Sleepytime Gorilla Museum (often abbreviated to SGM) is an American experimental rock band, formed in 1999 in Oakland, California.

Some time during the recording of Grand Opening and Closing (2001), drummer David Shamrock left the band and was replaced by Frank Grau.

During the recording of the follow-up, Of Natural History (2004), Grau left the band and was replaced by new drummer Matthias Bossi, formerly of Skeleton Key.

In January 2006 Sleepytime Gorilla Museum signed to The End Records who re-released their début Grand Opening and Closing with three bonus tracks.

[8] Nils Frykdahl, Dan Rathbun, Michael Iago Mellender, and David Shamrock, along with Drew Wheeler, formed a new band called Free Salamander Exhibit in 2013.

"[12] Official announcements for Of Natural History, In Glorious Times and Grand Opening and Closing vinyl re-issues were made by distributor "Blood Music" in September and October 2015.

The name itself apparently comes from a poem called "Of the Future Hides the Past," written by Museum members Lala Rolo and Ikk Ygg.

Some influences include Henry Cow, Swans, Einstürzende Neubauten, King Crimson, Mayhem, Bauhaus, Art Bears, Igor Stravinsky, Thinking Plague, and Univers Zéro.

"[22] Tony Levin, known for his work with progressive rock pioneers King Crimson and also with Peter Gabriel, stated that he is a "huge fan of" Sleepytime Gorilla Museum and chose the track "Sleep is Wrong", which he calls "very, very powerful" as one of the pieces which most influenced his collaborative project, Stick Men.

Levin also credited Sleepytime Gorilla Museum as doing "things that we never dreamed of doing in Crimson or in any band that I've been in," specifically their "radical" and "organic" shifts in tempo.