The Who are an English rock band formed in London in 1964. Their classic line-up consisted of lead singer Roger Daltrey, guitarist and singer Pete Townshend, bass guitarist John Entwistle and drummer Keith Moon. They are considered one of the most influential rock bands of the 20th century, selling over 100 million records worldwide.

The Who developed from an earlier group, the Detours, and established themselves as part of the pop art and mod movements, featuring auto-destructive art by destroying guitars and drums on stage. Their first single as the Who, "I Can't Explain", reached the UK top ten, and was followed by a string of singles including "My Generation", "Substitute" and "Happy Jack". In 1967, they performed at the Monterey Pop Festival and released the US top ten single "I Can See for Miles", while touring extensively. The group's fourth album, 1969's rock opera Tommy, included the single "Pinball Wizard" and was a critical and commercial success. Live appearances at Woodstock and the Isle of Wight Festival, along with the live album Live at Leeds, cemented their reputation as a respected rock act. With their success came increased pressure on lead songwriter Townshend, and the follow-up to Tommy, Lifehouse, was abandoned. Songs from the project made up 1971's Who's Next, which included the hit "Won't Get Fooled Again". The group released the album Quadrophenia in 1973 as a celebration of their mod roots, and oversaw the film adaptation of Tommy in 1975. They continued to tour to large audiences before semi-retiring from live performances at the end of 1976. The release of Who Are You in 1978 was overshadowed by the death of Moon shortly after.

Kenney Jones replaced Moon and the group resumed activity, releasing a film adaptation of Quadrophenia and the retrospective documentary The Kids Are Alright. After Townshend became weary of touring, the group split in 1983. The Who occasionally re-formed for live appearances such as Live Aid in 1985, a 25th anniversary tour in 1989 and a tour of Quadrophenia in 1996–1997. They resumed regular touring in 1999, with drummer Zak Starkey. After Entwistle's death in 2002, plans for a new album were delayed. Townshend and Daltrey continued as the Who, releasing Endless Wire in 2006, and continue to play live regularly, with Starkey, bassists Pino Palladino (2006–2017) and Jon Button (2017–present), and guitarist Simon Townshend (Pete's brother) serving as touring players. A tour with a complete symphony orchestra, along with the release of a twelfth studio album, both occurred in 2019.

The Who's major contributions to rock music include the development of the Marshall stack, large PA systems, use of the synthesizer, Entwistle and Moon's lead playing styles, Townshend's feedback and power chord guitar technique, and the development of the rock opera. They are cited as an influence by hard rock, punk rock and mod bands, and their songs still receive regular exposure.