A Perfect Circle is an American rock supergroup formed in 1999 by guitarist Billy Howerdel and Tool vocalist Maynard James Keenan. The band is known for their atypical music, which melds post-hardcore, progressive metal, and alternative rock with cinematic and soundtrack-inspired melodies.

Apart from the core line-up of Keenan and Howerdel, the group's full-time line-up has often changed since their formation, with drummers and bassists frequently joining and leaving the band. Primary album releases from the group include Mer de Noms (2000), Thirteenth Step (2003), and Emotive (2004). All three albums saw major Billboard success, with Emotive debuting at the number two spot on the Billboard 200 chart.

A Perfect Circle has also released several EPs, live albums, DVD's, and compilations to date, and has been praised for their youthful yet mature sound. In recent years