'''''Amadis''''' is an opera in three acts with prologue by Jules Massenet to a French libretto by Jules Claretie based on the Spanish knight-errantry romance ''Amadis de Gaula'', originally of Portuguese origin, by Garci Rodríguez de Montalvo.
It was first performed at the Opéra de Monte-Carlo on 1 April 1922, nearly ten years after Massenet's death. Massenet had started to compose the piece in 1895 but shelved it and completed it clandestinely in the last years of his life. ''Amadis'' is one of three operas by Massenet to have been premiered posthumously; the others are ''Panurge'' (1913) and ''Cléopâtre'' (1914).
''Amadis'' has gained no lasting popularity but was revived (and recorded on the Koch Swann label) during the Massenet Festival in Saint-Étienne, France in 1988.