King Arthur, subtitled "The British Worthy", is an opera in five acts, with a libretto by John Dryden and music by Henry Purcell. The opera was first performed at the Queen's Theatre, Dorset Garden, London, in early summer of 1691. The plot is based on King Arthur's battles between the Saxons and the Britons, rather than the legends of Camelot (although Merlin does make an appearance).