Billy Budd, Op. 50, is an opera by Benjamin Britten to a libretto by the English novelist E. M. Forster and Eric Crozier, based on the short novel Billy Budd by Herman Melville. It was first performed at the Royal Opera House, London, on 1 December 1951 in four acts, but it was later revised as a two-act opera with a prologue and an epilogue.

The author E. M. Forster had an interest in the novella, which he discussed in his Clark lectures at Cambridge University. Meeting Britten before the Second World War, he developed a friendship with the composer. In 1948, they discussed whether Forster would write a libretto for Britten, and by that November, Britten seems to have mentioned Billy Budd as a possible work to be adapted. Forster agreed to this project, and worked with Eric Crozier, a regular Britten collaborator, to write the opera's libretto.

While Britten was composing the music, the Italian composer Giorgio Federico Ghedini premiered his one-act operatic setting of Billy Budd at the 1949 Venice International Festival. This disturbed Britten, but Ghedini's opera gained little notice.

Britten originally intended the title role for Geraint Evans, who prepared it but then withdrew because it lay too high for his voice. Britten chose Theodor Uppman to replace him, and Evans sang a different role, that of Mr Flint. When Britten conducted the premiere, the work received 17 curtain calls. Uppman was acclaimed as a new star.