"I'm Gonna Sit Right Down and Write Myself a Letter" is a 1935 popular song with music by Fred E. Ahlert and lyrics by Joe Young. It has been recorded many times, and has become a standard of the Great American Songbook. It is one of several songs from the Harlem Renaissance featured in the Broadway musical Ain't Misbehavin'. American Public Media's business-news program, Marketplace, uses a portion of Fats Waller's version to open its weekly letters-from-listeners segment.