Sleep is a 1990s stoner rock band from San Jose, California. Al Cisneros, Justin Marler , Chris Haikus and Matt Pike formed the band in the late 1980s and released their debut, Volume One , in 1991 (see 1991 in music). Frequently compared to pioneers like Saint Vitus, Sleep soon gained a devoted fanbase within the developing stoner rock scene.

Holy Mountain (1993) is the band's widely-acknowledged pinnacle and is a seminal stoner and doom metal album. This was followed by a potentially lucrative offer from London Records, and Sleep signed with them. Under this contract, in 1995 they began work on their third album, Dopesmoker . Dopesmoker was actually one single song which was over one hour hour in length. The album was submitted to London Records, who declared that it was unmarketable and therefore could not be released. Sleep returned to the studio and then submitted their second attempt at the new album. They had retitled it Jerusalem, re-written some of the lyrics, and trimmed it down to a lean 52 minutes, but it was essentially the same album and song as Dopesmoker. London Records again refused to release it. Frustrated and generally unhappy with the situation, the members of Sleep decided it was time to disband.

In 1998, Jerusalem was released posthumously as an "official bootleg" by a friend of the group. Sleep and their former manager had full knowledge of this and gave it their approval. In 1999, Jerusalem was given an official legitimate release by The Music Cartel in the US and Rise Above Records in Europe. Finally, in 2003 the original version of Dopesmoker was officially released by Tee Pee Records . It is generally considered the definitive version of the album.

Pike soon formed his own group High on Fire while Marler (now a monk) and Haikus formed The Sabians . In 2004, Cisneros and Hakius reunited as a duo known as Om.