(American Beacon Stephens Mid-Cap Growth Fund℠)

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Investment Objective </b></div>

The Fund seeks long-term growth of capital.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Fees and Expenses of the Fund </b></div>

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. More information is available from your financial professional.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"> <b>Shareholder Fees (fees paid directly from your investment)</b></div>

Shareholder Fees - (American Beacon Stephens Mid-Cap Growth Fund℠)	Class R6
Maximum sales charge imposed on purchases (as a percentage of offering price)	none
Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)	none

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"> <b>Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)</b></div>

Annual Fund Operating Expenses - (American Beacon Stephens Mid-Cap Growth Fund℠)	Class R6
Management Fee	0.80%
Distribution (12b-1) Fees	none
Other Expenses	0.19%	[1]
Total Annual Fund Operating Expenses	0.99%
Fee Waiver and/or expense reimbursement	(0.15%)	[2]
Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement	0.84%

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b>Example</b></div>

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 the R6 Class shares through April 30, 2020. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Expense Example - (American Beacon Stephens Mid-Cap Growth Fund℠)	1 Year	3 Years	5 Years	10 Years
Class R6 | USD ($)	86	295	527	1,195

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Portfolio Turnover </b></div>

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 24% of the average value of its portfolio.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Principal Investment Strategies </b></div>

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of medium capitalization companies. The Fund considers a company to be a medium capitalization company if it has a market capitalization (stock market worth), at the time of investment, between $1 billion and the market capitalization of the largest company in the Russell Midcap® Index, which was $36.7 billion as of December 31, 2017.

Most of the assets of the Fund are invested in U.S. common stocks that Stephens Investment Management Group, LLC ("SIMG") believes have clear indicators of future earnings growth, or that demonstrate other potential for growth of capital. The Fund may invest in other securities, including preferred stock, securities convertible into common stock, U.S dollar denominated foreign stock traded on U.S. exchanges, American Depositary Receipts ("ADRs") and real estate investment trusts ("REITs"). The Fund also may invest in stocks of large-capitalization companies. In selecting companies for the Fund, SIMG employs quantitative analysis and fundamental research with a focus on earnings growth. 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, based on portfolio positioning to reflect its benchmark index, the Fund may have significant positions in particular sectors. The Fund may have significant exposure to 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 money market funds, and may lend its securities to broker-dealers and other institutions to earn additional income.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Principal Risks </b></div>

There is no assurance that the Fund will achieve its investment objectives 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 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 are:

Cybersecurity and Operational Risk
The Fund and its service providers, and shareholders' ability to transact with the Fund, may be negatively impacted due to operational risks arising from, among other problems, human errors, systems and technology disruptions or failures, or cybersecurity incidents. Cybersecurity incidents may allow an unauthorized party to gain access to Fund assets, customer data, or proprietary information, or cause the Fund or its service providers, as well as the securities trading venues and their service providers, to suffer data corruption or lose operational functionality. 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. Most issuers in which the Fund invests are heavily dependent on computers for data storage and operations, and require ready access to the internet to conduct their business. Thus, cybersecurity incidents could also affect issuers of securities in which the Fund invests, leading to significant loss of value.

Equity Investments Risk
Equity securities are subject to investment and market risk. The Fund's investments in equity securities may include common stocks, preferred stocks, securities convertible into or exchangeable for common stocks, REITs, depositary receipts and U.S. dollar-denominated foreign stocks traded on U.S. exchanges. Such investments may expose the Fund to additional risks.

• Common Stock. The value of a company's common stock may fall as a result of factors affecting the company, companies in the same industry or sector, or the financial markets overall. Common stock generally is subordinate to preferred stock upon the liquidation or bankruptcy of the issuing company.

• Convertible Securities. Convertible securities are subject to the risk that the credit standing of the issuer may have an effect on the convertible securities' investment value. Convertible securities are also sensitive to movements in interest rates.

• Depositary Receipts. Depositary receipts and U.S. dollar-denominated foreign stocks traded on U.S. exchanges are subject to certain of the risks associated with investing directly in foreign securities, including, but not limited to, currency exchange rate fluctuations, political and financial instability in the home country of a particular depositary receipt or foreign stock, less liquidity and more volatility, less government regulation and supervision and delays in transaction settlement.

• Preferred Stock. Preferred stocks are sensitive to movements in interest rates. Preferred stocks may be less liquid than common stocks and, unlike common stocks, participation in the growth of an issuer may be limited. Distributions on preferred stocks generally are payable at the discretion of an issuer and after required payments to bond holders.

• REITs. Investments in REITs are subject to the risks associated with investing in the real estate industry such as adverse developments affecting the real estate industry and real property values. REITs also are dependent upon the skills of their managers and are subject to heavy cash flow dependency or self-liquidation. Domestic REITs could be adversely affected by failure to qualify for tax-free "pass-through" of distributed net income and net realized gains under the Internal Revenue Code of 1986, as amended ("Internal Revenue Code"), or to maintain their exemption from registration under the Investment Company Act of 1940, as amended ("Investment Company Act"). REITs typically incur fees that are separate from those incurred by the Fund. Accordingly, the Fund's investment in REITs will result in the layering of expenses such that shareholders will indirectly bear a proportionate share of the REITs' operating expenses, in addition to paying Fund expenses. The value of REIT common stock may decline when interest rates rise.

Foreign Investing Risk
Non-U.S. investments carry potential risks not associated with U.S. investments. Such risks include, but are not limited to: (1) currency exchange rate fluctuations, (2) political and financial instability, (3) less liquidity, (4) lack of uniform accounting, auditing and financial reporting standards, (5) increased volatility, (6) different government regulation and supervision of foreign stock exchanges, brokers and listed companies, and (7) delays in transaction settlement in some foreign markets.

Growth Companies Risk
Growth companies are expected to increase their earnings at a certain rate. When these expectations are not met, the prices of these stocks may go down, even if earnings showed an absolute increase. Growth company stocks may lack the dividend yield that can cushion stock prices 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 which 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 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. The value of a security may decline due to general market conditions which are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investment sentiment generally. Changes in the financial condition of a single issuer can impact a market as a whole. A rise in protectionist trade policies, and the possibility of changes to some international trade agreements, could affect the economies of many nations in ways that cannot necessarily be foreseen at the present time.

Mid-Capitalization Companies Risk
Investing in the securities of mid-capitalization companies involves greater risk and the possibility of greater price volatility than investing in larger capitalization and more established companies. Since mid-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 expected changes in interest rates, borrowing costs and earnings.

Other Investment Companies Risk
The Fund may invest in shares of other registered investment companies, including money market funds. 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 and will be subject to the risks associated with investments in those companies. For example, money market funds are subject to interest rate risk, credit risk, and market risk.

Sector Risk
When the Fund focuses its investments in certain sectors of the economy, its performance may be driven largely by sector performance and could fluctuate more widely than if the Fund were invested more evenly across sectors.

• Information Technology Sector Risk. The market prices of information technology-related securities tend to exhibit a greater degree of market risk and sharp price fluctuations than other types of securities. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices.

Securities Lending Risk
To the extent the Fund lends its securities, it may be subject to the following risks: i) borrowers of the Fund's securities typically provide collateral in the form of cash that is reinvested in securities, ii) the securities in which the collateral is invested may not perform sufficiently to cover the return collateral payments owed to borrowers, iii) delays may occur in the recovery of securities from borrowers, which could interfere with the Fund's ability to vote proxies or to settle transactions, and iv) there is the risk of possible loss of rights in the collateral should the borrower fail financially.

Securities Selection Risk
Securities selected by the sub-advisor or the Manager for the Fund may not perform to expectations. This could result in the Fund's underperformance compared to other funds with similar investment objectives.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"><b> Fund Performance </b></div>

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 performance of the Fund's Investor Class shares, which are not offered in this Prospectus, has varied from year to year. The table discloses how the performance of the Fund's Investor Class shares compares to a broad-based market index, which is the Fund's benchmark index, for the periods indicated.

The Investor Class shares of the Fund have adopted the performance history and financial statements of the Class A shares of the Fund's predecessor. The performance shown for the Investor Class shares of the Fund represents the performance of the Class A shares of the Fund's predecessor from January 1, 2008 through February 23, 2012, and the performance of the Investor Class shares of the Fund from February 24, 2012 through December 31, 2017. The Investor Class shares would have had similar annual returns to the predecessor Fund's Class A shares because the shares of each class represent investments in the same portfolio securities. However, the predecessor Fund's Class A shares had different expenses than the Investor Class shares, which would affect performance.

Performance information for the R6 Class shares of the Fund is not provided because the R6 Class had not commenced operations prior to the date of this Prospectus. The R6 Class shares would have had similar annual returns to the Investor Class shares because the shares of each class represent investments in the same portfolio securities. However, the Fund's Investor Class shares have different expenses than the Fund's R6 Class shares, which would affect performance.

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.

<div style="font-size:10pt;padding-top:2;padding-bottom:0;padding-left:0;"> <b>Calendar year total returns for Investor Class Shares. Year Ended 12/31</b></div>

Highest Quarterly Return:
16.31% 3rd Quarter 2009
01/01/2008 through 12/31/2017

Lowest Quarterly Return:
-28.39% 4th Quarter 2008
01/01/2008 through 12/31/2017

Average Annual Total Returns - (American Beacon Stephens Mid-Cap Growth Fund℠)	Inception Date	1 Year	5 Years	10 Years
Investor Class	Feb. 01, 2006	27.97%	12.85%	7.66%
Investor Class | Returns After Taxes on Distributions	Feb. 01, 2006	26.42%	11.39%	6.95%
Investor Class | Returns After Taxes on Distributions and Sales of Fund Shares	Feb. 01, 2006	17.12%	10.06%	6.12%
Russell Midcap Growth Index (Reflects no deduction for fees, expenses, or taxes)		25.27%	15.30%	9.10%

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; after-tax returns for other share classes will vary.

[1] Other Expenses are based on estimated expenses for the current fiscal year.

[2] American Beacon Advisors, Inc. (the "Manager") has contractually agreed to waive fees and/or reimburse expenses of the Fund's R6 Class shares through April 30, 2020 to the extent that Total Annual Fund Operating Expenses exceed 0.84%% for the R6 Class (excluding taxes, interest, brokerage commissions, acquired fund fees and expenses, securities lending fees, expenses associated with securities sold short, litigation, and other extraordinary expenses). The contractual expense reimbursement can be changed or terminated only in the discretion and with the approval of a majority of the Fund's Board of Trustees. The Manager can be reimbursed by the Fund for any contractual fee waivers or expense reimbursements if reimbursement to the Manager (a) occurs within three years after the Manager's own waiver or reimbursement and (b) does not cause the Total Annual Fund Operating Expenses of a class to exceed the lesser of the contractual percentage limit in effect at the time of the waiver/reimbursement or the time of the recoupment.