Securities Act of 1933 Registration No. 033-52577

Investment Company Act of 1940 Registration No. 811-07139

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 [X]

[ ] Pre-Effective Amendment No.  ______

[X] Post-Effective Amendment No.  __76___

and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 [X]

[X] Amendment No.  __76___

Fidelity Hereford Street Trust

 (Exact Name of Registrant as Specified in Charter)

245 Summer Street, Boston, Massachusetts 02210

(Address of Principal Executive Offices)(Zip Code)

Registrant’s Telephone Number: 617-563-7000

Nicole Macarchuk, Secretary and Chief Legal Officer

245 Summer Street

Boston, Massachusetts 02210

(Name and Address of Agent for Service)

[X] This Post-Effective Amendment designates a new effective date for a previously filed post-effective amendment.

The purpose of this Post-Effective Amendment is to designate a new effective date, June 27, 2025, for the Post-Effective Amendment previously filed on March 21, 2025, for the fund(s).

The Prospectus(es) and Statement(s) of Additional Information (SAI) for the fund(s) are identical to those filed in Post-Effective Amendment No. _75__, the Part C is identical to the Part C filed in Post-Effective Amendment No. _75__, and the Prospectus(es), SAI(s), and Part C are incorporated herein in their entirety by reference to those previously filed Post-Effective Amendments.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for the effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment No.76to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, and Commonwealth of Massachusetts, on the 29th day of May 2025.

Fidelity Hereford Street Trust
By	/s/Laura M. Del Prato Laura M. Del Prato, President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

(Signature)		(Title)	(Date)
/s/Laura M. Del Prato		President and Treasurer	May 29, 2025
Laura M. Del Prato		(Principal Executive Officer)
/s/Stephanie Caron		Chief Financial Officer	May 29, 2025
Stephanie Caron		(Principal Financial Officer)
/s/Abigail P. Johnson	†	Trustee	May 29, 2025
Abigail P. Johnson
/s/Elizabeth S. Acton	*	Trustee	May 29, 2025
Elizabeth S. Acton
/s/Laura M. Bishop	*	Trustee	May 29, 2025
Laura M. Bishop
/s/Ann E. Dunwoody	*	Trustee	May 29, 2025
Ann E. Dunwoody
/s/Robert F. Gartland	*	Trustee	May 29, 2025
Robert F. Gartland
/s/Robert W. Helm	*	Trustee	May 29, 2025
Robert W. Helm
/s/Mark A. Murray	*	Trustee	May 29, 2025
Mark A. Murray
/s/Jennifer Toolin McAuliffe	*	Trustee	May 29, 2025
Jennifer Toolin McAuliffe
/s/Lester Owens	*	Trustee	May 29, 2025
Lester Owens
/s/Christine J. Thompson	*	Trustee	May 29, 2025
Christine J. Thompson
/s/Carol J. Zierhoffer	*	Trustee	May 29, 2025
Carol J. Zierhoffer

†	By:	/s/ Stephanie J. Brown
		Stephanie J. Brown, pursuant to a power of attorney dated January 26, 2023 and filed herewith.
*	By:	/s/Megan C. Johnson
		Megan C. Johnson, pursuant to a power of attorney dated May 1, 2025 and filed herewith.

POWER OF ATTORNEY

I, the undersigned Trustee of the following investment companies:

Fidelity Aberdeen Street Trust	Fidelity Municipal Trust
Fidelity Advisor Series II	Fidelity Municipal Trust II
Fidelity Advisor Series IV	Fidelity Newbury Street Trust
Fidelity California Municipal Trust	Fidelity New York Municipal Trust
Fidelity California Municipal Trust II	Fidelity New York Municipal Trust II
Fidelity Central Investment Portfolios II LLC	Fidelity Oxford Street Trust
Fidelity Charles Street Trust	Fidelity Oxford Street Trust II
Fidelity Colchester Street Trust	Fidelity Phillips Street Trust
Fidelity Court Street Trust	Fidelity Revere Street Trust
Fidelity Court Street Trust II	Fidelity Salem Street Trust
Fidelity Garrison Street Trust	Fidelity School Street Trust
Fidelity Hereford Street Trust	Fidelity Union Street Trust
Fidelity Income Fund	Fidelity Union Street Trust II
Fidelity Massachusetts Municipal Trust	Variable Insurance Products Fund V
Fidelity Merrimack Street Trust

in addition to any other Fidelity Fund for which the undersigned individual serves as Trustee (collectively, the "Funds"), hereby constitute and appoint Stephanie J. Brown, my true and lawful attorney- in-fact, with full power of substitution, and with full power to sign for me and in my name in the appropriate capacity, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post- Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in my name and behalf in connection therewith as said attorney-in-fact deems necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission. I hereby ratify and confirm all that said attorney-in-fact or her substitutes may do or cause to be done by virtue hereof.

This Power of Attorney shall remain in full force and effect only for such time as Stephanie J. Brown shall continue to be an officer of Fidelity Management & Research Company LLC, provided that, notwithstanding the foregoing, this Power of Attorney may be revoked at any time by the undersigned in writing.

This Power of Attorney has been executed as of January 26, 2023.

/s/ Abigail P. Johnson

Abigail P. Johnson

POWER OF ATTORNEY

We, the undersigned Directors or Trustees, as the case may be, of the following investment companies:

Fidelity Aberdeen Street Trust Fidelity Advisor Series II Fidelity Advisor Series IV Fidelity Boylston Street Trust Fidelity California Municipal Trust Fidelity California Municipal Trust II Fidelity Central Investment Portfolios II LLC Fidelity Charles Street Trust Fidelity Colchester Street Trust Fidelity Court Street Trust Fidelity Court Street Trust II Fidelity Garrison Street Trust Fidelity Hereford Street Trust Fidelity Income Fund Fidelity Massachusetts Municipal Trust Fidelity Merrimack Street Trust Fidelity Money Market Trust Fidelity Municipal Trust Fidelity Municipal Trust II Fidelity Newbury Street Trust Fidelity New York Municipal Trust Fidelity New York Municipal Trust II Fidelity Oxford Street Trust Fidelity Oxford Street Trust II Fidelity Phillips Street Trust Fidelity Revere Street Trust Fidelity Salem Street Trust Fidelity School Street Trust Fidelity Union Street Trust Fidelity Union Street Trust II Variable Insurance Products Fund V

in addition to any other Fidelity Fund for which the undersigned individuals serve as Directors or Trustees (collectively, the “Funds”), hereby revoke all previous powers of attorney we have given to sign and otherwise act in our names and behalf in matters involving any investment company for which FMR or an affiliate acts as investment adviser and hereby constitute and appoint Thomas C. Bogle, John V. O’Hanlon, Megan C. Johnson, and Anthony H. Zacharski, each of them singly, our true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for us and in our names in the appropriate capacities, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in our names and behalf in connection therewith as said attorneys-in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission.  We hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof.  This power of attorney is effective for all documents filed on or after May 1, 2025.

WITNESS our hands on this first day of May 2025.

/s/Elizabeth S. Acton	/s/Mark A. Murray
Elizabeth S. Acton	Mark A. Murray
/s/Laura M. Bishop	/s/Jennifer Toolin McAuliffe
Laura M. Bishop	Jennifer Toolin McAuliffe
/s/Ann E. Dunwoody	/s/Lester Owens
Ann E. Dunwoody	Lester Owens
/s/Robert F. Gartland	/s/Christine J. Thompson
Robert F. Gartland	Christine J. Thompson
/s/Robert W. Helm	/s/Carol J. Zierhoffer
Robert W. Helm	Carol J. Zierhoffer