An electronica band consisting of the duo of singer Karl Hyde and synthesist Rick Smith, with other members at various points in the band's history. (As of December 2011, DJ Darren Price is a part-time third member of the band.) Hyde and Smith first worked together in the early 1980s in a synth pop band called Freur, which released two albums. In 1987, the duo formed a band which is now referred to by fans as "Underworld Mark I", which played a mismash of '80s styles; this band released two albums before disbanding in 1990. At this point, Hyde and Smith teamed with DJ Darren Emerson and turned their attentions towards electronica, particularly techno and trance styles.

Underworld achieved widespread noteriety when a mix of their track "Born Slippy" was used in the film Trainspotting in 1996. This made a hit out of Underworld Mark II's album, Second Toughest in the Infants, and the tracks "Junita/Kiteless" and "Pearl's Girl" became hits in the clubs and on the then-new XM Radio's "The System" channel. After the next album, "Beaucoup Fish", Emerson left the band and Hyde and Smith continued as a duo. Since then, the band has released three additional albums and numerous Internet-only tracks and remixes.

Underworld is noted for the amount of sung-live and played-live, as opposed to sampled and looped, parts in their tracks. They retain traces of the '80s synth-pop sound in which Hyde and Smith got their start, although with a large dose of electronica sensibility. They are noted for fusing tracks and their titles, resulting in titles combined with slashes such as "Rez/Cowgirl" and "Banstyle/Sappy's Curry" (the latter of which is a downtempo track which features Hyde on accoustic guitar).