Summary Prospectus by Investment Company (Form 497K)

Before you invest, you may want to review the Fund's prospectus and statement of additional information, which contain more information about the Fund and its risks. The current prospectus and statement of additional information, dated May 1, 2026, are incorporated by reference into this summary prospectus. You can find the Fund's prospectus, statement of additional information, reports to shareholders, and other information about the Fund online at https://americanbeaconfunds.com/fund-resources/. You can also get this information at no cost by calling 1-800-658-5811 or by sending an email request to [email protected].

Investment Objective

The Fund seeks long-term growth of capital.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy, hold, and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales discounts if you and your eligible family members invest, or agree to invest in the future, at least $50,000 in all classes of the American Beacon Funds on an aggregated basis. More information about these and other discounts is available from your financial professional and in "Choosing Your Share Class" on page  21 of the Prospectus and "Additional Purchase and Sale Information for A Class Shares" on page  33  of the Statement of Additional Information ("SAI"). With respect to purchases of shares through specific intermediaries, you may find additional information regarding sales charge discounts and waivers in Appendix A to the Fund's Prospectus entitled "Intermediary Sales Charge Discounts, Waivers and Other Information."

Shareholder Fees (fees paid directly from your investment)

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 then redeem 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 Fund's operating expenses remain the same, except that this Example reflects the fee waiver/expense reimbursement arrangement for each share class through April 30, 2027. C Class shares automatically convert to A Class shares 8 years after purchase, if the conversion is available through your financial intermediary. This Example reflects your costs as though C Class shares were held for the full 10-year period. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

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American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus1

Assuming no redemption of shares:

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 Fund shares are held in a taxable account. These 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 51% of the average value of its portfolio.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in equity securities of medium market capitalization companies that the Fund considers to have growth characteristics.

The Fund considers a company to be a medium market capitalization company if it has a market capitalization between $1 billion and the market capitalization of the largest company in the Russell  Midcap® Index, which was $128.84  billion as of February 28, 2026. The Russell  Midcap Index measures the performance of the approximately 800 smallest companies in the Russell 1000® Index, which measures the performance of the approximately 1,000 largest U.S. companies based on total market capitalization.

The Fund's sub-advisor, Stephens Investment Management Group, LLC ("SIMG"), principally invests in companies that it believes to have clear indicators of future earnings growth, or that demonstrate other potential for growth of capital. SIMG primarily employs fundamental research to identify companies with growth potential using year-over-year earnings per share growth rate or sales growth rate. If either such rate for a company is in the top 20% of such rates for companies in the Russell Midcap® Growth Index, then the Fund considers that company to have growth characteristics. The Russell Midcap Growth Index includes those Russell Midcap Index companies with relatively higher price-to-book ratios, earnings per share growth rates and sales growth rates.

The Fund's equity investments include  U.S. common stocks and U.S. dollar denominated foreign stocks traded on U.S. exchanges. In addition to medium market capitalization companies, the Fund may also invest in equity securities of small-capitalization and large-capitalization companies. SIMG will sell a security when appropriate and consistent with the Fund's investment objective and policies.

Although the Fund seeks investments across a number of sectors, from time to time, the Fund may have significant positions in particular sectors, including the Information Technology sector.   However, as the sector composition of the Fund's portfolio changes over time, the Fund's exposure to the Information Technology sector may be lower at a future date, and the Fund's exposure to other market sectors may be higher.

The Fund may also invest cash balances in other investment companies, including a government money market fund advised by the Manager, with respect to which the Manager receives a management fee. The Fund may seek to earn additional income by lending its securities to certain qualified broker-dealers and institutions.

Principal Risks

There is no assurance that the Fund will achieve its investment objective, and you could lose part or all of your investment in the Fund. The Fund is not designed for investors who need an assured level of current income and is intended to be a long-term investment. The Fund is not a complete investment program and may not be appropriate for all investors. Investors should carefully consider their own investment goals and risk tolerance before investing in the Fund. The principal risks of investing in the Fund listed below are presented in alphabetical order and not in order of importance or potential exposure. Among other matters, this presentation is intended to facilitate your ability to find particular risks and compare them with the risks of other funds. Each risk summarized below is considered a "principal risk" of investing in the Fund, regardless of the order in which it appears.  

Cybersecurity and Operational Risk
Operational risks arising from, among other problems, human errors, systems and technology disruptions or failures, or cybersecurity incidents may negatively impact the Fund, its service providers and third-party fund distribution platforms, including the ability of shareholders to transact in the Fund's shares, and result in financial losses. Cybersecurity incidents may allow an unauthorized party to gain access to Fund assets, shareholder data, or proprietary information, or cause the Fund or its service providers, as well as securities trading venues and their service providers, to suffer data corruption or lose operational functionality. Cybersecurity incidents can result from deliberate attacks or unintentional events. It is not possible for the Fund or its service providers to identify all of the operational risks that may affect the Fund or to develop processes and controls to completely eliminate or mitigate their occurrence or effects. The Fund cannot control the cybersecurity and operational plans and systems of its service providers, its counterparties or the issuers of securities in which the Fund invests. The issuers of the Fund's investments are likely to be dependent on computers for their operations and require ready access to their data and the internet to conduct their business. Thus, cybersecurity incidents could also affect issuers of the Fund's investments, leading to significant loss of value.

Equity Investments Risk
Equity securities represent ownership interests in companies and are subject to investment risk, issuer risk and market risk. In general, the values of stocks and other equity securities fluctuate, and sometimes widely fluctuate, in response to changes in a company's financial condition as well as general market, economic and political conditions and other factors. The Fund may experience a significant or complete loss on its investment in an equity security. In addition, stock prices may be particularly sensitive to rising interest rates, which increase borrowing costs and the costs of capital.  The Fund may invest in the following equity securities, which may expose the Fund to the following additional risks:

2American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus

Foreign Exposure Risk
Exposure to  non-U.S. issuers carries potential risks not associated with exposure to U.S. issuers. Such risks may include, but are not limited to: (1) political and financial instability, (2) less liquidity, (3) greater volatility, and (4) different government regulation The Fund's exposure to a foreign issuer may subject the Fund to regulatory, political, currency, security, economic and other risks associated with that country, including tariffs, trade disputes and sanctions. Global economic and financial markets have become increasingly interconnected and conditions (including recent volatility, terrorism, war and political instability) and events (including natural disasters) in one country, region or financial market may adversely impact issuers in a different country, region or financial market.

Growth Companies Risk
Growth companies are expected to increase their earnings at a certain rate. When these expectations are not met or decrease, the prices of these stocks may decline, sometimes sharply, even if earnings showed an absolute increase. The Fund's investments in growth companies may be more sensitive to company earnings and more volatile than the market in general primarily because their stock prices are based heavily on future expectations. If an assessment of the prospects for a company's growth is incorrect, then the price of the company's stock may fall or not approach the value placed on it. Growth company stocks may also lack the dividend yield that can cushion stock price declines in market downturns.

Investment Risk
An investment in the Fund is not a deposit with a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. When you sell your shares of the Fund, they could be worth less than what you paid for them. Therefore, you may lose money by investing in the Fund.

Issuer Risk
The value of, and/or the return generated by, a security may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's goods or services, as well as the historical and prospective earnings of the issuer and the value of its assets.

Large-Capitalization Companies Risk
The securities of large market capitalization companies may underperform other segments of the market because such companies may be less responsive to competitive challenges and opportunities and, at times, such companies may be out of favor with investors. Many larger-capitalization companies also may be unable to attain the high growth rates of successful smaller companies, especially during periods of economic expansion.

Market Risk
The Fund is subject to the risk that the securities markets will move down, sometimes rapidly and unpredictably, based on overall economic conditions and other factors, which may negatively affect the Fund's performance. The financial markets generally move in cycles, with periods of rising prices followed by periods of declining prices. The value of your investment may reflect these fluctuations. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Even when certain securities prices have generally increased over time, there have been periods of price decreases during those times, resulting in losses for investors, which are likely to occur again in the future.

Geopolitical and other events, including war, terrorism, trade disputes, pandemics, public health crises, natural disasters, and  cybersecurity incidents, have led, and in the future may continue to lead, to general instability in world economies and markets and reduced liquidity in securities, which may negatively affect the value of your investment.

Policies established by the  U.S. government and/or Federal Reserve and economic and political circumstances within the U.S. and abroad, such as inflation, changes in interest rates, recessions, changes in government leadership, a government's inability to agree on a budget, high public debt, the threat or occurrence of a federal government shutdown and threats or the occurrence of a failure to increase the federal government's debt limit, which could result in a default on the government's obligations, may negatively affect investor and consumer confidence and may negatively impact financial markets and the broader economy, perhaps suddenly and to a significant degree.

Markets and market participants are increasingly reliant upon public and proprietary data and systems. Data or technology malfunctions and inaccuracies may disrupt markets and lead to negative consequences for market participants like the Fund.  

Mid-Capitalization Companies Risk
Investing in the securities of mid-capitalization companies involves greater risk and the possibility of greater price volatility, which at times can be rapid and unpredictable, than investing in larger-capitalization and more established companies. Since mid-capitalization companies may have narrower commercial markets

American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus3

and more limited operating history, product lines, and managerial and financial resources than larger, more established companies, the securities of these companies may lack sufficient market liquidity, and they can be particularly sensitive to changes in overall economic conditions, interest rates, borrowing costs and earnings.

Other Investment Companies Risk
To the extent that the Fund invests in shares of other registered investment companies, the Fund will indirectly bear the fees and expenses charged by those investment companies in addition to the Fund's direct fees and expenses. To the extent the Fund invests in other investment companies that invest in equity securities, fixed-income securities and/or foreign securities, or that track an index, the Fund is subject to the risks associated with the underlying investments held by the investment company or the index fluctuations to which the investment company is subject. The Fund will be subject to the risks associated with investments in those companies, including but not limited to the following:

Redemption Risk
The Fund may experience periods of high levels of redemptions that could cause the Fund to sell assets at inopportune times or at a loss or depressed value. Heavy redemptions could hurt the Fund's performance. The sale of assets to meet redemption requests may create net capital gains, which could cause the Fund to have to distribute substantial capital gains. Redemption risk is greater to the extent that one or more investors or intermediaries control a large percentage of investments in the Fund. In addition, redemption risk is heightened during periods of declining or illiquid markets. During periods of heavy redemptions, the Fund may borrow funds through the interfund credit facility or from a bank line of credit, which may increase costs.

Sector Risk
When the Fund focuses its investments in certain sectors of the economy, its performance could fluctuate more widely than if the Fund were invested more evenly across sectors. Issuers in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly. Additionally, individual sectors may be more volatile, and may perform differently, than the broader market. As the Fund's portfolio changes over time, the Fund's exposure to a particular sector may become higher or lower.

Securities Lending Risk
To the extent the Fund lends its securities, it may be subject to the following risks: (i) the securities in which the Fund reinvests cash collateral may decrease in value, causing the Fund to incur a loss, or may not perform sufficiently to cover the Fund's payment to the borrower of a pre-negotiated fee or "rebate" for the use of that cash collateral in connection with the loan; (ii) non-cash collateral may decline in value, resulting in the Fund becoming under-secured; (iii) delays may occur in the recovery of loaned securities from borrowers, which could result in the Fund being unable to vote proxies or settle transactions or cause the Fund to incur increased costs; and (iv) if the borrower becomes subject to insolvency or similar proceedings, the Fund could incur delays in its ability to enforce its rights in its collateral.

Securities Selection Risk
Securities selected for the Fund may not perform to expectations. This could result in the Fund's underperformance compared to its performance index(es), or other funds with similar investment objectives or strategies.

Small-Capitalization Companies Risk
Investing in the securities of small-capitalization companies involves greater risk and the possibility of greater price volatility, which at times can be rapid and unpredictable, than investing in larger-capitalization and more established companies. Since small-capitalization companies may have narrower commercial markets, and more limited operating history, product lines, and managerial and financial resources than larger, more established companies, the securities of these companies may lack sufficient market liquidity and they can be particularly sensitive to changes in overall economic conditions, interest rates, borrowing costs and earnings.

Fund Performance

The bar chart and table below provide an indication of risk by showing changes in the Fund's performance over time. The bar chart shows how the Fund's performance has varied from year to year. The table shows how the Fund's average annual total returns compare to a broad-based securities market index, as well as an additional index with characteristics that are similar to those of the Fund, for the periods indicated.

The chart and the table show the performance of the Fund's Investor Class shares for all periods. In the table below, for the period prior to December 31, 2018, the performance of the Fund's R6 Class shares reflects the returns of the R5 Class shares of the Fund. The R6 Class shares would have had similar annual returns to the R5 Class shares because the shares of each class represent investments in the same portfolio securities. However, as reflected in the "Fees and Expenses of the Fund" section of this Fund Summary, the expenses of the R5 Class shares differ from those of the R6 Class shares, which would affect performance. To the extent that the Fund's R5 Class shares may have had lower expenses than the R6 Class shares prior to December 31, 2018, the performance of the R5 Class shares would likely have been higher than the performance the R6 Class shares would have realized during the same period. The performance of the R6 Class shares shown in the table has not been adjusted for differences in operating expenses between that share class and the R5 Class shares.

C Class shares automatically convert to A Class shares 8 years after purchase, if the conversion is available through your financial intermediary.  In the table below, the performance for C Class shares reflects the performance as though C Class shares were held for the full 10 year period. You may obtain updated performance information on the Fund's website at  www.americanbeaconfunds.com. Past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

4American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus

Average annual total returns for periods ended December 31, 2025

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 income taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. The return after taxes on distributions and sale of Fund shares may exceed the return before taxes due to an assumed tax benefit from any losses on a sale of Fund shares at the end of the measurement period. If you are a tax-exempt entity or hold your Fund shares through a tax-deferred arrangement, such as an individual retirement account ("IRA") or a 401(k) plan, the after-tax returns do not apply to your situation. After-tax returns are shown only for Investor Class shares of the Fund; after-tax returns for other share classes will vary.

Management

The Manager
The Fund has retained American Beacon Advisors, Inc. to serve as its Manager.

Sub-Advisor

The Fund's investment sub-advisor is Stephens Investment Management Group, LLC.

Portfolio Managers

American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus5

Purchase and Sale of Fund Shares

You may buy or sell shares of the Fund through a retirement plan, an investment professional, a broker-dealer, or other financial intermediary. You may purchase or redeem shares of the Fund on any day the New York Stock Exchange ("NYSE") is open, at the Fund's net asset value ("NAV") per share next calculated after your order is received in proper form, subject to any applicable sales charge. The Manager may, in its sole discretion, allow certain individuals to invest directly in the Fund. For more information regarding eligibility to invest directly please see "About Your Investment - Purchase and Redemption of Shares." Direct mutual fund account shareholders may buy subsequent shares or sell shares in various ways:

Tax Information

Dividends, capital gains distributions, and other distributions, if any,  that you receive as a result of your investment in the Fund are subject to federal income tax and may also be subject to state and local income taxes, unless you are a tax-exempt entity or your account is  tax-deferred,  such as an individual retirement account ("IRA") or a 401(k) plan (in which case you may be taxed later, upon the withdrawal of your investment from such account or plan).

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 and the Fund's distributor, Resolute Investment Distributors, Inc., or the Manager may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your individual financial professional to recommend the Fund over another investment. Ask your individual financial professional or visit your financial intermediary's website for more information.

6American Beacon Stephens Mid-Cap Growth Fund - Summary Prospectus