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Summary Prospectus

May 1, 2025

SunAmerica Series Trust

SA Emerging Markets Equity Index Portfolio

(Class 1 and Class 3 Shares)

SunAmerica Series Trust’s Statutory Prospectus and Statement of Additional Information, each dated May 1, 2025, as amended and supplemented from time to time, and the most recent shareholder reports are incorporated into and made part of this Summary Prospectus by reference. The Portfolio is offered only to the separate accounts of certain affiliated and unaffiliated life insurance companies and to other mutual funds. This Summary Prospectus is not intended for use by other investors.

Before you invest, you may want to review SunAmerica Series Trust’s Statutory Prospectus, which contains more information about the Portfolio and its risks. You can find the Statutory Prospectus and the above-incorporated information online at https://www.corebridgefinancial.com/getprospectus. You can also get this information at no cost by calling (800) 445-7862 or by sending an e-mail request to fundprospectus@corebridgefinancial.com.

The Securities and Exchange Commission has not approved or disapproved these securities, nor has it determined that this Summary Prospectus is accurate or complete. It is a criminal offense to state otherwise.

Investment Goal

The Portfolio’s investment goal is investment results that correspond with the performance of the MSCI Emerging Markets Index.

Fees and Expenses of the Portfolio

This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Portfolio. The table and the example below do not reflect the separate account fees charged in the variable annuity or variable life insurance policy (“Variable Contracts”) in which the Portfolio is offered. If separate account fees were shown, the Portfolio’s annual operating expenses would be higher. Please see your Variable Contract prospectus for more details on the separate account fees.

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

	Class 1	Class 3
Management Fees	0.45%	0.45%
Service (12b-1) Fees	None	0.25%
Other Expenses	0.38%	0.38%
Acquired Fund Fees and Expenses1	0.02%	0.02%
Total Annual Portfolio Operating Expenses Before Fee Waivers and/ or Expense Reimbursements1	0.85%	1.10%
Fee Waivers and/or Expense Reimbursements2	0.25%	0.25%
Total Annual Portfolio Operating Expenses After Fee Waivers and/or Expense Reimbursements2	0.60%	0.85%

The Total Annual Portfolio Operating Expenses Before Fee Waivers and/or Expense Reimbursements do not correlate to the ratio of expenses to average net assets provided in the Financial Highlights table which reflects operating expenses of the Portfolio and do not include Acquired Fund Fees and Expenses.

Pursuant to an Expense Limitation Agreement, SunAmerica Asset Management, LLC (“SunAmerica”) has contractually agreed to waive its fees and/or reimburse expenses to the extent that the Total Annual Portfolio Operating Expenses of Class 1 and Class 3 shares exceed 0.58% and 0.83%, respectively, of the Portfolio’s average daily net assets. For purposes of the Expense Limitation Agreement, “Total Annual Portfolio Operating Expenses” shall not include extraordinary expenses (i.e., expenses that are unusual in nature and infrequent in occurrence, such as litigation), or acquired fund fees and expenses, brokerage commissions and other transactional expenses relating to the purchase and sale of portfolio securities, interest, taxes and governmental fees, and other expenses not incurred in the ordinary course of business of SunAmerica Series Trust (the “Trust”) on behalf of the Portfolio. Any waivers and/or reimbursements made by SunAmerica with respect to the Portfolio are subject to recoupment from the Portfolio within two years after the occurrence of the waivers and/or reimbursements, provided that the recoupment does not cause the expense ratio of the share class to exceed the lesser of (a) the expense limitation in effect at the time the waivers and/or reimbursements occurred, or (b) the current expense limitation of that share class. This agreement may be modified or discontinued prior to April 30, 2026, only with the approval of the Board of Trustees of the Trust, including a majority of the trustees who are not “interested persons” of the Trust as defined in the Investment Company Act of 1940, as amended.

Expense Example

This Example is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Portfolio for the time periods indicated and then redeem or hold all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Portfolio’s operating expenses remain the same (except that the Example incorporates any applicable fee waiver and/or

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expense limitation arrangements for only the first year). The Example does not reflect charges imposed by the Variable Contract. If the Variable Contract fees were reflected, the expenses would be higher. See the Variable Contract prospectus for information on such charges. Although your actual costs may be higher or lower, based on these assumptions and the net expenses shown in the fee table, your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class 1	$61	$246	$447	$1,026
Class 3	87	325	582	1,318

Portfolio Turnover

The Portfolio 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. These costs, which are not reflected in annual portfolio operating expenses or in the Example, affect the Portfolio’s performance.

During the most recent fiscal year, the Portfolio’s portfolio turnover rate was 11% of the average value of its portfolio.

Principal Investment Strategies of the Portfolio

The Portfolio seeks to provide investment results that correspond with the performance of the MSCI Emerging Markets Index (the “Index”). The Index includes a number of regions, market segments/sizes and covers approximately 85% of the free float-adjusted market capitalization in each of the countries represented in the Index.

The subadviser seeks to achieve the Portfolio’s objective by investing in a sampling of stocks included in the Index by utilizing a statistical technique known as “optimization.” The goal of optimization is to select stocks which ensure that characteristics such as industry weightings, average market capitalizations and fundamental characteristics (e.g., price-to-book, price-to-earnings, debt-to-asset ratios and dividend yields) closely approximate those of the Index. The subadviser may also invest the Portfolio’s assets in investments with economic characteristics that are comparable to the economic characteristics of securities included in the Index, including derivatives, such as contracts for difference. Stocks not in the Index may be held before or after changes in the composition of the Index or if they have characteristics similar to stocks in the Index. Under normal circumstances, all of the Portfolio’s investments will be selected through the optimization process, and at least 80% of its net assets will be invested in securities included in the Index or in

investments that the subadviser determines have economic characteristics that are comparable to the economic characteristics of securities included in the Index. The Portfolio may invest in ETFs, including to gain exposure to certain local markets that may be closed, or that are expensive or difficult to trade in local shares. The Portfolio will not concentrate, except to approximately the same extent as the Index may concentrate, in the securities of any industry. It is not anticipated, however, that the Portfolio will, under normal circumstances, be concentrated in the securities of any industry.

Because the Portfolio will generally not hold all of the stocks included in the Index, and because the Portfolio has expenses and the Index does not, the Portfolio will not duplicate the Index’s performance precisely. However, the subadviser believes there should be a close correlation between the Portfolio’s performance and that of the Index in both rising and falling markets.

Principal Risks of Investing in the Portfolio

As with any mutual fund, there can be no assurance that the Portfolio’s investment goal will be met or that the net return on an investment in the Portfolio will exceed what could have been obtained through other investment or savings vehicles. Shares of the Portfolio are not bank deposits and are not guaranteed or insured by any bank, government entity or the Federal Deposit Insurance Corporation. If the value of the assets of the Portfolio goes down, you could lose money.

The following is a summary of the principal risks of investing in the Portfolio.

Equity Securities Risk. The Portfolio invests principally in equity securities and is therefore subject to the risk that stock prices will fall and may underperform other asset classes. Individual stock prices fluctuate from day-to-day and may decline significantly.

Foreign Investment Risk. The Portfolio’s investments in the securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which the Portfolio invests may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of the Portfolio’s investments may decline because of factors affecting the particular issuer as well as foreign markets and issuers generally, such as unfavorable government actions, and political or financial instability and other conditions or events (including, for example, military confrontations, war, terrorism, sanctions, disease/virus, outbreaks and epidemics). Lack of relevant data and reliable public

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information may also affect the value of these securities. The risks of foreign investments are heightened when investing in issuers in emerging market countries.

Foreign Currency Risk. The value of the Portfolio’s foreign investments may fluctuate due to changes in currency exchange rates. A decline in the value of foreign currencies relative to the U.S. dollar generally can be expected to depress the value of the Portfolio’s non-U.S. dollar-denominated securities.

Emerging Markets Risk. Risks associated with investments in emerging markets may include: delays in settling portfolio securities transactions; currency and capital controls; greater sensitivity to interest rate changes; pervasive corruption and crime; exchange rate volatility; inflation, deflation or currency devaluation; violent military or political conflicts; confiscations and other government restrictions by the United States or other governments; and government instability. As a result, investments in emerging market securities tend to be more volatile than investments in developed countries.

Country Focus Risk. To the extent the Portfolio invests a significant portion of its assets in one or only a few countries at a time, the Portfolio will face a greater risk of loss due to factors affecting that single country or those few countries than if the Portfolio always maintained wide diversity among countries in which it invests.

Derivatives Risk. A derivative is any financial instrument whose value is based on, and determined by, another security, index, rate or benchmark (i.e., stock options, futures, caps, floors, etc.). To the extent a derivative contract is used to hedge another position in the Portfolio, the Portfolio will be exposed to the risks associated with hedging described below. To the extent an option, futures contract, swap, or other derivative is used to enhance return, rather than as a hedge, the Portfolio will be directly exposed to the risks of the contract. Unfavorable changes in the value of the underlying security, index, rate or benchmark may cause sudden losses. Gains or losses from the Portfolio’s use of derivatives may be substantially greater than the amount of the Portfolio’s investment. Certain derivatives have the potential for undefined loss. Derivatives are also associated with various other risks, including market risk, leverage risk, hedging risk, counterparty risk, valuation risk, regulatory risk, illiquidity risk and interest rate fluctuations risk. The primary risks associated with the Portfolio’s use of derivatives are market risk, counterparty risk and hedging risk.

ETF Risk. Most ETFs are investment companies whose shares are purchased and sold on a securities exchange. An investment in an ETF generally presents the same primary risks as an investment in a conventional fund (i.e.,

one that is not exchange-traded) that has the same investment objectives, strategies and policies. However, ETFs are subject to the following risks that do not apply to conventional mutual funds: (i) the market price of an ETF’s shares may trade at a premium or a discount to its net asset value; (ii) an active trading market for an ETF’s shares may not develop or be maintained; and (iii) there is no assurance that the requirements of the exchange necessary to maintain the listing of an ETF will continue to be met or remain unchanged. In addition, a passively-managed ETF may fail to accurately track the market segment or index that underlies its investment objective. To the extent that the Portfolio invests in an ETF, the Portfolio will indirectly bear its proportionate share of the management and other expenses that are charged by the ETF in addition to the expenses paid by the Portfolio.

Failure to Match Index Performance Risk. The ability of the Portfolio to match the performance of the Index may be affected by, among other things, changes in securities markets, the manner in which performance of the Index is calculated, changes in the composition of the Index, the amount and timing of cash flows into and out of the Portfolio, commissions, portfolio expenses, and any differences in the pricing of securities by the Portfolio and the Index. When the Portfolio employs an “optimization” strategy, the Portfolio is subject to an increased risk of tracking error, in that the securities selected in the aggregate for the Portfolio may perform differently than the underlying index.

Management Risk. The Portfolio is subject to management risk. The Portfolio’s portfolio managers apply investment techniques and risk analyses in making investment decisions, but there can be no guarantee that these decisions or the individual securities selected by the portfolio managers will produce the desired results.

“Passively Managed” Strategy Risk. The Portfolio will not deviate from its strategy, except to the extent necessary to comply with federal tax laws. If the Portfolio’s strategy is unsuccessful, the Portfolio will not meet its investment goal. Because the Portfolio will not use certain techniques available to other mutual funds to reduce stock market exposure, the Portfolio may be more susceptible to general market declines than other funds.

Issuer Risk. The value of a security may decline for a number of reasons directly related to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services.

Market Risk. The Portfolio’s share price or the market as a whole can decline for many reasons or be adversely affected by a number of factors, including, without limitation: weakness in the broad market, a particular

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industry, or specific holdings; adverse political, regulatory or economic developments in the United States or abroad; changes in investor psychology; heavy institutional selling; military confrontations, war, terrorism and other armed conflicts, disease/virus outbreaks and epidemics; recessions; taxation and international tax treaties; currency, interest rate and price fluctuations; and other conditions or events.

Affiliated Fund Rebalancing Risk. The Portfolio may be an investment option for other mutual funds for which SunAmerica serves as investment adviser that are managed as “funds of funds.” From time to time, the Portfolio may experience relatively large redemptions or investments due to the rebalancing of a fund of funds. In the event of such redemptions or investments, the Portfolio could be required to sell securities or to invest cash at a time when it is not advantageous to do so.

Performance Information

The following bar chart illustrates the risks of investing in the Portfolio by showing changes in the Portfolio’s performance from calendar year to calendar year and the table compares the Portfolio’s average annual returns to those of the MSCI ACWI ex-US Index (net) (a broad-based securities market index) and the MSCI Emerging Markets Index (net), which is relevant to the Portfolio because it has characteristics similar to the Portfolio’s investment strategies. Fees and expenses incurred at the contract level are not reflected in the bar chart or table. If these amounts were reflected, returns would be less than those shown. Of course, past performance is not necessarily an indication of how the Portfolio will perform in the future.

BlackRock Investment Management, LLC assumed subadvisory duties of the Portfolio on April 30, 2025. Prior to April 30, 2025, SunAmerica managed the Portfolio.

(Class 1 Shares)

During the period shown in the bar chart:

Highest Quarterly Return:	December 31, 2020	19.18%
Lowest Quarterly Return:	March 31, 2020	-24.35%
Year to Date Most Recent Quarter:	March 31, 2025	3.44%

Average Annual Total Returns (For the periods ended December 31, 2024)

	1 Year	5 Years	Since Inception	Inception Date
Class 1 Shares	5.82%	0.80%	0.92%	5/1/2018
Class 3 Shares	5.56%	0.55%	0.67%	5/1/2018
MSCI ACWI ex-U.S. Index (net)	5.53%	4.10%	3.65%
MSCI Emerging Markets Index (net)	7.50%	1.70%	1.30%

Investment Adviser

The Portfolio’s investment adviser is SunAmerica.

The Portfolio is subadvised by BlackRock Investment Management, LLC.

Portfolio Managers

Name and Title	Portfolio Manager of the Portfolio Since
Paul Whitehead Managing Director	2025
Jennifer Hsui, CFA Managing Director	2025
Peter Sietsema, CFA Director	2025
Matt Waldron, CFA Managing Director	2025
Steven White Director	2025

Purchases and Sales of Portfolio Shares

Shares of the Portfolios may only be purchased or redeemed through Variable Contracts offered by the separate accounts of participating life insurance companies and by other portfolios of the Trust and Seasons Series Trust. Shares of a Portfolio may be purchased and redeemed each day the New York Stock Exchange is open, at the Portfolio’s net asset value determined after receipt of a request in good order.

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The Portfolios do not have any initial or subsequent investment minimums. However, your insurance company may impose investment or account minimums. Please consult the prospectus (or other offering document) for your Variable Contract which may contain additional information about purchases and redemptions of Portfolio shares.

Tax Information

The Portfolios will not be subject to U.S. federal income tax so long as they qualify as regulated investment companies and distribute their income and gains each year to their shareholders. However, contractholders may be subject to U.S. federal income tax (and a U.S. federal Medicare tax of 3.8% that applies to net investment income, including taxable annuity payments, if applicable) upon withdrawal from a Variable Contract. Contractholders should consult the prospectus (or other offering document) for the Variable Contract for additional information regarding taxation.

Payments to Broker-Dealers and
Other Financial Intermediaries

The Portfolios are not sold directly to the general public but instead are offered as an underlying investment option for Variable Contracts and to other portfolios of the Trust and Seasons Series Trust. A Portfolio and its related companies may make payments to the sponsoring insurance company (or its affiliates) for distribution and/or other services. These payments may create a conflict of interest as they may be a factor that the insurance company considers in including a Portfolio as an underlying investment option in the Variable Contract. The prospectus (or other offering document) for your Variable Contract may contain additional information about these payments.

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