Who's Next is the fifth studio album by the English rock band the Who, released on 2 August 1971, by Track Records in the United Kingdom and Decca Records in the United States. It developed from the aborted Lifehouse project, a multi-media rock opera conceived by the group's guitarist Pete Townshend as a follow-up to the band's 1969 album Tommy. The project was cancelled owing to its complexity and to conflicts with Kit Lambert, the band's manager, but the group salvaged some of the songs, without the connecting story elements, to release as their next album. Eight of the nine songs on Who's Next were from Lifehouse, with the lone exception being the John Entwistle-penned "My Wife". Ultimately, the remaining Lifehouse tracks would all be released on other albums throughout the next decade.

The Who recorded Who's Next with assistance from recording engineer Glyn Johns. After producing the song "Won't Get Fooled Again" in the Rolling Stones Mobile Studio, they relocated to Olympic Studios to record and mix most of the album's remaining songs. They made prominent use of synthesizer on the album, particularly on "Won't Get Fooled Again" and "Baba O'Riley", which were both released as singles. The cover photo was shot by Ethan Russell; it made reference to the monolith in the 1968 film 2001: A Space Odyssey, as it featured the band standing by a concrete piling protruding from a slag heap in South Yorkshire, apparently having urinated against it.

The album was an immediate critical and commercial success and has since been viewed by many critics as the Who's best album, as well as one of the greatest albums of all time. It has been reissued on CD several times, often with additional songs originally intended for Lifehouse included as bonus tracks. Who's Next was ranked number 77 on Rolling Stone's 2020 edition of its "The 500 Greatest Albums of All Time" list.