"Sgt. Pepper's Lonely Hearts Club Band" is a song written by Paul McCartney (credited to Lennon–McCartney), and first recorded and released in 1967, on the album of the same name by the Beatles. The song appears twice on the album: as the opening track (segueing into "With a Little Help from My Friends"), and as "Sgt. Pepper's Lonely Hearts Club Band (Reprise)", the penultimate track (segueing into "A Day in the Life"). As the title song, the lyrics introduce the fictional band that performs on the album.

Since its original album release, "Sgt. Pepper's Lonely Hearts Club Band" has also been released on various Beatles singles and compilation albums. The song has also been performed by several other artists, including Jimi Hendrix, U2, and a comic interpretation by Bill Cosby, using the opening to John Philip Sousa's Washington Post March as the instrumental bridge.

In November 1966, on the flight back to England after a holiday, McCartney conceived an idea in which an entire album would be role-played, with each of the Beatles assuming an alter-ego in the "Lonely Hearts Club Band", which would then perform a concert in front of an audience. The inspiration is said to have come when roadie Mal Evans innocently asked McCartney what the letters "S" and "P" stood for on the pots on their in-flight meal trays, and McCartney explained it was for salt and pepper. This then led to the Sgt. Pepper's Lonely Hearts Club Band concept, as well as the song.

The group's road manager, Neil Aspinall, suggested the idea of Sgt. Pepper being the compère, as well as the reprise at the end of the album. According to his diaries, Evans may have also contributed to the song. John Lennon attributed the idea for Sgt. Pepper to McCartney, although the song is officially credited to Lennon–McCartney. The Beatles recorded the track in Abbey Road's studio 2, with George Martin producing, and Geoff Emerick engineering. Work on the song started on 1 February 1967, and after three further sessions the recording was completed on 6 March 1967.

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