MFS Series Trust X

09/26/2024 | Press release | Distributed by Public on 09/26/2024 07:29

Summary Prospectus by Investment Company - Form 497K

SUMMARY PROSPECTUS

September 27, 2024

MFS® International Intrinsic Value Fund

Before you invest, you may want to review the fund's prospectus, which contains more information about the fund and its risks. You can find the fund's prospectus and other information about the fund, including the fund's reports to shareholders and statement of additional information, online at funds.mfs.com. You can also get this information at no cost by calling 1-800-225-2606 or by sending an e-mail request to [email protected]. The fund's prospectus and statement of additional information, both dated September 27, 2024, as may be amended or supplemented from time to time, are incorporated by reference into this summary prospectus.

CLASS

TICKER SYMBOL

Class A

MGIAX

Class B

MGIBX

Class C

MGICX

Class I

MINIX

Class R1

MINRX

Class R2

MINFX

Class R3

MINGX

Class R4

MINHX

Class R6

MINJX

Summary of Key Information

Investment Objective

The fund's investment objective is to seek capital appreciation.

Fees and Expenses

This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below.

You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in "Sales Charges and Waivers and Reductions" on page 11 and "Appendix A - Waivers and Reductions of Sales Charges" on page A-1 of the fund's prospectus.

Shareholder Fees (fees paid directly from your investment):

Share Class

A

B

C

I

R1

R2

R3

R4

R6

Maximum Sales Charge (Load)
Imposed on Purchases (as a percentage of offering price)

5.75%

None

None

None

None

None

None

None

None

Maximum Deferred Sales Charge (Load)
(as a percentage of original purchase price or redemption proceeds, whichever is less)

1.00%#

4.00%

1.00%

None

None

None

None

None

None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment):

Share Class

A

B

C

I

R1

R2

R3

R4

R6

Management Fee

0.65%

0.65%

0.65%

0.65%

0.65%

0.65%

0.65%

0.65%

0.65%

Distribution and/or Service (12b-1) Fees

0.25%

1.00%

1.00%

None

1.00%

0.50%

0.25%

None

None

Other Expenses1

0.16%

0.16%

0.16%

0.16%

0.16%

0.16%

0.16%

0.16%

0.05%

Total Annual Fund Operating Expenses

1.06%

1.81%

1.81%

0.81%

1.81%

1.31%

1.06%

0.81%

0.70%

Fee Reductions and/or Expense Reimbursements2

(0.01)%

(0.01)%

(0.01)%

(0.01)%

(0.01)%

(0.01)%

(0.01)%

(0.01)%

(0.01)%

Total Annual Fund Operating Expenses After Fee Reductions and/or Expense Reimbursements

1.05%

1.80%

1.80%

0.80%

1.80%

1.30%

1.05%

0.80%

0.69%

#This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase.

1"Other Expenses" include approximately 0.03% of foreign tax reclaim recovery expenses (including contingency fees and closing agreement expenses to be paid to third party service providers) incurred in connection with the fund's recovery of foreign taxes previously withheld in certain foreign countries. The amount of the fund's foreign tax reclaim recoveries is greater than the tax reclaim recovery expenses referenced above.

2Massachusetts Financial Services Company (MFS) has agreed in writing to waive at least 0.01% of the fund's management fee as part of an agreement pursuant to which MFS has agreed 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. The agreement to waive at least 0.01% of the management fee will continue until modified by the fund's Board of Trustees, but such agreement will continue until at least September 30, 2025.

FGI-SUM-092724Page 1 of 4

MFS International Intrinsic Value Fund

Example

This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds.

The example assumes that: you invest $10,000 in the fund for the time periods indicated and you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund's operating expenses remain the same.

Although your actual costs will likely be higher or lower, under these assumptions your costs would be:

1 YEAR

3 YEARS

5 YEARS

10 YEARS

Class A Shares

$676

$892

$1,125

$1,794

Class B Shares assuming1

redemption at end of period

$583

$868

$1,179

$1,929

no redemption at end of period

$183

$568

$979

$1,929

Class C Shares assuming1

redemption at end of period

$283

$568

$979

$1,929

no redemption at end of period

$183

$568

$979

$1,929

Class I Shares

$82

$258

$449

$1,001

Class R1 Shares

$183

$568

$979

$2,126

Class R2 Shares

$132

$414

$717

$1,578

Class R3 Shares

$107

$336

$584

$1,293

Class R4 Shares

$82

$258

$449

$1,001

Class R6 Shares

$70

$223

$389

$870

1Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These transaction costs, which are not reflected in "Annual Fund Operating Expenses" or in the "Example," affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 12% of the average value of its portfolio.

Principal Investment Strategies

MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund's assets primarily in foreign equity securities, including emerging market equity securities. Equity securities include common stocks, depositary receipts, and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.

MFS focuses on investing the fund's assets in the stocks of companies that it believes are undervalued compared to their intrinsic value. MFS evaluates the intrinsic value of a company by considering the full context of how the company's cash flows are generated. MFS focuses on companies it believes have intrinsic value greater than the perceived value by the marketplace and seeks to invest in companies that exhibit characteristics such as cash flow in excess of capital expenditures, conservative balance sheets, sustainable competitive advantages, high returns on capital, and/or the ability to weather economic downturns. These companies may have stock prices that are higher relative to their earnings, dividends, assets, or other financial measures than companies generally considered value companies under a traditional value investment strategy.

MFS may invest the fund's assets in securities of companies of any size.

MFS normally invests the fund's assets across different industries, sectors, countries, and regions, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry, sector, country, or region.

While MFS may use derivatives for any investment purpose, to the extent MFS uses derivatives, MFS expects to use derivatives primarily to increase or decrease currency exposure. Derivatives include futures, forward contracts, options, and swaps.

MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative screening tools that systematically evaluate issuers may also be considered.

Principal Risks

As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

The principal risks of investing in the fund are:

Investment Selection Risk: MFS' investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. In addition, to the extent MFS considers quantitative tools in managing the fund, such tools may not produce the intended results.

Equity Market Risk/Company Risk:Equity markets are volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general. Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market. The value of an investment held by the fund may decline due to factors directly related to the issuer.

Intrinsic Value Strategy Risk: The stocks of companies that MFS believes are undervalued compared to their intrinsic value can continue to be undervalued for long periods of time, may not realize their expected value, and can be volatile.

Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to emerging markets or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market.

Emerging Markets Risk: Investments tied economically to emerging markets, especially frontier markets, can involve additional and greater risks than the risks associated with investments in developed markets. Emerging markets can have less developed markets, greater custody and operational risk, less developed legal, regulatory, and accounting systems, greater

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MFS International Intrinsic Value Fund

government involvement in the economy, greater risk of new or inconsistent government treatment of or restrictions on issuers and instruments, and greater political, social, geopolitical, and economic instability than developed markets.

Currency Risk: The value of foreign currencies relative to the U.S. dollar fluctuates in response to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions, and changes in currency exchange rates impact the financial condition of companies or other issuers and may change the value in U.S. dollars of investments denominated in foreign currencies.

Focus Risk: Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed.

Derivatives Risk: Derivatives can be highly volatile and involve risks in addition to the risks of the underlying indicator(s) on which the derivative is based. Gains or losses from derivatives can be substantially greater than the derivatives' original cost. Derivatives can involve leverage.

Leveraging Risk: Leverage involves investment exposure in an amount exceeding the initial investment. Leverage can cause increased volatility by magnifying gains or losses.

Counterparty and Third Party Risk: Transactions involving a counterparty or third party other than the issuer of the instrument are subject to the credit risk of the counterparty or third party, and to the counterparty's or third party's ability or willingness to perform in accordance with the terms of the transaction.

Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs.

Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares. These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would.

Performance Information

The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund's performance over time and how the fund's performance over time compares with that of (i) a broad measure of market performance and (ii) one or more other measures of performance for markets in which the fund invests.

The fund's past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606.

Class A Bar Chart. The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund's shares. If these sales charges were included, they would reduce the returns shown.

The total return for the six-month period ended June 30, 2024, was 6.80%. During the period(s) shown in the bar chart, the highest quarterly return was 16.58% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (15.15)% (for the calendar quarter ended June 30, 2022).

Performance Table.

Average Annual Total Returns

(For the Periods Ended December 31, 2023)

Share Class

1 YEAR

5 YEARS

10 YEARS

Returns Before Taxes

B Shares

12.75%

7.37%

6.20%

C Shares

15.72%

7.66%

6.21%

I Shares

17.92%

8.75%

7.11%

R1 Shares

16.72%

7.66%

6.04%

R2 Shares

17.33%

8.21%

6.58%

R3 Shares

17.60%

8.47%

6.84%

R4 Shares

17.90%

8.75%

7.11%

R6 Shares

18.05%

8.86%

7.22%

A Shares

10.87%

7.20%

6.21%

Returns After Taxes on Distributions

A Shares

8.21%

5.31%

4.96%

Returns After Taxes on Distributions and Sale of Fund Shares

A Shares

8.56%

5.71%

4.96%

Index Comparisons (Reflects no deduction for fees, expenses, or taxes)

MSCI EAFE (Europe, Australasia, Far East) Index (net div)

18.24%

8.16%

4.28%

MSCI EAFE (Europe, Australasia, Far East) Value Index (net div)

18.95%

7.08%

3.16%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (IRAs). The after-tax returns are shown for only one of the fund's classes of shares, and after-tax returns for the fund's other classes of shares will vary from

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MFS International Intrinsic Value Fund

the returns shown.

Investment Adviser

MFS serves as the investment adviser for the fund.

Portfolio Manager(s)

Portfolio Manager

Since

Title

Philip Evans

2020

Investment Officer of MFS

Benjamin Stone

2008

Investment Officer of MFS

Purchase and Sale of Fund Shares

You may purchase and redeem shares of the fund each day the New York Stock Exchange (the NYSE) is open for trading. You may purchase or redeem shares either by having your financial intermediary process your purchase or redemption, or through MFS Service Center, Inc. (MFSC) by overnight mail (MFSC, Suite 219341, 430 W 7th Street, Kansas City, MO 64105-1407), by mail ([Fund Name], P.O. Box 219341, Kansas City, MO 64121-9341), by telephone (1-800-225-2606), or via the Internet at mfs.com (MFS Access).

The fund's initial and subsequent investment minimums generally are as follows:

Class

Initial Minimum

Subsequent Minimum

Class A, Class B, Class C

None - automatic investment plans and certain asset-based fee programs

$25 - employer-sponsored retirement plans

$250 - Traditional and Roth IRAs

$1,000 - other accounts

$50 - by check and non-systematic written exchange request, and via MFSC telephone representatives

None - other purchases

Class I, Class R1, Class R2, Class R3, Class R4, Class R6

None

None

Effective at the close of business on May 29, 2015, the fund was closed to new investors subject to certain exceptions. Shareholders of the fund as of June 15, 2018, can continue to make additional purchases and reinvest distributions in the fund in any account open as of June 15, 2018. Shareholders of the fund as of June 15, 2018, may also: 1) exercise their one-time Reinstatement Privilege (described in Appendix A of this prospectus) to reinvest in shares of the fund within 90 days of a redemption of fund shares; and 2) transfer some or all of the shares in their account to another account and such account will be treated as having been open as of June 15, 2018.

In addition, as of June 15, 2018, shares of the fund may be purchased by the following investors:

·Retirement plans other than traditional IRAs, SIMPLE IRAs, Roth IRAs, SEP plans, and SARSEP plans if the fund was offered or selected as an investment option by such plan (or any predecessor plan or other plan sponsored by the same employer) as of October 16, 2017;

·Qualified tuition programs established under Section 529 of the Internal Revenue Code of 1986, as amended, if the fund was offered as an investment option by such program on May 29, 2015;

·Accounts maintained by a registered broker-dealer on its books for which investment decisions are determined by the registered broker-dealer's home office discretionary model portfolios that are controlled by a centralized group responsible for creating such model portfolios and that included the fund as of June 15, 2018 (approved and recommended fund lists are not included within this exception); and

·Investors approved by the fund, the fund's investment adviser, and the fund's distributor.

The fund reserves the right to modify or limit the above exceptions, or re-open the fund at any time without prior notice.

Financial intermediaries are responsible for enforcing these restrictions with respect to their investors. MFS' ability to monitor financial intermediaries' enforcement of these restrictions is limited by operational systems and the cooperation of financial intermediaries. In addition, with respect to omnibus accounts, MFS' ability to monitor is also limited by a lack of information with respect to the underlying shareholder accounts.

Purchases of Class B shares are closed to new and existing investors except through reinvestment of dividends and capital gain distributions. Existing investors may continue to exchange their Class B shares for the same share class of another MFS fund.

Purchases of Class R1 and Class R2 shares are closed to new eligible investors. Existing eligible investors can make additional purchases and reinvest distributions in Class R1 and Class R2 shares in any account open. Existing eligible investors may also exchange their Class R1 and Class R2 shares for the same share class of another MFS fund, open new Class R1 and Class R2 share accounts in other MFS funds, or transfer some or all of the shares in their account to another account and such account will be treated as an open account. Subject to the approval of the fund's Board of Trustees, the fund may in the future (i) close purchases of Class R1 and/or Class R2 shares to existing eligible investors; (ii) terminate and liquidate Class R1 and/or Class R2 shares; or (iii) convert Class R1 and/or Class R2 shares to another share class of the fund. Such actions may be undertaken without shareholder approval, but the fund expects to provide shareholders with at least 60 days' notice before taking any such action.

Taxes

If your shares are held in a taxable account, the fund's distributions will be taxed to you as ordinary income and/or capital gains. If your shares are held in a tax-advantaged account, you will generally be taxed only upon withdrawals from the account.

Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the fund through a broker/dealer or other financial intermediary (such as a bank), the fund, MFS, and/or MFS' affiliates may pay the financial intermediary for the sale of shares of the fund and/or the servicing of shareholder accounts. These payments may create a conflict of interest by influencing your broker/dealer or other financial intermediary and your salesperson to recommend the fund over another investment. Ask your financial intermediary or visit your financial intermediary's website for more information.

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