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