"Day Tripper" is a song by the English rock band the Beatles that was released as a double A-side single with "We Can Work It Out" in December 1965. The song was written primarily by John Lennon with some contributions from Paul McCartney and was credited to the Lennon–McCartney partnership. Both songs were recorded during the sessions for the band's Rubber Soul album. The single topped charts in Britain, Ireland, the Netherlands and Norway. In the United States, "Day Tripper" peaked at number five on the Billboard Hot 100 chart and "We Can Work It Out" held the top position.

"Day Tripper" is a rock song based around an electric guitar riff and drawing on the influence of American soul music. The Beatles included it in their concert set-list until their retirement from live performances in late August 1966. The single was the first example of a double A-side in Britain. Its success popularised the format and, in giving equal treatment to two songs, allowed recording artists to show their versatility. The band's use of promotional films to market the single anticipated the modern music video.

In the UK, "Day Tripper" / "We Can Work It Out" was the seventh highest selling single of the 1960s. As of December 2018, it was the 54th best-selling single of all time in the UK – one of six Beatles singles included in the top sales rankings published by the Official Charts Company.