"When I'm Sixty-Four" is a song by the English rock band The Beatles, written by Paul McCartney (credited to Lennon–McCartney) and released on their 1967 album Sgt. Pepper's Lonely Hearts Club Band. McCartney wrote the song when he was about 14, probably in April or May 1956, and it was one of the first songs he ever wrote. The song was recorded in a key different from the final recording; it was sped up at the request of McCartney to make his voice sound younger. It prominently features a trio of clarinets (two regular clarinets and one bass clarinet) throughout.
Paul McCartney wrote the melody to "When I'm Sixty-Four" around the age of 14, probably at 20 Forthlin Road in April or May 1956. In 1987, McCartney recalled, "Rock and roll was about to happen that year, it was about to break, [so] I was still a little bit cabaret minded", and in 1974, "I wrote a lot of stuff thinking I was going to end up in the cabaret, not realizing that rock and roll was particularly going to happen. When I was fourteen there wasn't much of a clue that it was going to happen."
The song is sung by a young man to his lover, and is about his plans of their growing old together. Although the theme is ageing, it was one of the first songs McCartney wrote. Beatles historian Mark Lewisohn suggests it was McCartney's second composition, coming after "Call It Suicide" but before "I Lost My Little Girl". It was in the Beatles' setlist in their early days as a song to perform when their amplifiers broke down or the electricity went off. Both George Martin and Lewisohn speculated that McCartney may have thought of the song when recording began for Sgt. Pepper's Lonely Hearts Club Band in December 1966 because his father, Jim McCartney, turned 64 earlier that year.
In 1967, John Lennon said of the song, "Paul wrote it in the Cavern days. We just stuck a few more words on it like 'grandchildren on your knee' and 'Vera, Chuck and Dave' ... this was just one that was quite a hit with us.