A Perfect Circle is an American rock supergroup formed in 1999 by guitarist Billy Howerdel and Tool vocalist Maynard James Keenan. Having met Maynard James Keenan in 1992 while working as a guitar technician for Tool, Howerdel invited him to collaborate.

The original incarnation of the band also included Paz Lenchantin (Pixies) on bass, Troy Van Leeuwen (Failure) on guitar, and Tim Alexander (Primus) on drums. Josh Freese was the primary drummer after the band’s initial round of touring prior to their first album.

The latest lineup features Puscifer and Ashes Divide bassist Matt McJunkins, and Puscifer, Ashes Divide touring drummer, Jeff Friedl, and Smashing Pumpkins rhythm guitarist James Iha. Despite having a varied cast since inception, the stylistic content of the songs has remained consistent with Howerdel as composer, and Keenan penning the lyrics and melodies.