A Perfect Circle is an American rock band formed in Los Angeles, California in 1999 by guitarist Billy Howerdel and Tool vocalist Maynard James Keenan. A Perfect Circle released three of their four studio albums in the early 2000s: their debut Mer de Noms in 2000, a follow-up, Thirteenth Step in 2003; and an album of radically re-worked cover songs, Emotive, in 2004. Shortly after Emotive's release, the band went on hiatus; Keenan returned to Tool and started up solo work under the band name Puscifer, while Howerdel released a solo album, Keep Telling Myself It's Alright, under the moniker Ashes Divide. Band activity was sporadic in the following years; the band reformed in 2010, and played live shows on and off between 2010 and 2013, but fell into inactivity after the release of their greatest hits album, Three Sixty, and a live album box set, A Perfect Circle Live: Featuring Stone and Echo in late 2013. The band reformed in 2017 to record a fourth album, Eat the Elephant, which was released in 2018. After spending the rest of the year touring in support of the album, the band fell into inactivity until 2024 for a brief tour and one-off song "Kindred".

Prone to downtime due to Keenan's other musical commitments, the band has featured a variety of musicians throughout alternating periods of activity and inactivity, and has changed line-ups on each album, leaving Keenan and Howerdel the only constant members. The original incarnation of the band included Paz Lenchantin on bass, Troy Van Leeuwen on guitar, and Tim Alexander on drums. Alexander, however, only performed a handful of live shows and appeared on one song on the group's debut album before being replaced by Josh Freese. Band collaborator and producer Danny Lohner and bassist Jeordie White were also members for a short period in the early 2000s. The band's current lineup features Smashing Pumpkins guitarist James Iha, bassist Matt McJunkins, and drummer Jeff Friedl, the latter two also being contributors to the related Puscifer and Ashes Divide projects. Despite the varied cast and numerous lineup changes, the primary roles of creating A Perfect Circle's songs has remained consistent with Howerdel as music composer, and Keenan writing lyrics and vocal melodies. The band's studio albums have been generally well received critically and commercially, with their first three studio albums selling 4 million copies collectively as of 2005.