
Class I		1,012		1,185
Class R1		38,230		127,647
Class R2		150,992		527,732
Class R3		78,402		291,144
Class R4		13,791		42,820
Class R6		389		819
Class 529A		96,865		268,010
Class 529B		1,171		3,915
Class 529C		31,539		100,980
Total		$1,041,787		$3,428,422

(i)	For Class I and Class R6, the period is from the class inception, September 18, 2018, through the stated period end.

(3) Transactions with Affiliates

Investment Adviser– The fund has an investment advisory agreement with MFS to provide overall investment management and related administrative services and facilities to the fund. The management fee is computed daily and paid monthly at an annual rate of 0.40% of the fund’s average daily net assets.

MFS has also agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $10,345, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.39% of the fund’s average daily net assets.

Distributor– The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Notes to Financial Statements (unaudited) – continued

The fund’s distribution plan provides that the fund will pay MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, for services provided by MFD and financial intermediaries in connection with the distribution and servicing of certain share classes. One component of the plan is a distribution fee paid to MFD and another component of the plan is a service fee paid to MFD. MFD may subsequently pay all, or a portion, of the distribution and/or service fees to financial intermediaries.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.00%		$120,593
Class B		0.75%		0.25%		1.00%		0.00%		42,251
Class C		0.75%		0.25%		1.00%		0.00%		87,328
Class R1		0.75%		0.25%		1.00%		0.00%		37,363
Class R2		0.25%		0.25%		0.50%		0.00%		73,099
Class R3		—		0.25%		0.25%		0.00%		19,091
Class 529A		—		0.25%		0.25%		0.00%		25,029
Class 529B		0.75%		0.25%		1.00%		0.00%		1,190
Class 529C		0.75%		0.25%		1.00%		0.00%		32,413
Total Distribution and Service Fees										$438,357

(d)

(e)

The annual effective rates represent actual fees incurred under the distribution plan for the six months ended February 29, 2020 based on each class’s average daily net assets. MFD has agreed in writing to waive any distribution and/or service fees for Class A, Class B, Class C, Class R1, Class R2, Class R3, Class 529A, Class 529B, and Class 529C. This written agreement will continue until modified by the fund’s Board of Trustees, but such agreement will continue until at least December 31, 2020. These reductions, for the six months ended February 29, 2020, for Class A, Class B, Class C, Class R1, Class R2, Class R3, Class 529A, Class 529B, and Class 529C amounted to $120,593, $42,251, $87,328, $37,363, $73,099, $19,091, $25,029, $1,190, and $32,413, respectively, and are included in the reduction of total expenses in the Statement of Operations.

Certain Class A shares are subject to a contingent deferred sales charge (CDSC) in the event of a shareholder redemption within 18 months of purchase. Class B and Class 529B shares are subject to a CDSC in the event of a shareholder redemption within six years of purchase. Class C and Class 529C shares are subject to a CDSC in the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the six months ended February 29, 2020, were as follows:



	Amount
Class A		$113
Class B		15,208
Class C		3,229
Class 529B		—
Class 529C		350

Notes to Financial Statements (unaudited) – continued



	Fee
Class 529A		$5,006
Class 529B		59
Class 529C		1,621
Total Program Manager Fees		$6,686

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $63,956, which equated to 0.0627% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $119,654.

Notes to Financial Statements (unaudited) – continued

pension expense of $593 and is included in “Independent Trustees’ compensation” in the Statement of Operations for the six months ended February 29, 2020. The liability for deferred retirement benefits payable to those former independent Trustees under the DB plan amounted to $4,612 at February 29, 2020, and is included in “Payable for independent Trustees’ compensation” in the Statement of Assets and Liabilities.

Other– On September 17, 2018, MFS purchased 50,000 shares of Class I for an aggregate amount of $50,000 and 50,000 shares of Class R6 for an aggregate amount of $50,000 as an initial investment in the class.

At February 29, 2020, MFS held approximately 99% of the outstanding shares of Class R4.

(4) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. The number of shares sold, reinvested and reacquired corresponds to the net proceeds from the sale of shares, reinvestment of distributions and cost of shares reacquired, respectively, since shares are sold and reacquired at $1.00 per share. Transactions in fund shares were as follows:


	Six months ended 2/29/20		Year ended 8/31/19 (i)
Shares sold
Class A		26,796,682		59,431,027
Class B		2,064,923		5,310,326
Class C		8,107,177		24,050,108
Class I		1,334,508		354,368
Class R1		1,468,258		2,191,482
Class R2		7,272,135		10,113,188
Class R3		3,036,393		8,456,459
Class R4		36,929		17,622
Class R6		64,638		72,440
Class 529A		6,950,279		12,190,039
Class 529B		44,533		126,828
Class 529C		2,012,907		3,281,304
		59,189,362		125,595,191

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20			Year ended 8/31/19 (i)
Shares issued to shareholders in reinvestment of distributions
Class A		480,961			1,537,241
Class B		40,891			152,269
Class C		86,622			307,001
Class I		903			888
Class R1		38,217			127,564
Class R2		151,144			527,539
Class R3		78,483			291,144
Class R4		13,791			42,820
Class R6		389			819
Class 529A		96,310			266,573
Class 529B		1,156			3,891
Class 529C		31,356			100,345
		1,020,223			3,358,094

Shares reacquired
Class A		(23,671,484	)		(61,915,466	)
Class B		(2,828,447	)		(8,152,109	)
Class C		(10,041,913	)		(23,369,100	)
Class I		(256,962	)		(299,368	)
Class R1		(1,245,688	)		(3,014,203	)
Class R2		(6,864,830	)		(13,961,909	)
Class R3		(4,099,738	)		(18,513,241	)
Class R4		(19,938	)		(113,448	)
Class R6		(145	)		(18,755	)
Class 529A		(5,314,122	)		(8,587,889	)
Class 529B		(77,101	)		(176,267	)
Class 529C		(1,821,270	)		(3,362,980	)
		(56,241,638	)		(141,484,735	)

Net change
Class A		3,606,159			(947,198	)
Class B		(722,633	)		(2,689,514	)
Class C		(1,848,114	)		988,009
Class I		1,078,449			55,888
Class R1		260,787			(695,157	)
Class R2		558,449			(3,321,182	)
Class R3		(984,862	)		(9,765,638	)
Class R4		30,782			(53,006	)
Class R6		64,882			54,504
Class 529A		1,732,467			3,868,723
Class 529B		(31,412	)		(45,548	)
Class 529C		222,993			18,669
		3,967,947			(12,531,450	)

(i)	For Class I and Class R6, the period is from the class inception, September 18, 2018, through the stated period end.

Notes to Financial Statements (unaudited) – continued

Effective June 1, 2019, purchases of the fund’s Class B and Class 529B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

(5) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $533 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(6) Impacts of COVID-19

(7) Subsequent Event

Effective the close of business May 29, 2020, purchases of the fund are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

PROXY VOTING POLICIES AND INFORMATION

PORTFOLIO HOLDINGS INFORMATION

The fund files monthly portfolio information with the SEC on Form N-MFP. The fund’s Form N-MFP reports are available on the SEC’s website athttp://www.sec.gov. A shareholder can also access the fund’s portfolio holdings as of each month end and the fund’s Form N-MFP reports at mfs.com/openendfunds after choosing “Click here for access to Money Market fund reports”.

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

MFS TALK

1-800-637-8255

24 hours a day

ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

Financial advisors

1-800-343-2829

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1-800-637-1255

MAILING ADDRESS

MFS Service Center, Inc.

P.O. Box 219341

Kansas City, MO 64121-9341

OVERNIGHT MAIL

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Suite 219341

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Kansas City, MO 64105-1407

Semiannual Report

February 29, 2020

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MFS® Value Fund

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EIF-SEM

MFS® Value Fund

CONTENTS


Letter from the Executive Chair			1
Portfolio composition			2
Expense table			3
Portfolio of investments			6
Statement of assets and liabilities			11
Statement of operations			13
Statements of changes in net assets			14
Financial highlights			15
Notes to financial statements			28
Proxy voting policies and information			40
Quarterly portfolio disclosure			40
Further information			40
Information about fund contracts and legal claims			40
Provision of financial reports and summary prospectuses			40


Contact information			back cover

The report is prepared for the general information of shareholders.

It is authorized for distribution to prospective investors only when preceded or accompanied by a current prospectus.

NOT FDIC INSURED• MAY LOSE VALUE• NO BANK GUARANTEE

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LETTER FROM THE EXECUTIVE CHAIR

Dear Shareholders:

During the first quarter of 2020, market volatility reached levels not seen since the global financial crisis. Optimism heading into the year — on receding trade and

Global central banks have taken aggressive, coordinated steps to cushion the economic and market fallout related to the virus, and

Respectfully,

LOGO

Robert J. Manning

Executive Chair

MFS Investment Management

April 16, 2020

The opinions expressed in this letter are subject to change and may not be relied upon for investment advice. No forecasts can be guaranteed.

PORTFOLIO COMPOSITION

Portfolio structure

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Top ten holdings
JPMorgan Chase & Co.			4.6%
Johnson & Johnson			3.5%
Medtronic PLC			2.9%
Comcast Corp., “A”			2.8%
Accenture PLC, “A”			2.6%
Aon PLC			2.6%
Duke Energy Corp.			2.5%
Honeywell International, Inc.			2.5%
Northrop Grumman Corp.			2.4%
Citigroup, Inc.			2.4%


GICS equity sectors (g)
Financials			28.8%
Health Care			17.2%
Industrials			16.9%
Information Technology			9.6%
Consumer Staples			7.8%
Utilities			6.4%
Materials			3.5%
Communication Services			3.4%
Energy			3.2%
Consumer Discretionary			1.2%
Real Estate			0.4%

(g)	The Global Industry Classification Standard (GICS®) was developed by and/or is the exclusive property of MSCI, Inc. and S&P Global Market Intelligence Inc. (“S&P Global Market Intelligence”). GICS is a service mark of MSCI and S&P Global Market Intelligence and has been licensed for use by MFS.

Percentages are based on net assets as of February 29, 2020.

The portfolio is actively managed and current holdings may be different.

EXPENSE TABLE

Fund expenses borne by the shareholders during the period, September 1, 2019 through February 29, 2020

The example is based on an investment of $1,000 invested at the beginning of the period and held for the entire period September 1, 2019 through February 29, 2020.

Actual Expenses

Hypothetical Example for Comparison Purposes

Expense Table – continued


Share Class		Annualized Expense Ratio		Beginning Account Value 9/01/19		Ending Account Value 2/29/20		Expenses Paid During Period (p) 9/01/19-2/29/20
A	Actual		0.81%		$1,000.00		$979.70		$3.99
A	Hypothetical (h)		0.81%		$1,000.00		$1,020.84		$4.07
B	Actual		1.56%		$1,000.00		$975.83		$7.66
B	Hypothetical (h)		1.56%		$1,000.00		$1,017.11		$7.82
C	Actual		1.56%		$1,000.00		$975.80		$7.66
C	Hypothetical (h)		1.56%		$1,000.00		$1,017.11		$7.82
I	Actual		0.56%		$1,000.00		$981.00		$2.76
I	Hypothetical (h)		0.56%		$1,000.00		$1,022.08		$2.82
R1	Actual		1.56%		$1,000.00		$976.09		$7.66
R1	Hypothetical (h)		1.56%		$1,000.00		$1,017.11		$7.82
R2	Actual		1.06%		$1,000.00		$978.47		$5.21
R2	Hypothetical (h)		1.06%		$1,000.00		$1,019.59		$5.32
R3	Actual		0.81%		$1,000.00		$979.62		$3.99
R3	Hypothetical (h)		0.81%		$1,000.00		$1,020.84		$4.07
R4	Actual		0.56%		$1,000.00		$980.88		$2.76
R4	Hypothetical (h)		0.56%		$1,000.00		$1,022.08		$2.82
R6	Actual		0.45%		$1,000.00		$981.42		$2.22
R6	Hypothetical (h)		0.45%		$1,000.00		$1,022.63		$2.26
529A	Actual		0.83%		$1,000.00		$979.43		$4.08
529A	Hypothetical (h)		0.83%		$1,000.00		$1,020.74		$4.17
529B	Actual		0.98%		$1,000.00		$978.71		$4.82
529B	Hypothetical (h)		0.98%		$1,000.00		$1,019.99		$4.92
529C	Actual		1.61%		$1,000.00		$975.72		$7.91
529C	Hypothetical (h)		1.61%		$1,000.00		$1,016.86		$8.07

(h)	5% class return per year before expenses.

(p)

Notes to Expense Table

For the period from October 1, 2019 through February 29, 2020, the distribution fee for Class 529B was not imposed. Had the distribution fee been imposed throughout the entire six month period, the annualized expense ratio, the actual expenses paid during the period, and the hypothetical expenses paid during the period would have been approximately 1.60%, $7.87, and $8.02 for Class 529B. See Note 3 in the Notes to Financial Statements for additional information.

Expense Table – continued

Each class with a Rule12b-1 service fee is subject to a rebate of a portion of such fee. Such rebates are included in the expense ratios above. For Class 529A shares, this rebate reduced the expense ratio above by 0.03%. See Note 3 in the Notes to Financial Statements for additional information.

PORTFOLIO OF INVESTMENTS

2/29/20 (unaudited)

The Portfolio of Investments is a complete list of all securities owned by your fund. It is categorized by broad-based asset classes.



Issuer	Shares/Par		Value ($)
Common Stocks - 98.4%
Aerospace - 7.5%
Honeywell International, Inc.		7,136,754	$	1,157,367,396
Lockheed Martin Corp.		1,439,434		532,403,454
Northrop Grumman Corp.		3,394,161		1,116,135,903
United Technologies Corp.		4,914,407		641,772,410

			$	3,447,679,163
Alcoholic Beverages - 1.5%
Diageo PLC		19,013,779	$	673,376,101

Apparel Manufacturers - 0.1%
Hanesbrands, Inc.		2,535,133	$	33,565,161

Automotive - 1.0%
Aptiv PLC		4,843,840	$	378,352,343
Lear Corp.		669,982		74,501,998

			$	452,854,341
Broadcasting - 0.1%
Omnicom Group, Inc.		737,122	$	51,067,812

Brokerage & Asset Managers - 2.8%
BlackRock, Inc.		1,004,232	$	464,969,458
NASDAQ, Inc.		5,629,768		577,332,709
T. Rowe Price Group, Inc.		2,087,222		246,313,068

			$	1,288,615,235
Business Services - 7.1%
Accenture PLC, “A”		6,696,704	$	1,209,357,776
Cognizant Technology Solutions Corp., “A”		3,170,671		193,188,984
Equifax, Inc.		3,108,009		441,461,598
Fidelity National Information Services, Inc.		4,909,565		685,964,422
Fiserv, Inc. (a)		6,705,612		733,325,728

			$	3,263,298,508
Cable TV - 2.8%
Comcast Corp., “A”		32,103,316	$	1,297,937,066

Chemicals - 1.7%
PPG Industries, Inc.		7,599,535	$	793,771,431

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Conglomerates - 0.3%
Gardner Denver Holdings, Inc. (a)		3,562,444	$	116,812,527

Construction - 2.6%
Masco Corp.		3,859,349	$	159,468,301
Sherwin-Williams Co.		984,130		508,549,177
Stanley Black & Decker, Inc.		3,550,354		510,185,870

			$	1,178,203,348
Consumer Products - 1.2%
Colgate-Palmolive Co.		1,385,747	$	93,634,925
Kimberly-Clark Corp.		1,266,130		166,103,595
Procter & Gamble Co.		901,357		102,060,653
Reckitt Benckiser Group PLC		2,696,822		199,063,377

			$	560,862,550
Electrical Equipment - 1.0%
Johnson Controls International PLC		13,175,902	$	481,842,736

Electronics - 3.4%
Analog Devices, Inc.		2,781,428	$	303,314,723
NXP Semiconductors N.V.		2,689,365		305,753,907
Texas Instruments, Inc.		8,588,346		980,273,813

			$	1,589,342,443
Energy - Independent - 1.7%
ConocoPhillips		6,616,690	$	320,380,130
EOG Resources, Inc.		4,418,426		279,509,629
Pioneer Natural Resources Co.		1,332,661		163,624,117

			$	763,513,876
Energy - Integrated - 1.5%
Chevron Corp.		3,161,761	$	295,118,772
Suncor Energy, Inc.		14,246,731		392,614,326

			$	687,733,098
Food & Beverages - 3.7%
Archer Daniels Midland Co.		6,161,464	$	231,979,119
Danone S.A.		2,741,434		194,078,358
J.M. Smucker Co.		1,633,323		168,215,936
Nestle S.A.		8,007,632		829,646,342
PepsiCo, Inc.		2,023,191		267,121,908

			$	1,691,041,663

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Health Maintenance Organizations - 2.2%
Cigna Corp.		5,580,296	$	1,020,859,350

Insurance - 8.2%
Aon PLC		5,787,585	$	1,203,817,680
Chubb Ltd.		6,901,740		1,000,959,352
Marsh & McLennan Cos., Inc.		7,353,380		768,869,413
Travelers Cos., Inc.		6,713,840		804,385,170

			$	3,778,031,615
Leisure & Toys - 0.1%
Harley-Davidson, Inc.		1,449,111	$	44,154,412

Machinery & Tools - 3.9%
Eaton Corp. PLC		6,554,834	$	594,654,540
Illinois Tool Works, Inc.		4,869,492		817,003,368
Ingersoll Rand, Inc. (a)		4,020,363		401,975,114

			$	1,813,633,022
Major Banks - 10.4%
Bank of New York Mellon Corp.		6,498,617	$	259,294,818
Goldman Sachs Group, Inc.		3,753,474		753,584,975
JPMorgan Chase & Co.		18,332,920		2,128,635,341
PNC Financial Services Group, Inc.		4,779,497		604,128,421
State Street Corp.		5,464,282		372,172,247
Wells Fargo & Co.		16,794,199		686,043,029

			$	4,803,858,831
Medical & Health Technology & Services - 0.7%
McKesson Corp.		2,460,001	$	344,055,740

Medical Equipment - 7.2%
Abbott Laboratories		7,678,587	$	591,481,556
Danaher Corp.		5,024,048		726,376,860
Medtronic PLC		13,189,981		1,327,835,387
Thermo Fisher Scientific, Inc.		2,251,966		654,871,713

			$	3,300,565,516
Other Banks & Diversified Financials - 7.3%
American Express Co.		3,918,763	$	430,789,617
Citigroup, Inc.		17,519,734		1,111,802,320
Moody’s Corp.		1,362,144		326,955,424
Truist Financial Corp.		13,617,923		628,330,967
U.S. Bancorp		19,081,380		886,139,287

			$	3,384,017,615

Portfolio of Investments (unaudited) – continued



Issuer	Shares/Par		Value ($)
Common Stocks - continued
Pharmaceuticals - 7.0%
Johnson & Johnson		11,956,587	$	1,607,921,820
Merck & Co., Inc.		6,452,387		493,994,749
Novartis AG		1,258,950		105,687,893
Pfizer, Inc.		23,869,199		797,708,631
Roche Holding AG		719,750		234,598,542

			$	3,239,911,635
Railroad & Shipping - 1.9%
Canadian National Railway Co.		3,142,966	$	266,869,243
Union Pacific Corp.		3,675,671		587,408,983

			$	854,278,226
Real Estate - 0.4%
Public Storage, Inc., REIT		812,405	$	169,890,134

Specialty Chemicals - 0.7%
Corteva, Inc.		2,022,847	$	55,021,439
DuPont de Nemours, Inc.		6,324,718		271,330,402

			$	326,351,841
Telephone Services - 0.5%
Verizon Communications, Inc.		3,961,301	$	214,544,062

Tobacco - 1.5%
Altria Group, Inc.		3,919,448	$	158,228,116
Philip Morris International, Inc.		6,491,575		531,465,245

			$	689,693,361
Utilities - Electric Power - 6.4%
Duke Energy Corp.		12,723,239	$	1,166,721,016
FirstEnergy Corp.		14,501,492		645,751,439
Southern Co.		15,056,216		908,793,198
Xcel Energy, Inc.		3,906,934		243,480,127

			$	2,964,745,780
Total Common Stocks (Identified Cost, $28,601,898,465)			$	45,320,108,199

Investment Companies (h) - 1.2%
Money Market Funds - 1.2%
MFS Institutional Money Market Portfolio, 1.61% (v) (Identified Cost, $539,882,345)		539,867,592	$	539,921,579

Other Assets, Less Liabilities - 0.4%			185,497,945
Net Assets - 100.0%			$	46,045,527,723

Portfolio of Investments (unaudited) – continued

(a)	Non-income producing security.

(h)

(v)	Affiliated issuer that is available only to investment companies managed by MFS. The rate quoted for the MFS Institutional Money Market Portfolio is the annualizedseven-day yield of the fund at period end.

The following abbreviations are used in this report and are defined:

REIT

Real Estate Investment Trust

See Notes to Financial Statements

Financial Statements

STATEMENT OF ASSETS AND LIABILITIES

At 2/29/20 (unaudited)

This statement represents your fund’s balance sheet, which details the assets and liabilities comprising the total value of the fund.


Assets
Investments in unaffiliated issuers, at value (identified cost, $28,601,898,465)			$45,320,108,199
Investments in affiliated issuers, at value (identified cost, $539,882,345)			539,921,579
Cash			3,781,648
Receivables for
Investments sold			387,763,495
Fund shares sold			135,966,999
Dividends			136,708,835
Other assets			123,219
Total assets			$46,524,373,974

Liabilities
Payables for
Distributions			$1,090
Investments purchased			320,082,701
Fund shares reacquired			138,931,137
Payable to affiliates
Investment adviser			1,692,405
Administrative services fee			4,666
Shareholder servicing costs			17,066,461
Distribution and service fees			258,288
Program manager fees			138
Payable for independent Trustees’ compensation			16,375
Accrued expenses and other liabilities			792,990
Total liabilities			$478,846,251
Net assets			$46,045,527,723

Net assets consist of
Paid-in capital			$29,076,747,325
Total distributable earnings (loss)			16,968,780,398
Net assets			$46,045,527,723
Shares of beneficial interest outstanding			1,157,845,908

Statement of Assets and Liabilities (unaudited) – continued



	Net assets		Shares outstanding		Net asset value per share (a)
Class A		$6,321,147,834		159,293,235		$39.68
Class B		68,907,847		1,746,055		39.46
Class C		790,794,786		20,187,206		39.17
Class I		19,494,984,071		488,256,803		39.93
Class R1		18,567,554		477,918		38.85
Class R2		369,749,323		9,420,896		39.25
Class R3		1,979,607,917		50,092,750		39.52
Class R4		2,423,846,422		61,071,034		39.69
Class R6		14,545,313,565		366,468,617		39.69
Class 529A		27,161,232		690,524		39.33
Class 529B		552,199		14,192		38.91
Class 529C		4,894,973		126,678		38.64

(a)

Maximum offering price per share was equal to the net asset value per share for all share classes, except for Classes A and 529A, for which the maximum offering prices per share were $42.10 [100 / 94.25 x $39.68] and $41.73 [100 / 94.25 x $39.33], respectively. On sales of $50,000 or more, the maximum offering prices of Class A and Class 529A shares are reduced. A contingent deferred sales charge may be imposed on redemptions of Class A, Class B, Class C, Class 529B, and Class 529C shares. Redemption price per share was equal to the net asset value per share for Classes I, R1, R2, R3, R4, R6, and 529A.

See Notes to Financial Statements

Financial Statements

STATEMENT OF OPERATIONS

Six months ended 2/29/20 (unaudited)

This statement describes how much your fund earned in investment income and accrued in expenses. It also describes any gains and/or losses generated by fund operations.


Net investment income (loss)
Income
Dividends	$558,671,430
Dividends from affiliated issuers	4,334,245
Income on securities loaned	1,442,310
Other	290,009
Interest	54
Foreign taxes withheld	(1,174,903	)
Total investment income	$563,563,145
Expenses
Management fee	$113,127,639
Distribution and service fees	17,422,823
Shareholder servicing costs	18,283,215
Program manager fees	8,719
Administrative services fee	275,671
Independent Trustees’ compensation	111,536
Custodian fee	343,045
Shareholder communications	857,509
Audit and tax fees	35,844
Legal fees	207,974
Miscellaneous	595,837
Total expenses	$151,269,812
Reduction of expenses by investment adviser and distributor	(2,585,436	)
Net expenses	$148,684,376
Net investment income (loss)	$414,878,769

Realized and unrealized gain (loss)
Realized gain (loss) (identified cost basis)
Unaffiliated issuers	$268,757,253
Affiliated issuers	(46,442	)
Foreign currency	134,286
Net realized gain (loss)	$268,845,097
Change in unrealized appreciation or depreciation
Unaffiliated issuers	$(1,537,444,159	)
Affiliated issuers	(4,442	)
Translation of assets and liabilities in foreign currencies	413,824
Net unrealized gain (loss)	$(1,537,034,777	)
Net realized and unrealized gain (loss)	$(1,268,189,680	)
Change in net assets from operations	$(853,310,911	)

See Notes to Financial Statements

Financial Statements

STATEMENTS OF CHANGES IN NET ASSETS

These statements describe the increases and/or decreases in net assets resulting from operations, any distributions, and any shareholder transactions.


Change in net assets	Six months ended 2/29/20 (unaudited)			Year ended 8/31/19

From operations
Net investment income (loss)		$414,878,769			$1,023,614,003
Net realized gain (loss)		268,845,097			748,154,368
Net unrealized gain (loss)		(1,537,034,777	)		492,230,726
Change in net assets from operations		$(853,310,911	)		$2,263,999,097
Total distributions to shareholders		$(1,051,822,355	)		$(1,629,458,929	)
Change in net assets from fund share transactions		$166,569,626			$(1,485,669,529	)
Total change in net assets		$(1,738,563,640	)		$(851,129,361	)

Net assets
At beginning of period		47,784,091,363			48,635,220,724
At end of period		$46,045,527,723			$47,784,091,363

See Notes to Financial Statements

Financial Statements

FINANCIAL HIGHLIGHTS


	Six months ended 2/29/20			Year ended
Class A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.31			$40.82			$39.00			$35.93			$33.38			$34.70

Income (loss) from investment operations
Net investment income (loss) (d)		$0.31			$0.79			$0.59			$0.66	(c)		$0.54			$0.63
Net realized and unrealized gain (loss)		(1.07	)		1.03			3.04			3.65			3.81			(0.36	)
Total from investment operations		$(0.76	)		$1.82			$3.63			$4.31			$4.35			$0.27

Less distributions declared to shareholders
From net investment income		$(0.32	)		$(0.79	)		$(0.60	)		$(0.62	)		$(0.56	)		$(0.67	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.87	)		$(1.33	)		$(1.81	)		$(1.24	)		$(1.80	)		$(1.59	)
Net asset value, end of period (x)		$39.68			$41.31			$40.82			$39.00			$35.93			$33.38
Total return (%) (r)(s)(t)(x)		(2.03	)(n)		4.85			9.42			12.24	(c)		13.55			0.68

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.82	(a)		0.83			0.82			0.86	(c)		0.90			0.90
Expenses after expense reductions (f)		0.81	(a)		0.82			0.81			0.84	(c)		0.86			0.86
Net investment income (loss)		1.45	(a)		2.00			1.46			1.77	(c)		1.60			1.80
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$6,321,148			$6,520,132			$6,736,296			$6,344,965			$9,033,842			$8,478,761

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.09			$40.59			$38.76			$35.72			$33.19			$34.50

Income (loss) from investment operations
Net investment income (loss) (d)		$0.15			$0.49			$0.28			$0.37	(c)		$0.28			$0.37
Net realized and unrealized gain (loss)		(1.08	)		1.03			3.04			3.64			3.79			(0.35	)
Total from investment operations		$(0.93	)		$1.52			$3.32			$4.01			$4.07			$0.02

Less distributions declared to shareholders
From net investment income		$(0.15	)		$(0.48	)		$(0.28	)		$(0.35	)		$(0.30	)		$(0.41	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.70	)		$(1.02	)		$(1.49	)		$(0.97	)		$(1.54	)		$(1.33	)
Net asset value, end of period (x)		$39.46			$41.09			$40.59			$38.76			$35.72			$33.19
Total return (%) (r)(s)(t)(x)		(2.42	)(n)		4.08			8.62			11.40	(c)		12.68			(0.06	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.57	(a)		1.58			1.57			1.61	(c)		1.65			1.65
Expenses after expense reductions (f)		1.56	(a)		1.57			1.56			1.59	(c)		1.61			1.61
Net investment income (loss)		0.69	(a)		1.24			0.71			0.99	(c)		0.85			1.05
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$68,908			$84,737			$111,494			$137,361			$154,742			$154,205

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.80			$40.31			$38.52			$35.50			$33.00			$34.33

Income (loss) from investment operations
Net investment income (loss) (d)		$0.15			$0.49			$0.28			$0.37	(c)		$0.28			$0.37
Net realized and unrealized gain (loss)		(1.07	)		1.03			3.01			3.62			3.77			(0.36	)
Total from investment operations		$(0.92	)		$1.52			$3.29			$3.99			$4.05			$0.01

Less distributions declared to shareholders
From net investment income		$(0.16	)		$(0.49	)		$(0.29	)		$(0.35	)		$(0.31	)		$(0.42	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.71	)		$(1.03	)		$(1.50	)		$(0.97	)		$(1.55	)		$(1.34	)
Net asset value, end of period (x)		$39.17			$40.80			$40.31			$38.52			$35.50			$33.00
Total return (%) (r)(s)(t)(x)		(2.42	)(n)		4.10			8.58			11.43	(c)		12.69			(0.09	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.57	(a)		1.58			1.57			1.61	(c)		1.65			1.65
Expenses after expense reductions (f)		1.56	(a)		1.57			1.56			1.59	(c)		1.61			1.61
Net investment income (loss)		0.69	(a)		1.24			0.71			0.99	(c)		0.85			1.06
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$790,795			$881,020			$1,050,477			$1,389,685			$1,538,605			$1,335,968

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class I	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.56			$41.06			$39.22			$36.13			$33.56			$34.88

Income (loss) from investment operations
Net investment income (loss) (d)		$0.37			$0.90			$0.70			$0.74	(c)		$0.63			$0.72
Net realized and unrealized gain (loss)		(1.08	)		1.02			3.05			3.70			3.82			(0.36	)
Total from investment operations		$(0.71	)		$1.92			$3.75			$4.44			$4.45			$0.36

Less distributions declared to shareholders
From net investment income		$(0.37	)		$(0.88	)		$(0.70	)		$(0.73	)		$(0.64	)		$(0.76	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.92	)		$(1.42	)		$(1.91	)		$(1.35	)		$(1.88	)		$(1.68	)
Net asset value, end of period (x)		$39.93			$41.56			$41.06			$39.22			$36.13			$33.56
Total return (%) (r)(s)(t)(x)		(1.90	)(n)		5.11			9.69			12.54	(c)		13.83			0.93

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.57	(a)		0.58			0.57			0.61	(c)		0.65			0.65
Expenses after expense reductions (f)		0.56	(a)		0.57			0.57			0.59	(c)		0.61			0.61
Net investment income (loss)		1.70	(a)		2.25			1.72			1.98	(c)		1.84			2.06
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$19,494,984			$20,076,773			$20,727,676			$19,624,016			$17,134,836			$13,888,395

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R1	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.47			$40.01			$38.25			$35.27			$32.79			$34.11

Income (loss) from investment operations
Net investment income (loss) (d)		$0.15			$0.48			$0.28			$0.36	(c)		$0.28			$0.36
Net realized and unrealized gain (loss)		(1.06	)		1.02			2.99			3.60			3.74			(0.34	)
Total from investment operations		$(0.91	)		$1.50			$3.27			$3.96			$4.02			$0.02

Less distributions declared to shareholders
From net investment income		$(0.16	)		$(0.50	)		$(0.30	)		$(0.36	)		$(0.30	)		$(0.42	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.71	)		$(1.04	)		$(1.51	)		$(0.98	)		$(1.54	)		$(1.34	)
Net asset value, end of period (x)		$38.85			$40.47			$40.01			$38.25			$35.27			$32.79
Total return (%) (r)(s)(t)(x)		(2.42	)(n)		4.08			8.61			11.40	(c)		12.69			(0.07	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.57	(a)		1.58			1.57			1.61	(c)		1.65			1.65
Expenses after expense reductions (f)		1.56	(a)		1.57			1.56			1.59	(c)		1.61			1.61
Net investment income (loss)		0.69	(a)		1.24			0.72			0.99	(c)		0.85			1.06
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$18,568			$21,820			$24,791			$26,663			$27,096			$27,860

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R2	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.87			$40.39			$38.60			$35.59			$33.08			$34.40

Income (loss) from investment operations
Net investment income (loss) (d)		$0.25			$0.68			$0.48			$0.55	(c)		$0.45			$0.54
Net realized and unrealized gain (loss)		(1.06	)		1.03			3.02			3.62			3.78			(0.35	)
Total from investment operations		$(0.81	)		$1.71			$3.50			$4.17			$4.23			$0.19

Less distributions declared to shareholders
From net investment income		$(0.26	)		$(0.69	)		$(0.50	)		$(0.54	)		$(0.48	)		$(0.59	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.81	)		$(1.23	)		$(1.71	)		$(1.16	)		$(1.72	)		$(1.51	)
Net asset value, end of period (x)		$39.25			$40.87			$40.39			$38.60			$35.59			$33.08
Total return (%) (r)(s)(t)(x)		(2.15	)(n)		4.60			9.15			11.95	(c)		13.27			0.43

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.07	(a)		1.08			1.07			1.11	(c)		1.15			1.15
Expenses after expense reductions (f)		1.06	(a)		1.07			1.07			1.09	(c)		1.11			1.11
Net investment income (loss)		1.19	(a)		1.73			1.21			1.49	(c)		1.35			1.54
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$369,749			$437,221			$550,200			$614,044			$567,665			$521,592

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R3	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.15			$40.66			$38.85			$35.81			$33.28			$34.60

Income (loss) from investment operations
Net investment income (loss) (d)		$0.31			$0.79			$0.59			$0.65	(c)		$0.54			$0.63
Net realized and unrealized gain (loss)		(1.07	)		1.03			3.03			3.64			3.79			(0.35	)
Total from investment operations		$(0.76	)		$1.82			$3.62			$4.29			$4.33			$0.28

Less distributions declared to shareholders
From net investment income		$(0.32	)		$(0.79	)		$(0.60	)		$(0.63	)		$(0.56	)		$(0.68	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.87	)		$(1.33	)		$(1.81	)		$(1.25	)		$(1.80	)		$(1.60	)
Net asset value, end of period (x)		$39.52			$41.15			$40.66			$38.85			$35.81			$33.28
Total return (%) (r)(s)(t)(x)		(2.04	)(n)		4.87			9.43			12.23	(c)		13.54			0.69

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.82	(a)		0.83			0.82			0.86	(c)		0.90			0.90
Expenses after expense reductions (f)		0.81	(a)		0.82			0.82			0.84	(c)		0.86			0.86
Net investment income (loss)		1.44	(a)		1.99			1.47			1.74	(c)		1.60			1.80
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$1,979,608			$2,096,743			$2,259,562			$2,030,023			$1,903,910			$1,571,281

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R4	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.32			$40.82			$39.00			$35.94			$33.40			$34.72

Income (loss) from investment operations
Net investment income (loss) (d)		$0.36			$0.89			$0.69			$0.74	(c)		$0.62			$0.72
Net realized and unrealized gain (loss)		(1.07	)		1.03			3.04			3.67			3.80			(0.36	)
Total from investment operations		$(0.71	)		$1.92			$3.73			$4.41			$4.42			$0.36

Less distributions declared to shareholders
From net investment income		$(0.37	)		$(0.88	)		$(0.70	)		$(0.73	)		$(0.64	)		$(0.76	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.92	)		$(1.42	)		$(1.91	)		$(1.35	)		$(1.88	)		$(1.68	)
Net asset value, end of period (x)		$39.69			$41.32			$40.82			$39.00			$35.94			$33.40
Total return (%) (r)(s)(t)(x)		(1.91	)(n)		5.14			9.70			12.52	(c)		13.80			0.93

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.57	(a)		0.58			0.57			0.61	(c)		0.65			0.65
Expenses after expense reductions (f)		0.56	(a)		0.57			0.57			0.59	(c)		0.61			0.61
Net investment income (loss)		1.69	(a)		2.24			1.72			1.99	(c)		1.85			2.05
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$2,423,846			$2,916,674			$3,201,331			$3,060,883			$3,233,421			$2,787,041

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class R6	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$41.32			$40.83			$39.01			$35.94			$33.40			$34.72

Income (loss) from investment operations
Net investment income (loss) (d)		$0.39			$0.93			$0.73			$0.76	(c)		$0.66			$0.76
Net realized and unrealized gain (loss)		(1.08	)		1.02			3.04			3.69			3.80			(0.36	)
Total from investment operations		$(0.69	)		$1.95			$3.77			$4.45			$4.46			$0.40

Less distributions declared to shareholders
From net investment income		$(0.39	)		$(0.92	)		$(0.74	)		$(0.76	)		$(0.68	)		$(0.80	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.94	)		$(1.46	)		$(1.95	)		$(1.38	)		$(1.92	)		$(1.72	)
Net asset value, end of period (x)		$39.69			$41.32			$40.83			$39.01			$35.94			$33.40
Total return (%) (r)(s)(t)(x)		(1.86	)(n)		5.22			9.81			12.66	(c)		13.93			1.04

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.46	(a)		0.48			0.47			0.51	(c)		0.54			0.54
Expenses after expense reductions (f)		0.45	(a)		0.47			0.47			0.49	(c)		0.50			0.50
Net investment income (loss)		1.80	(a)		2.35			1.83			2.04	(c)		1.95			2.17
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$14,545,314			$14,716,194			$13,941,823			$10,957,734			$6,218,954			$4,846,172

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529A	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.96			$40.48			$38.69			$35.67			$33.15			$34.48

Income (loss) from investment operations
Net investment income (loss) (d)		$0.30			$0.78			$0.58			$0.63	(c)		$0.53			$0.63
Net realized and unrealized gain (loss)		(1.07	)		1.02			3.02			3.64			3.79			(0.36	)
Total from investment operations		$(0.77	)		$1.80			$3.60			$4.27			$4.32			$0.27

Less distributions declared to shareholders
From net investment income		$(0.31	)		$(0.78	)		$(0.60	)		$(0.63	)		$(0.56	)		$(0.68	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.86	)		$(1.32	)		$(1.81	)		$(1.25	)		$(1.80	)		$(1.60	)
Net asset value, end of period (x)		$39.33			$40.96			$40.48			$38.69			$35.67			$33.15
Total return (%) (r)(s)(t)(x)		(2.06	)(n)		4.85			9.40			12.21	(c)		13.55			0.67

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.87	(a)		0.88			0.89			0.96	(c)		1.00			1.00
Expenses after expense reductions (f)		0.83	(a)		0.84			0.83			0.85	(c)		0.86			0.86
Net investment income (loss)		1.42	(a)		1.98			1.45			1.71	(c)		1.59			1.82
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$27,161			$27,149			$25,416			$22,490			$18,625			$16,543

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529B	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.46			$40.05			$38.23			$35.27			$32.78			$34.08

Income (loss) from investment operations
Net investment income (loss) (d)		$0.27			$0.63			$0.43			$0.47	(c)		$0.29			$0.47
Net realized and unrealized gain (loss)		(1.06	)		1.00			3.00			3.61			3.73			(0.34	)
Total from investment operations		$(0.79	)		$1.63			$3.43			$4.08			$4.02			$0.13

Less distributions declared to shareholders
From net investment income		$(0.21	)		$(0.68	)		$(0.40	)		$(0.50	)		$(0.29	)		$(0.51	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.76	)		$(1.22	)		$(1.61	)		$(1.12	)		$(1.53	)		$(1.43	)
Net asset value, end of period (x)		$38.91			$40.46			$40.05			$38.23			$35.27			$32.78
Total return (%) (r)(s)(t)(x)		(2.13	)(n)		4.46			9.05			11.78	(c)		12.70			0.27

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		0.99	(a)		1.22			1.22			1.34	(c)		1.68			1.37
Expenses after expense reductions (f)		0.98	(a)		1.20			1.19			1.26	(c)		1.58			1.27
Net investment income (loss)		1.26	(a)		1.61			1.10			1.28	(c)		0.87			1.38
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$552			$680			$835			$908			$941			$888

See Notes to Financial Statements

Financial Highlights – continued


	Six months ended 2/29/20			Year ended
Class 529C	Six months ended 2/29/20			8/31/19			8/31/18			8/31/17			8/31/16			8/31/15
	(unaudited)
Net asset value, beginning of period		$40.26			$39.81			$38.07			$35.11			$32.66			$34.00

Income (loss) from investment operations
Net investment income (loss) (d)		$0.14			$0.46			$0.26			$0.34	(c)		$0.26			$0.35
Net realized and unrealized gain (loss)		(1.05	)		1.01			2.97			3.59			3.73			(0.36	)
Total from investment operations		$(0.91	)		$1.47			$3.23			$3.93			$3.99			$(0.01	)

Less distributions declared to shareholders
From net investment income		$(0.16	)		$(0.48	)		$(0.28	)		$(0.35	)		$(0.30	)		$(0.41	)
From net realized gain		(0.55	)		(0.54	)		(1.21	)		(0.62	)		(1.24	)		(0.92	)
Total distributions declared to shareholders		$(0.71	)		$(1.02	)		$(1.49	)		$(0.97	)		$(1.54	)		$(1.33	)
Net asset value, end of period (x)		$38.64			$40.26			$39.81			$38.07			$35.11			$32.66
Total return (%) (r)(s)(t)(x)		(2.43	)(n)		4.04			8.54			11.38	(c)		12.64			(0.14	)

Ratios (%) (to average net assets) and Supplemental data:
Expenses before expense reductions (f)		1.62	(a)		1.63			1.64			1.71	(c)		1.75			1.75
Expenses after expense reductions (f)		1.61	(a)		1.61			1.61			1.63	(c)		1.65			1.66
Net investment income (loss)		0.65	(a)		1.19			0.67			0.93	(c)		0.80			1.03
Portfolio turnover		7	(n)		11			11			14			12			12
Net assets at end of period (000 omitted)		$4,895			$4,947			$5,320			$5,924			$5,381			$4,434

See Notes to Financial Statements

Financial Highlights – continued

(a)	Annualized.

(c)	Amount reflects aone-time reimbursement of expenses by the custodian (or former custodian) without which net investment income and performance would be lower and expenses would be higher.

(d)	Per share data is based on average shares outstanding.

(f)	Ratios do not reflect reductions from fees paid indirectly, if applicable.

(n)	Not annualized.

(r)	Certain expenses have been reduced without which performance would have been lower.

(s)	From time to time the fund may receive proceeds from litigation settlements, without which performance would be lower.

(t)	Total returns do not include any applicable sales charges.

(x)	The net asset values and total returns have been calculated on net assets which include adjustments made in accordance with U.S. generally accepted accounting principles required at period end for financial reporting purposes.

See Notes to Financial Statements

NOTES TO FINANCIAL STATEMENTS

(unaudited)

(1) Business and Organization

MFS Value Fund (the fund) is a diversified series of MFS Series Trust I (the trust). The trust is organized as a Massachusetts business trust and is registered under the Investment Company Act of 1940, as amended, as anopen-end management investment company.

(2) Significant Accounting Policies

Investment Valuations– Equity securities, including restricted equity securities, are generally valued at the last sale or official closing price on their primary market or

Notes to Financial Statements (unaudited) – continued

Various inputs are used in determining the value of the fund’s assets or liabilities. These inputs are categorized into three broad levels. In certain cases, the inputs used to

Notes to Financial Statements (unaudited) – continued

measure fair value may fall into different levels of the fair value hierarchy. In such cases, an investment’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The fund’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment, and considers factors specific to the investment. Level 1 includes unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 includes other significant observable market-based inputs (including quoted prices for similar securities, interest rates, prepayment speed, and credit risk). Level 3 includes unobservable inputs, which may include the adviser’s own assumptions in determining the fair value of investments. The following is a summary of the levels used as of February 29, 2020 in valuing the fund’s assets or liabilities:



Financial Instruments	Level 1		Level 2		Level 3		Total
Equity Securities:
United States		$41,716,444,996		$401,975,114		$—		$42,118,420,110
Switzerland		—		1,169,932,777		—		1,169,932,777
United Kingdom		—		872,439,478		—		872,439,478
Canada		659,483,569		—		—		659,483,569
Netherlands		305,753,907		—		—		305,753,907
France		—		194,078,358		—		194,078,358
Mutual Funds		539,921,579		—		—		539,921,579
Total		$43,221,604,051		$2,638,425,727		$—		$45,860,029,778

For further information regarding security characteristics, see the Portfolio of Investments.

Notes to Financial Statements (unaudited) – continued

the fund with indemnification against Borrower default. In the event of Borrower default, the lending agent will, for the benefit of the fund, either purchase securities identical to those loaned or, when such purchase is commercially impracticable, pay the fund the market value of the loaned securities. In return, the lending agent assumes the fund’s rights to the related collateral. If the collateral value is less than the cost to purchase identical securities, the lending agent is responsible for the shortfall, but only to the extent that such shortfall is not due to a decline in collateral value resulting from collateral reinvestment for which the fund bears the risk of loss. A portion of the income generated upon investment of the collateral is remitted to the Borrowers, and the remainder is allocated between the fund and the lending agent. On loans collateralized by U.S. Treasury and/or federal agency obligations, a fee is received from the Borrower, and is allocated between the fund and the lending agent. Income from securities lending is separately reported in the Statement of Operations. The dividend and interest income earned on the securities loaned is accounted for in the same manner as other dividend and interest income. At February 29, 2020, there were no securities on loan or collateral outstanding.

Investment Transactions and Income– Investment transactions are recorded on the trade date. Dividends received in cash are recorded on theex-dividend date. Certain dividends from foreign securities will be recorded when the fund is informed of the dividend if such information is obtained subsequent to theex-dividend date. Dividend and interest payments received in additional securities are recorded on theex-dividend orex-interest date in an amount equal to the value of the security on such date.

Notes to Financial Statements (unaudited) – continued

in which the fund invests. Additionally, capital gains realized by the fund on securities issued in or by certain foreign countries may be subject to capital gains tax imposed by those countries.

Book/tax differences primarily relate to wash sale loss deferrals, treating a portion of the proceeds from redemptions as a distribution for tax purposes, and redemptionsin-kind.



	Year ended 8/31/19
Ordinary income (including any short-term capital gains)		$1,031,454,957
Long-term capital gains		598,003,972

Total distributions		$1,629,458,929

The federal tax cost and the tax basis components of distributable earnings were as follows:



As of 2/29/20

Cost of investments	$29,320,102,748
Gross appreciation	17,090,005,789

Gross depreciation	(550,078,759	)
Net unrealized appreciation (depreciation)	$16,539,927,030

As of 8/31/19

Undistributed ordinary income	144,928,850
Undistributed long-term capital gain	636,255,955
Other temporary differences	(19,045	)
Net unrealized appreciation (depreciation)	18,092,747,904

The aggregate cost above includes prior fiscal year end tax adjustments, if applicable.

Multiple Classes of Shares of Beneficial Interest– The fund offers multiple classes of shares, which differ in their respective distribution, service, and program manager fees. The fund’s income, realized and unrealized gain (loss), and common expenses are allocated to shareholders based on the daily net assets of each class. Dividends are declared separately for each class. Differences in per share dividend rates are generally due to differences in separate class expenses. Class B and Class 529B shares will

Notes to Financial Statements (unaudited) – continued

convert to Class A and Class 529A shares, respectively, approximately eight years after purchase. Class C and Class 529C shares will convert to Class A and Class 529A shares, respectively, approximately ten years after purchase. The fund’s distributions declared to shareholders as reported in the Statements of Changes in Net Assets are presented by class as follows:


	Six months ended 2/29/20		Year ended 8/31/19
Class A		$137,026,527		$212,127,405
Class B		1,351,042		2,506,594
Class C		14,673,978		24,795,233
Class I		441,950,374		694,992,844
Class R1		352,923		603,582
Class R2		8,167,311		14,982,779
Class R3		44,639,775		70,153,680
Class R4		62,567,628		105,158,843
Class R6		340,412,315		503,130,979
Class 529A		578,650		852,206
Class 529B		12,135		24,362
Class 529C		89,697		130,422
Total		$1,051,822,355		$1,629,458,929

(3) Transactions with Affiliates


Up to $7.5 billion	0.60	%
In excess of $7.5 billion and up to $10 billion	0.53	%
In excess of $10 billion and up to $20 billion	0.50	%
In excess of $20 billion and up to $25 billion	0.45	%
In excess of $25 billion and up to $30 billion	0.42	%
In excess of $30 billion and up to $35 billion	0.40	%
In excess of $35 billion and up to $40 billion	0.38	%
In excess of $40 billion and up to $45 billion	0.36	%
In excess of $45 billion and up to $50 billion	0.35	%
In excess of $50 billion and up to $60 billion	0.34	%
In excess of $60 billion	0.33	%

MFS has agreed in writing to reduce its management fee by a specified amount if certain MFS mutual fund assets exceed thresholds agreed to by MFS and the fund’s Board of Trustees. For the six months ended February 29, 2020, this management fee reduction amounted to $2,540,281, which is included in the reduction of total expenses in the Statement of Operations. The management fee incurred for the six months ended February 29, 2020 was equivalent to an annual effective rate of 0.44% of the fund’s average daily net assets.

Notes to Financial Statements (unaudited) – continued

Distributor– MFS Fund Distributors, Inc. (MFD), a wholly-owned subsidiary of MFS, as distributor, received $691,314 and $7,617 for the six months ended February 29, 2020, as its portion of the initial sales charge on sales of Class A and Class 529A shares of the fund, respectively.

The Board of Trustees has adopted a distribution plan for certain share classes pursuant to Rule12b-1 of the Investment Company Act of 1940.

Distribution Plan Fee Table:



	Distribution Fee Rate (d)		Service Fee Rate (d)		Total Distribution Plan (d)		Annual Effective Rate (e)		Distribution and Service Fee
Class A		—		0.25%		0.25%		0.25%		$8,565,641
Class B		0.75%		0.25%		1.00%		1.00%		414,894
Class C		0.75%		0.25%		1.00%		1.00%		4,441,947
Class R1		0.75%		0.25%		1.00%		1.00%		106,723
Class R2		0.25%		0.25%		0.50%		0.50%		1,075,962
Class R3		—		0.25%		0.25%		0.25%		2,753,730
Class 529A		—		0.25%		0.25%		0.22%		36,116
Class 529B		0.75%		0.25%		1.00%		0.37%		1,271
Class 529C		0.75%		0.25%		1.00%		1.00%		26,539
Total Distribution and Service Fees										$17,422,823

(d)

(e)

The annual effective rates represent actual fees incurred under the distribution plan for the six months ended February 29, 2020 based on each class’s average daily net assets. MFD has voluntarily agreed to rebate a portion of each class’s 0.25% service fee attributable to accounts for which MFD retains the 0.25% service fee except for accounts attributable to MFS or its affiliates’ seed money. For the six months ended February 29, 2020, this rebate amounted to $39,040, $591, $978, $22, $324, $153, $4,013, $12, and $22 for Class A, Class B, Class C, Class R1, Class R2, Class R3, Class 529A, Class 529B, and Class 529C, respectively, and is included in the reduction of total expenses in the Statement of Operations. For the period from October 1, 2019 through February 29, 2020, the 0.75% distribution fee was not imposed for Class 529B shares due to the sales charge limitations contained in Financial Industry Regulatory Authority (“FINRA”) Rule 2341.

Notes to Financial Statements (unaudited) – continued

the event of a shareholder redemption within 12 months of purchase. All contingent deferred sales charges are paid to MFD and during the six months ended February 29, 2020, were as follows:



	Amount
Class A		$24,151
Class B		24,132
Class C		16,046
Class 529B		8
Class 529C		62



	Fee
Class 529A		$7,223
Class 529B		169
Class 529C		1,327
Total Program Manager Fees		$8,719

Shareholder Servicing Agent– MFS Service Center, Inc. (MFSC), a wholly-owned subsidiary of MFS, receives a fee from the fund for its services as shareholder servicing agent calculated as a percentage of the average daily net assets of the fund as determined periodically under the supervision of the fund’s Board of Trustees. For the six months ended February 29, 2020, the fee was $371,673, which equated to 0.0015% annually of the fund’s average daily net assets. MFSC also receives payment from the fund forout-of-pocket expenses,sub-accounting and other shareholder servicing costs which may be paid to affiliated and unaffiliated service providers. Class R6 shares do not incursub-accounting fees. For the six months ended February 29, 2020, theseout-of-pocket expenses,sub-accounting and other shareholder servicing costs amounted to $17,911,542.

Notes to Financial Statements (unaudited) – continued

The fund is permitted to engage in purchase and sale transactions with funds and accounts for which MFS serves as investment adviser orsub-adviser (“cross-trades”) pursuant to a policy adopted by the Board of Trustees. This policy has been designed to ensure that cross-trades conducted by the fund comply with Rule17a-7 under the Investment Company Act of 1940. During the six months ended February 29, 2020, the fund engaged in sale transactions pursuant to this policy, which amounted to $19,211,977. The sales transactions resulted in net realized gains of $8,531,011.

The adviser has voluntarily undertaken to reimburse the fund from its own resources on a quarterly basis for the cost of investment research embedded in the cost of the fund’s securities trades. This agreement may be rescinded at any time. For the six months ended February 29, 2020, this reimbursement amounted to $290,009, which is included in “Other” income in the Statement of Operations.

(4) Portfolio Securities

For the six months ended February 29, 2020, purchases and sales of investments, other than short-term obligations, aggregated $3,206,010,306 and $3,754,155,530, respectively.

(5) Shares of Beneficial Interest

The fund’s Declaration of Trust permits the Trustees to issue an unlimited number of full and fractional shares of beneficial interest. Transactions in fund shares were as follows:


	Six months ended 2/29/20				Year ended 8/31/19

	Shares		Amount		Shares		Amount
Shares sold
Class A		13,849,647		$599,938,409		24,411,847		$961,411,776
Class B		9,113		397,684		109,994		4,271,448
Class C		1,581,397		67,723,419		2,602,286		100,772,015
Class I		53,544,160		2,339,006,761		101,624,206		4,014,273,147
Class R1		37,195		1,588,182		105,084		4,054,356
Class R2		541,333		23,261,470		1,393,443		54,090,884
Class R3		5,645,577		242,787,118		8,683,642		336,653,144
Class R4		5,467,308		238,743,014		10,512,327		416,155,664
Class R6		40,348,553		1,756,904,319		74,625,324		2,951,676,391
Class 529A		51,172		2,209,861		100,457		3,921,061
Class 529B		477		20,562		954		37,532
Class 529C		13,299		561,214		20,871		805,355
		121,089,231		$5,273,142,013		224,190,435		$8,848,122,773

Notes to Financial Statements (unaudited) – continued


	Six months ended 2/29/20						Year ended 8/31/19

	Shares			Amount			Shares			Amount
Shares issued to shareholders in reinvestment of distributions
Class A		2,561,681			$111,977,228			4,662,710			$173,102,129
Class B		29,007			1,267,596			64,869			2,361,216
Class C		252,196			10,936,662			522,160			18,897,156
Class I		8,060,188			353,953,947			14,708,512			550,689,358
Class R1		8,209			352,923			16,758			603,573
Class R2		183,798			7,956,327			389,696			14,250,967
Class R3		1,025,207			44,637,165			1,897,634			70,152,285
Class R4		1,398,967			61,059,046			2,733,062			101,624,334
Class R6		7,117,548			310,627,037			12,268,131			457,296,101
Class 529A		13,351			578,650			23,109			851,636
Class 529B		282			12,135			675			24,362
Class 529C		2,096			89,697			3,642			130,422
		20,652,530			$903,448,413			37,290,958			$1,389,983,539

Shares reacquired
Class A		(14,933,487	)		$(647,470,846	)		(36,282,831	)		$(1,436,501,478	)
Class B		(354,393	)		(15,371,408	)		(859,557	)		(33,877,544	)
Class C		(3,242,535	)		(138,505,186	)		(7,585,556	)		(295,149,445	)
Class I		(56,381,853	)		(2,454,402,274	)		(138,135,941	)		(5,477,840,045	)
Class R1		(106,729	)		(4,512,436	)		(202,277	)		(7,851,973	)
Class R2		(2,002,061	)		(85,677,642	)		(4,707,159	)		(184,847,134	)
Class R3		(7,534,070	)		(326,041,558	)		(15,196,245	)		(597,739,263	)
Class R4		(16,385,031	)		(720,343,700	)		(21,071,772	)		(822,107,531	)
Class R6		(37,116,439	)		(1,615,461,718	)		(72,236,188	)		(2,862,769,021	)
Class 529A		(36,819	)		(1,593,651	)		(88,534	)		(3,526,656	)
Class 529B		(3,368	)		(145,306	)		(5,685	)		(222,222	)
Class 529C		(11,606	)		(495,075	)		(35,246	)		(1,343,529	)
		(138,108,391	)		$(6,010,020,800	)		(296,406,991	)		$(11,723,775,841	)

Net change
Class A		1,477,841			$64,444,791			(7,208,274	)		$(301,987,573	)
Class B		(316,273	)		(13,706,128	)		(684,694	)		(27,244,880	)
Class C		(1,408,942	)		(59,845,105	)		(4,461,110	)		(175,480,274	)
Class I		5,222,495			238,558,434			(21,803,223	)		(912,877,540	)
Class R1		(61,325	)		(2,571,331	)		(80,435	)		(3,194,044	)
Class R2		(1,276,930	)		(54,459,845	)		(2,924,020	)		(116,505,283	)
Class R3		(863,286	)		(38,617,275	)		(4,614,969	)		(190,933,834	)
Class R4		(9,518,756	)		(420,541,640	)		(7,826,383	)		(304,327,533	)
Class R6		10,349,662			452,069,638			14,657,267			546,203,471
Class 529A		27,704			1,194,860			35,032			1,246,041
Class 529B		(2,609	)		(112,609	)		(4,056	)		(160,328	)
Class 529C		3,789			155,836			(10,733	)		(407,752	)
		3,633,370			$166,569,626			(34,925,598	)		$(1,485,669,529	)

Notes to Financial Statements (unaudited) – continued

Class T shares were not publicly available for sale during the period. Please see the fund’s prospectus for details.

Effective June 1, 2019, purchases of the fund’s Class B and Class 529B shares are closed to new and existing investors subject to certain exceptions. Please see the fund’s prospectus for details.

The fund is one of several mutual funds in which certain MFS funds may invest. The MFS funds do not invest in the underlying funds for the purpose of exercising management or control. At the end of the period, the MFS Growth Allocation Fund was the owner of record of approximately 1% of the value of outstanding voting shares of the fund. In addition, the MFS Aggressive Growth Allocation Fund, the MFS Conservative Allocation Fund, the MFS Lifetime 2020 Fund, the MFS Lifetime 2025 Fund, the MFS Lifetime 2030 Fund, the MFS Lifetime 2035 Fund, the MFS Lifetime 2040 Fund, the MFS Lifetime 2045 Fund, the MFS Lifetime 2050 Fund, the MFS Lifetime 2055 Fund, the MFS Lifetime 2060 Fund, the MFS Lifetime Income Fund, the MFS Managed Wealth Fund, and the MFS Moderate Allocation Fund were each the owners of record of less than 1% of the value of outstanding voting shares of the fund.

(6) Line of Credit

The fund and certain other funds managed by MFS participate in a $1.25 billion unsecured committed line of credit, subject to a $1 billion sublimit, provided by a syndicate of banks under a credit agreement. Borrowings may be made for temporary financing needs. Interest is charged to each fund, based on its borrowings, generally at a rate equal to the highest of one month LIBOR, the Federal Funds Effective Rate and the Overnight Bank Funding Rate, plus an agreed upon spread. A commitment fee, based on the average daily, unused portion of the committed line of credit, is allocated among the participating funds. In addition, the fund and other funds managed by MFS have established unsecured uncommitted borrowing arrangements with certain banks for temporary financing needs. Interest is charged to each fund, based on its borrowings, at rates equal to customary reference rates plus an agreed upon spread. For the six months ended February 29, 2020, the fund’s commitment fee and interest expense were $128,393 and $0, respectively, and are included in “Miscellaneous” expense in the Statement of Operations.

(7) Investments in Affiliated Issuers



Affiliated Issuers	Beginning Value		Purchases		Sales Proceeds		Realized Gain (Loss)			Change in Unrealized Appreciation or Depreciation			Ending Value
MFS Institutional Money Market Portfolio		$453,132,119		$2,102,705,818		$2,015,865,474		$(46,442	)		$(4,442	)		$539,921,579

Affiliated Issuers										Dividend Income			Capital Gain Distributions
MFS Institutional Money Market Portfolio											$4,334,245			$—

Notes to Financial Statements (unaudited) – continued

(8) RedemptionsIn-Kind

On November 16, 2018, the fund recorded a redemptionin-kind of portfolio securities and cash that was valued at $96,466,346. The redeeming shareholder generally receives a pro rata share of the securities held by the fund. The distribution of such securities generated a realized gain of $51,529,296 for the fund, which is included in Net realized gain (loss) in the Statement of Operations. For tax purposes, no gains or losses were recognized.

(9) Impacts of COVID-19

PROXY VOTING POLICIES AND INFORMATION

QUARTERLY PORTFOLIO DISCLOSURE

FURTHER INFORMATION

INFORMATION ABOUT FUND CONTRACTS AND LEGAL CLAIMS

PROVISION OF FINANCIAL REPORTS AND SUMMARY PROSPECTUSES

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CONTACT

WEB SITE

mfs.com

MFS TALK

1-800-637-8255

24 hours a day

ACCOUNT SERVICE AND LITERATURE

Shareholders

1-800-225-2606

Financial advisors

1-800-343-2829

Retirement plan services

1-800-637-1255

MAILING ADDRESS

MFS Service Center, Inc.

P.O. Box 219341

Kansas City, MO 64121-9341

OVERNIGHT MAIL

MFS Service Center, Inc.

Suite 219341

430 W 7th Street

Kansas City, MO 64105-1407

ITEM 2.

CODE OF ETHICS.

During the period covered by this report, the Registrant has not amended any provision in its Code of Ethics (the “Code”) that relates to an element of the Code’s definitions enumerated in paragraph (b) of Item 2 of this FormN-CSR. During the period covered by this report, the Registrant did not grant a waiver, including an implicit waiver, from any provision of the Code.

ITEM 3.

AUDIT COMMITTEE FINANCIAL EXPERT.

Not applicable for semi-annual reports.

ITEM 4.

PRINCIPAL ACCOUNTANT FEES AND SERVICES.

Not applicable for semi-annual reports.

ITEM 5.

AUDIT COMMITTEE OF LISTED REGISTRANTS.

Not applicable to the Registrant.

ITEM 6.

INVESTMENTS

A schedule of investments for each series of the Registrant is included as part of the report to shareholders of such series under Item 1 of this FormN-CSR.

ITEM 7.

DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FORCLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 8.

PORTFOLIO MANAGERS OFCLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 9.

PURCHASES OF EQUITY SECURITIES BYCLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

Not applicable to the Registrant.

ITEM 10.

SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

There were no material changes to the procedures by which shareholders may send recommendations to the Board for nominees to the Registrant’s Board since the Registrant last provided disclosure as to such procedures in response to the requirements of Item 407 (c)(2)(iv) of RegulationS-K or this Item.

ITEM 11.

CONTROLS AND PROCEDURES.

(a)

Based upon their evaluation of the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule30a-3(c) under the Investment Company Act of 1940 (the “Act”)) as conducted within 90 days of the filing date of this report on FormN-CSR, the registrant’s principal financial officer and principal executive officer have concluded that those disclosure controls and procedures provide reasonable assurance that the material information required to be disclosed by the registrant on this report is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms.

(b)

There were no changes in the registrant’s internal controls over financial reporting (as defined in Rule30a-3(d) under the Act) that occurred during the period covered by the report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

ITEM 12.

DISCLOSURE OF SECURITIES LENDING ACTIVITIES FORCLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 13.

EXHIBITS.

(a)	File the exhibits listed below as part of this form. Letter or number the exhibits in the sequence indicated.

(1)

Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit. Not applicable.

(2)

A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule30a-2(a) under the Act (17 CFR270.30a-2): Attached hereto asEX-99.302CERT.

(3)

Any written solicitation to purchase securities under Rule23c-1 under the Act (17 CFR270.23c-1) sent or given during the period covered by the report by or on behalf of the registrant to 10 or more persons. Not applicable.

(4)

Change in the registrant’s independent public accountant. Not applicable.

(b)

If the report is filed under Section 13(a) or 15(d) of the Exchange Act, provide the certifications required by Rule30a-2(b) under the Act (17 CFR270.30a-2(b)), Rule13a-14(b) or Rule15d-14(b) under the Exchange Act (17 CFR240.13a-14(b) or240.15d-14(b)) and Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. 1350) as an exhibit. A certification furnished pursuant to this paragraph will not be deemed “filed” for the purposes of Section 18 of the Exchange Act (15 U.S.C. 78r),

or otherwise subject to the liability of that section. Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Exchange Act, except to the extent that the registrant specifically incorporates it by reference: Attached hereto asEX-99.906CERT.

Notice

A copy of the Amended and Restated Declaration of Trust, as amended, of the Registrant is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and the obligations of or arising out of this instrument are not binding upon any of the Trustees or shareholders individually, but are binding only upon the assets and property of the respective constituent series of the Registrant.

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.

(Registrant) MFS SERIES TRUST I


By (Signature and Title)*		DAVID L. DILORENZO
		David L. DiLorenzo, President

Date: April 16, 2020

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.


By (Signature and Title)*		DAVID L. DILORENZO
		David L. DiLorenzo, President (Principal Executive Officer)

Date: April 16, 2020


By (Signature and Title)*		JAMES O. YOST
		James O. Yost, Treasurer (Principal Financial Officer and Accounting Officer)

Date: April 16, 2020

*	Print name and title of each signing officer under his or her signature.

MFS Series Trust I - MFS Value Fund (MEIAX) N-CSRSCertified semi-annual shareholder report (management investment company)