Barry Guy (born 1947 in London) is a British composer and double bass player. His range of interests encompasses early music, contemporary composition, jazz and improvisation, and he has worked with a wide variety of orchestras in the UK and Europe. He also taught at Guildhall School of Music.

Guy came to the fore as an improvising bassist as a member of a trio with pianist Howard Riley and drummer Tony Oxley. He also became an occasional member of John Stevens' ensembles in the 1960s and 1970s, including the Spontaneous Music Ensemble. In the early 1970s, he was a member of the influential free improvisation group Iskra 1903 with Derek Bailey and trombonist Paul Rutherford (a project later revived in the 1990s, with violinist Phil Wachsmann replacing Bailey). He also formed a long-standing partnership with saxophonist Evan Parker, which led to a trio with drummer Paul Lytton which became one of the best-known and widely-travelled free-improvising groups of the 1980s and 1990s.

Guy's interests in improvisation and formal composition received their grandest form in the London Jazz Composers Orchestra. Originally formed to perform Guy's composition Ode in 1974 (released as a 2-LP set on Incus and later, in expanded form, as a 2-CD set on Intakt), it became one of the great large-scale European improvising ensembles. Early documentation is spotty – the only other recording from its early years is Stringer (FMP^*) – but beginning in the late 1980s the Swiss label Intakt set out to document the band more thoroughly. The result was a series of ambitious, album-length compositions designed to give all the players in the band maximum opportunity for expression while still preserving a rigorous sense of form: Zurich Concerts, Harmos, Double Trouble (originally written for an encounter with Alexander von Schlippenbach's Globe Unity Orchestra, though the eventual CD was just for the LJCO), Theoria (a concerto for guest pianist Irène Schweizer, Three Pieces, and Double Trouble Two. The group disbanded in the mid-1990s, and Guy has since then created a smaller ensemble, the Barry Guy New Orchestra.

He has also written for other improvising ensembles, such as the NOW Orchestra and ROVA (the piece Witch Gong Game inspired by images by the visual artist Alan Davie).

Guy's session work in the pop field includes playing double bass on the song "Nightporter", from the Japan album Gentlemen Take Polaroids.

He is married to the early music violinist Maya Homberger. They now live in Switzerland.

1947 births | 20th century classical composers | 21st century classical composers | Classical double-bassists | English composers | Free improvisation | Living people