Keith John Moon (23 August 1946 – 7 September 1978) was an English musician who was the drummer for the rock band the Who. Regarded as one of the greatest drummers in the history of rock music, he was noted for his unique style of playing and his eccentric, often self-destructive behaviour.

Moon grew up in Wembley and took up the drums during the early 1960s. After playing with a local band, the Beachcombers, he joined the Who in 1964 before they recorded their first single. Moon was recognised for his drumming style, which emphasised tom-toms, cymbal crashes, and drum fills. Throughout his tenure with the Who, his drum kit steadily grew in size, and (along with Ginger Baker) he has been credited as one of the earliest rock drummers to regularly employ double bass drums in his setup. Moon occasionally collaborated with other musicians and later appeared in films, but considered playing in the Who his primary occupation, and remained a member of the band until his death. In addition to his talent as a drummer, Moon developed a reputation for smashing his kit on stage and destroying hotel rooms on tour. He was fascinated with blowing up toilets with cherry bombs or dynamite, and destroying television sets. Moon also enjoyed touring and socialising, and became bored and restless when the Who were inactive. His 21st birthday party in Flint, Michigan, has been cited as a notorious example of decadent behaviour by rock groups.

Moon suffered a number of setbacks during the 1970s, most notably the accidental death of chauffeur Neil Boland and the breakdown of his marriage. He suffered from alcoholism and acquired a reputation for decadence and dark humour; his nickname was "Moon the Loon". While touring with the Who, on several occasions he passed out on stage and was hospitalised. By the time of their final tour with him in 1976, and particularly during production of the studio album Who Are You (1978) and the concert film The Kids Are Alright, his deterioration was evident. Moon moved back to London from Los Angeles in 1978, dying that September from an overdose of clomethiazole, a drug intended to treat or prevent symptoms of alcohol withdrawal.

Moon's drumming continues to be praised by critics and musicians. He was posthumously inducted into the Modern Drummer Hall of Fame in 1982, becoming the second rock drummer to be chosen, and in 2011 he was voted the second-greatest drummer in history by a Rolling Stone readers' poll. Moon was inducted into the Rock and Roll Hall of Fame in 1990 as a member of the Who.