Flaccus is a composer from the second century BC, of whom little is known. He was a slave of one of Terence's patrons and wrote musical scores for Terence's comedies (playing or composing music was no occupation for a free citizen).

Flaccus has the distinction of being the only composer of Ancient Rome of whom any music remains. A musical phrase accompanying a single line of Terence's play Hecyra was copied in the eighteenth century by Italian composer Arcangelo Corelli from an ancient manuscript that now is lost.