Tool is a rock band from Los Angeles known for introducing dark, vaguely underground metal to rock music. Formed in 1990, the group's line-up includes drummer Danny Carey, guitarist Adam Jones, and vocalist Maynard James Keenan.

Justin Chancellor has been the band's bassist since 1995, replacing their original bassist Paul D'Amour. Tool has won three Grammy Awards, performed worldwide tours, and produced albums topping the charts in several countries.

Tool emerged with a heavy metal sound on their first studio album, Undertow (1993), and became a dominant act in the alternative metal movement with the release of their follow-up album Ænima in 1996.

Their efforts to unify musical experimentation, visual arts, and a message of personal evolution continued with Lateralus (2001) and 10,000 Days (2006), gaining critical acclaim and international commercial success.

Their fifth studio album, Fear Inoculum, their first in thirteen years, was released on August 30, 2019, to widespread critical acclaim. Prior to its release, the band had sold over 13 million albums in the US alone.

Fear Inoculum was nominated for the Grammy Award for Best Metal Performance at the 62nd Grammy Awards. Due to Tool's incorporation of visual arts and very long and complex releases, the band is generally described as a style-transcending act and part of progressive rock, psychedelic rock, and art-rock.

The relationship between the band and today's music industry is ambivalent, at times marked by censorship, and the band's insistence on privacy.