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Summary Prospectus

May 1, 2025

SunAmerica Series Trust

SA Index Allocation 80/20 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 goals are growth of capital and, secondarily, current income.

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. As an investor in the Portfolio, you pay the expenses of the Portfolio and indirectly pay a proportionate share of the expenses of the Underlying Portfolios (as defined herein) in which the Portfolio invests.

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	0.10%	0.10%
Service (12b-1) Fees	None	0.25%
Other Expenses	0.02%	0.02%
Acquired Fund Fees and Expenses1	0.32%	0.32%
Total Annual Portfolio Operating Expenses1	0.44%	0.69%

The Total Annual Portfolio Operating Expenses 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.

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 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	$45	$141	$246	$555
Class 3	70	221	384	859

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 5% of the average value of its portfolio.

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SA Index Allocation 80/20 Portfolio

Principal Investment Strategies of the Portfolio

The Portfolio is structured as a “fund-of-funds,” which means that it pursues its investment goal by investing its assets in a combination of other mutual funds (the “Underlying Portfolios”). The Underlying Portfolios will primarily include other funds in the Trust but may also include other funds advised by the Adviser. Under normal circumstances, the Portfolio will seek to allocate 80% of its assets (with a range of 70% to 90%) to Underlying Portfolios investing primarily in equity securities (“Underlying Equity Portfolios”) and 20% of its assets (with a range of 10% to 30%) to Underlying Portfolios investing primarily in fixed income securities (“Underlying Fixed Income Portfolios”). The Underlying Equity Portfolios include, among others, funds that invest in domestic and international equity securities of small, medium and/or large capitalization companies and the Underlying Fixed Income Portfolios include, among others, funds that invest in domestic government and corporate bonds.

The Underlying Portfolios will generally be limited to index funds, which are passively managed to track the performance of designated indices, although the Portfolio may also from time to time invest in Underlying Portfolios that are not index funds, including for cash management purposes. The Portfolio may invest a significant portion of its assets in any single Underlying Portfolio. The following chart sets forth the Portfolio’s target allocations set by SunAmerica Asset Management, LLC (“SunAmerica”) on January 31, 2025 to the Underlying Equity Portfolios and Underlying Fixed Income Portfolios. The Portfolio’s actual allocations may vary from these projections and will fluctuate from time to time due to, among other things, market conditions and changes made by the Adviser to the target allocations.

Underlying Portfolio	% of Total Portfolio
Equity	80.00%
SA Large Cap Index Portfolio	50.40%
SA Mid Cap Index Portfolio	10.10%
SA Small Cap Index Portfolio	5.00%
SA International Index Portfolio	14.50%
Fixed Income	20.00%
SA Fixed Income Intermediate Index Portfolio	10.00%
SA Fixed Income Index Portfolio	10.00%

The Underlying Portfolio selection is made based on the Portfolio’s particular asset allocation strategy. The Adviser may adjust the Portfolio’s allocation to the Underlying Portfolios from time to time as it deems necessary,

including based on market conditions or other factors. The Adviser intends to rebalance the Portfolio on an ongoing basis using cash flows; however, it reserves the right to rebalance the Portfolio through exchanges at any time.

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.

Asset Allocation Risk. The Portfolio’s risks will directly correspond to the risks of the Underlying Portfolios in which it invests. The Portfolio is subject to the risk that the selection of the Underlying Portfolios and the allocation and reallocation of the Portfolio’s assets among the various asset classes and market sectors may not produce the desired result.

Equity Securities Risk. The Portfolio invests principally in Underlying Portfolios that invest 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.

Large-Cap Companies Risk. The Portfolio invests in Underlying Portfolios that invest substantially in large-cap companies. Large-cap companies tend to be less volatile than companies with smaller market capitalizations. In exchange for this potentially lower risk, the Portfolio’s value may not rise as much as the value of portfolios that emphasize smaller companies. Larger, more established companies may be unable to respond quickly to new competitive challenges, such as changes in technology and consumer tastes. Larger companies also may not be able to attain the high growth rate of successful smaller companies, particularly during extended periods of economic expansion.

Small- and Medium-Sized Companies Risk. The Portfolio invests in Underlying Portfolios that may invest in securities of small- and medium-capitalization companies. Securities of small- and medium-sized companies are usually more volatile and entail greater risks than securities of large companies.

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SA Index Allocation 80/20 Portfolio

Foreign Investment Risk. The Portfolio’s investments in Underlying Portfolios that invest in the securities of foreign issuers or issuers with significant exposure to foreign markets involve additional risk. Foreign countries in which an Underlying Portfolio may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of the Underlying 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 information may also affect the value of these securities.

Foreign Currency Risk. The value of an Underlying 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 an Underlying Portfolio’s non-U.S. dollar-denominated securities.

Bonds Risk. The Portfolio invests in Underlying Portfolios that invest principally in bonds, which may cause the value of your investment in the Portfolio to go up or down in response to changes in interest rates or defaults (or even the potential for future defaults) by bond issuers. Fixed income securities may be subject to volatility due to changes in interest rates.

Credit Risk. Credit risk applies to most fixed income securities, but is generally not a factor for obligations backed by the “full faith and credit” of the U.S. Government. An Underlying Portfolio could lose money if the issuer of a fixed income security is unable or perceived to be unable to pay interest or to repay principal when it becomes due.

An issuer with a lower credit rating will be more likely than a higher rated issuer to default or otherwise become unable to honor its financial obligations. Issuers with low credit ratings typically issue junk bonds. In addition to the risk of default, junk bonds may be more volatile, less liquid, more difficult to value and more susceptible to adverse economic conditions or investor perceptions than other bonds.

Interest Rate Risk. The Portfolio invests in Underlying Portfolios that invest substantially in fixed income securities. Fixed income securities may be subject to volatility due to changes in interest rates. Duration is a measure of interest rate risk that indicates how price-sensitive a bond is to changes in interest rates. Longer-term and lower coupon bonds tend to be more sensitive to

changes in interest rates. The Federal Reserve has recently begun to raise the federal funds rate to address rising inflation. As interest rates rise from historically low levels, the Portfolio may face heightened interest rate risk. For example, a bond with a duration of three years will decrease in value by approximately 3% if interest rates increase by 1%. Any future changes in monetary policy made by central banks and/or their governments are likely to affect the level of interest rates.

Management Risk. The Portfolio is subject to management risk because it is an actively managed investment portfolio. 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 individual securities selected by the portfolio managers will produce the desired results.

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 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. In addition, an Underlying Portfolio’s adviser’s or subadviser’s assessment of companies held in the Underlying Portfolio may prove incorrect, resulting in losses or poor performance even in a rising market.

Indexing Risk. The Underlying Portfolios in which the Portfolio invests are managed to track the performance of an index. An Underlying Portfolio will not sell securities in its portfolio or buy different securities over the course of a year other than in conjunction with changes in its target index, even if there are adverse developments concerning a particular security, company or industry. As a result, the Portfolio may suffer losses that might not be experienced with an investment in an actively-managed mutual fund.

Fund-of-Funds Risk. The costs of investing in the Portfolio, as a fund-of-funds, may be higher than the costs of investing in a mutual fund that invests most or all of its assets directly in individual securities. An Underlying Portfolio may change its investment objective or policies without the Portfolio’s approval, which could force the Portfolio to withdraw its investment from such Underlying

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SA Index Allocation 80/20 Portfolio

Portfolio at a time that is unfavorable to the Portfolio. In addition, one Underlying Portfolio may buy the same securities that another Underlying Portfolio sells. Therefore, the Portfolio would indirectly bear the costs of these trades without accomplishing any investment purpose.

Underlying Portfolios Risk. The risks of the Portfolio owning the Underlying Portfolios generally reflect the risks of owning the underlying securities held by the Underlying Portfolios. Disruptions in the markets for the securities held by the Underlying Portfolios could result in losses on the Portfolio’s investment in such securities. The Underlying Portfolios also have fees that increase their costs versus owning the underlying securities directly.

Affiliated Portfolio Risk. In managing the Portfolio, SunAmerica will have the authority to select and substitute the Underlying Portfolios. SunAmerica may be subject to potential conflicts of interest in allocating the Portfolio’s assets among the various Underlying Portfolios because the fees payable to it by some of the Underlying Portfolios are higher than the fees payable by other Underlying Portfolios and because SunAmerica also is responsible for managing and administering the Underlying Portfolios.

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 S&P 500® Index (a broad-based securities market index) and a blended index. The blended index consists of 50% S&P 500® Index, 10% S&P MidCap 400® Index, 5% Russell 2000® Index, 15% MSCI EAFE Index (net), 10% Bloomberg U.S. Government/Credit Index and 10% Bloomberg Intermediate U.S. Government/Credit Index (the “Blended Index”). The Blended Index 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.

(Class 3 Shares)

During the period shown in the bar chart:

Highest Quarterly Return:	June 30, 2020	16.31%
Lowest Quarterly Return:	March 31, 2020	-17.22%
Year to Date Most Recent Quarter:	March 31, 2025	-2.04%

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

	1 Year	5 Years	Since Inception	Inception Date
Class 1 Shares	15.18%	9.33%	9.66%	2/6/2017
Class 3 Shares	14.86%	9.04%	9.38%	2/6/2017
S&P 500® Index (reflects no deduction for fees, expenses or taxes)	25.02%	14.53%	14.61%
Blended Index	15.27%	9.65%	10.08%

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SA Index Allocation 80/20 Portfolio

Investment Adviser

The Portfolio’s investment adviser is SunAmerica.

Portfolio Managers

Name and Title	Portfolio Manager of the Portfolio Since
Andrew Sheridan Lead Portfolio Manager	2021
Manisha Singh, CFA Co-Portfolio Manager	2017
Robert Wu, CFA Co-Portfolio Manager	2021

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.

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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