One After 909

One After 909 is a song by The Beatles, written primarily by John Lennon (credited to Lennon/McCartney) and originally released in 1970 (see 1970 in music) on the album Let It Be. The album version is the live performance from the rooftop concert which took place on 30 January 1969. This performance is also included in the Let It Be film. The song was written as early as 1957, and is one of the first Lennon-McCartney compositions.

The Beatles originally attempted to record the song on 5 March 1963 during the same session that produced their third single, "From Me to You", and its B-side "Thank You Girl". They were unhappy with the result and that version was not released at the time. Various takes from the 5 March session, and an edit of them, were released in 1995 on the Anthology 1 compilation. Episode 1 of the Beatles Anthology features a recording of the song made in 1960.

"One After 909" is included on 2003's Let It Be... Naked, a remixed and remastered version of the original 1970 session tapes.

Each version of the song is representative of the Beatles changing styles, with the 1963 recording based on a simple 12-bar structure with few lead parts other than George Harrison's solo in the middle. The 1969 recording is much faster and heavier, with Harrison playing lead riffs throughout.

On the rooftop version released on Let It Be, either Harrison or Lennon plays an incorrect first note, resulting in an flat, atonal start. This was one of the many errors corrected for Let It Be... Naked.

Also on the Let It Be version of this song, Lennon is heard singing the opening lines to "Danny Boy" as the song fades out.