245 Summer Street

Fidelity® Investments

Boston, MA 02210

June 30, 2025

U.S. Securities & Exchange Commission

100 F Street, N.E.

Washington, D.C. 20549

Attention: File Room

RE: Fidelity Hereford Street Trust (the trust): File Nos. 033-52577 and 811-07139 Fidelity Flex Government Money Market Fund Fidelity Government Money Market Fund Fidelity Money Market Fund Fidelity Series Treasury Bill Index Fund Fidelity Treasury Digital Fund Fidelity Treasury Only Money Market Fund (the fund(s))

________________________________________________________________________

Ladies and Gentlemen:

Transmitted herewith pursuant to Rule 497(j) under the Securities Act of 1933 is certification that the Prospectus(es) and Statement(s) of Additional Information with respect to the above referenced fund(s) do not differ from those filed in the most recent post-effective amendment, which was filed electronically.

Very truly yours,

/s/Nicole Macarchuk

Nicole Macarchuk

Secretary of the Trust