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Prospectus:

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Supplement Text Block

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American Beacon Stephens Small Cap Growth Fund

Supplement dated August 23, 2019

to the

Prospectus and Summary Prospectus dated April 30, 2019

On August 20, 2019, the Board of Trustees of American Beacon Funds (the "Trust") approved: (i) an amendment to the existing investment advisory agreement among American Beacon Advisors, Inc., Stephens Investment Management Group, LLC ("Stephens") and the Trust, on behalf of the American Beacon Stephens Small Cap Growth Fund (the "Fund"), whereby the fee rate payable to Stephens by the Fund with respect to the first $200 million in assets under management will be 0.60% and thereafter the fee rate payable to Stephens by the Fund will be 0.55%, effective on or about September 1, 2019; (ii) the addition of contractual expense ratio caps for the Fund's A Class, C Class, Y Class, Institutional Class and Investor Class shares, effective on or about September 1, 2019; and (iii) the lowering of the contractual expense ratio cap for the Fund's R6 Class shares, effective on or about September 1, 2019. Accordingly, the changes set forth below are effective on or about September 1, 2019:

1. In the "Fund Summaries – Fees and Expenses of the Fund" section, the tables below the first paragraph are deleted and replaced with the following:

Shareholder Fees (fees paid directly from your investment)
Share Class	A	C	Y	R6	Institutional	Investor
Maximum sales charge imposed on purchases (as a percentage of offering price)	5.75%	None	None	None	None	None
Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)	0.50%1	1.00%	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	C	Y	R6	Institutional	Investor
Management Fees2	0.93%	0.93%	0.93%	0.93%	0.93%	0.93%
Distribution (12b-1) Fees	0.25%	1.00%	0.00%	0.00%	0.00%	0.00%
Other Expenses	0.15%	0.17%	0.17%	0.12%3	0.11%	0.40%
Total Annual Fund Operating Expenses	1.33%	2.10%	1.10%	1.05%	1.04%	1.33%
Fee Waiver and/or expense reimbursement4	(0.05)%	(0.04)%	(0.04)%	(0.10)%	(0.05)%	(0.02)%
Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement	1.28%	2.06%	1.06%	0.95%	0.99%	1.31%

1	A contingent deferred sales charge (''CDSC'') of 0.50% will be charged on certain purchases of $1,000,000 or more of A Class shares that are redeemed in whole or part within 18 months of purchase.
2	The management fee has been restated to reflect the current contractual fee rate.
3	Other Expenses for R6 Class shares are based on estimated expenses for the current fiscal year.
4	American Beacon Advisors, Inc. (the "Manager") has contractually agreed to waive fees and/or reimburse expenses of the Fund's A Class, C Class, Y Class, R6 Class, Institutional Class and Investor Class shares, as applicable, through April 30, 2021 to the extent that Total Annual Fund Operating Expenses exceed 1.28% for the A Class, 2.06% for the C Class, 1.06% for the Y Class, 0.95% for the R6 Class, 0.99% for the Institutional Class and 1.31% for the Investor 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.

2. The "Fund Summaries – Fees and Expenses of the Fund - Example" section is deleted and replaced with the following:

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 the Example reflects the fee waiver/expense reimbursement arrangement for each share class through April 30, 2021. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Share Class	1 Year	3 Years	5 Years	10 Years
A	$698	$964	$1,254	$2,077
C	$309	$651	$1,122	$2,425
Y	$108	$343	$600	$1,334
R6	$97	$317	$562	$1,265
Institutional	$101	$323	$566	$1,263
Investor	$133	$418	$726	$1,598

Assuming no redemption of shares:

Share Class	1 Year	3 Years	5 Years	10 Years
C	$209	$651	$1,122	$2,425

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund)

Prospectus:

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Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

April 30, 2021

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses for R6 Class shares are based on estimated expenses for the current fiscal year.

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

A contingent deferred sales charge (''CDSC'') of 0.50% will be charged on certain purchases of $1,000,000 or more of A Class shares that are redeemed in whole or part within 18 months of purchase.

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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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 the Example reflects the fee waiver/expense reimbursement arrangement for each share class through April 30, 2021. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

Assuming no redemption of shares:

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Class A

Prospectus:

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Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

0.50%

^[1]

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other Expenses

rr_OtherExpensesOverAssets

0.15%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.33%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.28%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 698

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

964

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,254

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 2,077

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Class C

Prospectus:

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Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

1.00%

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other Expenses

rr_OtherExpensesOverAssets

0.17%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

2.10%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

2.06%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 309

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

651

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

1,122

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

2,425

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

209

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

651

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

1,122

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 2,425

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Class Y

Prospectus:

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Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.17%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.10%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.06%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 108

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

343

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

600

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,334

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Class R6

Prospectus:

rr_ProspectusTable

Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.12%

^[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.05%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.10%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.95%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 97

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

317

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

562

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,265

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Institutional Class

Prospectus:

rr_ProspectusTable

Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.11%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.04%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.99%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 101

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

323

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

566

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,263

(American Beacon Funds - Supplement) | (American Beacon Stephens Small Cap Growth Fund) | Investor Class

Prospectus:

rr_ProspectusTable

Maximum sales charge imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (as a percentage of the lower of original offering price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

Management Fees

rr_ManagementFeesOverAssets

0.93%

^[2]

Distribution (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.40%

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.33%

Fee Waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[3]

Total Annual Fund Operating Expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.31%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 133

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

418

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

726

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

$ 1,598

[1] A contingent deferred sales charge (''CDSC'') of 0.50% will be charged on certain purchases of $1,000,000 or more of A Class shares that are redeemed in whole or part within 18 months of purchase.

[2] The management fee has been restated to reflect the current contractual fee rate.

[3] American Beacon Advisors, Inc. (the "Manager") has contractually agreed to waive fees and/or reimburse expenses of the Fund's A Class, C Class, Y Class, R6 Class, Institutional Class and Investor Class shares, as applicable, through April 30, 2021 to the extent that Total Annual Fund Operating Expenses exceed 1.28% for the A Class, 2.06% for the C Class, 1.06% for the Y Class, 0.95% for the R6 Class, 0.99% for the Institutional Class and 1.31% for the Investor 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.

[4] Other Expenses for R6 Class shares are based on estimated expenses for the current fiscal year.