Prospectus by Investment Company (Form 497)

November 14, 2025

BNY MELLON INDEX FUNDS

BNY Mellon S&P 500 Index Fund

Supplement to Current Summary Prospectus and Prospectus

The following information supplements the information in the sections "Principal Investment Strategy" in the summary prospectus and "Fund Summary - Principal Investment Strategy" in the prospectus:

The fund may operate as a non-diversified fund, as defined under the Investment Company Act of 1940, as amended, to the approximate extent the S&P 500^®Index is non-diversified, without shareholder approval. The fund may therefore operate as non-diversified solely as a result of a change in relative market capitalization or index weighting of one or more constituents of the index.

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The following information supplements the information in the sections "Principal Risks" in the summary prospectus and "Fund Summary - Principal Risks" in the prospectus:

● Non-diversification risk. Because the fund seeks to closely track the composition of the index, from time to time, more than 25% of the fund's total assets may be invested in issuers representing more than 5% of the fund's total assets due to an index rebalance or market movement, which would result in the fund being non-diversified under the Investment Company Act of 1940, as amended. A non-diversified fund may invest a greater portion of its assets in securities of a smaller number of individual issuers than a diversified fund. As a result, the fund's performance may be more vulnerable to changes in the market value of a single issuer or group of issuers and more susceptible to risks associated with a single economic, political or regulatory occurrence than a diversified fund.

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The following information supplements the information in the section "Fund Details - Goal and Approach - BNY Mellon S&P 500 Index Fund" in the prospectus:

The fund may operate as a non-diversified fund, as defined under the Investment Company Act of 1940, as amended, to the approximate extent the S&P 500^®Index is non-diversified, without shareholder approval. The fund may therefore operate as non-diversified solely as a result of a change in relative market capitalization or index weighting of one or more constituents of the index. As a result, the fund may invest a significant percentage of its assets in a single issuer or small number of issuers.

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The following information supplements the information in the section "Fund Details - InvestmentRisks" in the prospectus:

BNY Mellon S&P 500 Index Fund also is subject to the following principal risk:

● Non-diversification risk. Because the fund seeks to closely track the composition of the index, from time to time, more than 25% of the fund's total assets may be invested in issuers

representing more than 5% of the fund's total assets due to an index rebalance or market movement, which would result in the fund being non-diversified under the Investment Company Act of 1940, as amended. A non-diversified fund may invest a greater portion of its assets in securities of a smaller number of individual issuers than a diversified fund. As a result, the fund's performance may be more vulnerable to changes in the market value of a single issuer or group of issuers and more susceptible to risks associated with a single economic, political or regulatory occurrence than a diversified fund.

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