Investment Manager Series Trust III

235 W. Galena Street

Milwaukee, Wisconsin 53212

February 3, 2026

VIA EDGAR TRANSMISSION

U.S. Securities and Exchange Commission

Division of Investment Management

100 “F” Street, N.E.

Washington, DC  20549

Dear Sir or Madam:

Pursuant to Rule 497(j) under the Securities Act of 1933, as amended, please accept this letter as certification that the Prospectus and Statement of Additional Information for the FPA New Income Fund, a series of the Trust, does not differ from that contained in Post-Effective Amendment No. 139 to the Trust’s Registration Statement on Form N-1A which was filed electronically on January 26, 2026.

If you have any questions or require further information, please contact me at (626) 385-5777 or diane.drake@mfac-ca.com.