"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.
American Public Media's business-news program, Marketplace, uses a portion of Fats Waller's version to open its weekly letters-from-listeners segment.
The song had a major revival in 1957 in a Coral recording (on April 3) by Billy Williams with orchestra directed by Dick Jacobs.
Among other versions are recordings by The Boswell Sisters, Connee Boswell, Nat King Cole, Scatman Crothers, Gregory Isaacs, Barry Manilow, Dean Martin, Anne Murray, Willie Nelson, Linda Scott, Shakin' Stevens, Al Bowlly, Sarah Vaughan, Ella Mae Morse, and The Mills Brothers.
Don Cherry, best known for "Band of Gold", his 1955 mega hit, released a version of 'Letter' in 1957 on a Coronet 78 (an Australian label), working with Ray Conniff and his Orchestra.