"Happiness Is a Warm Gun" is a song by the English rock band the Beatles from their 1968 album The Beatles (also known as "the White Album"). It was written by John Lennon and credited to the Lennon–McCartney partnership. The song was composed into three distinct sections, referred by Lennon as "the Dirty Old Man", "the Junkie" and "the Gunman (Satire of '50s R&R)". He derived the title from an NRA magazine and explained that the lyrics were a double entendre for guns and his sexual desire for Yoko Ono.

Although tensions were high during the recording sessions for the White Album, the Beatles worked together as a unit to complete the song's challenging rhythmic issues and time signature changes. A demo of the song, recorded at George Harrison's Kinfauns home before the album's recording sessions, showed the song in its initial stage, with only a few portions present. He helped with the time signature changes through his knowledge of Indian classical music. The final portion of the song features backing vocals by Harrison and Paul McCartney. An excerpt from the demo was released on Anthology 3 in 1996, with the full demo being released on the super deluxe edition of the White Album in 2018.

Despite mixed reviews for the White Album on release, "Happiness Is a Warm Gun" was positively received by music critics, who highlighted the song's complex structure and lyrics for praise. All four Beatles identified it as their favourite song on the album. Nevertheless, it was banned by the BBC due to its sexually suggestive lyrics. The song has been covered by Tori Amos, U2 and the Breeders.