King Crimson is a musical group founded by guitarist Robert Fripp and drummer Michael Giles in 1969. They have typically been categorised as progressive rock, although they incorporate diverse influences ranging from jazz, classical, and experimental music to psychedelic, New Wave, hard rock, gamelan, and folk music. King Crimson has garnered little radio or music video airplay, but gained a large cult following. Their debut album, In the Court of the Crimson King, is widely regarded as a landmark in progressive rock. Their later excursions into even more unconventional territory have been influential on many contemporary musical artists.

In the late-1960s, the band were influential in popularising a previously unexplored mellotron rock style. Throughout the early 1970s, King Crimson's membership fluctuated as the band explored elements of jazz and funk. The band developed an improvisational sound influenced by hard rock and became a more stable unit in the mid-1970s, before their initial break up in 1974. The band reformed in 1981 for three years, influenced by new wave and gamelan music, before breaking up again for around a decade. Following their 1994 reunion, King Crimson blended aspects of their 1980s and 1970s sound, which has continued into the 21st century.

King Crimson's membership has fluctuated considerably throughout their existence, with 18 musicians and two lyricists passing through the ranks as full band members. Robert Fripp, the only constant member of King Crimson, has arranged several disparate lineups of the band, and he has stated that he does not necessarily consider himself the band's leader. He describes King Crimson as "a way of doing things", and notes that he never originally intended to be seen as the head of the group.