Tortoise is an American post-rock band formed in Chicago, Illinois, in 1990.
Tortoise's almost entirely instrumental music defies easy categorization, and the group gained significant attention from their early career. The members have roots in Chicago's fertile music scene, playing in various indie rock and punk groups. Tortoise was among the first American indie rock bands to incorporate styles closer to Krautrock, dub, minimalism, electronica and various jazz styles, rather than the standard rock and roll and punk that had dominated indie rock for years.
Some have cited Tortoise as being one of the prime forces behind the development and popularity of the post-rock movement. Others, however, have characterised Tortoise's music as being heavily indebted to progressive rock.
Other groups related to Tortoise include The Sea and Cake, Brokeback, Slint, Isotope 217, Chicago Odense Ensemble and the Chicago Underground Duo. Tortoise records on the Thrill Jockey label.