Billy Budd is a short novel written around 1891 by Herman Melville.

The work has been central to Melville scholarship since it was discovered in manuscript among Melville's papers in a barn in 1924 and has an ignominious editorial history, as poor transcription and misinterpretation of Melville's notes on the manuscript marred the first published editions of the text. For example, early versions gave the book's title as "Billy Budd, Foretopman," while it now seems clear that Melville intended "Billy Budd, Sailor"; some versions wrongly included a chapter that Melville had excised as a preface (the correct text has no preface); some versions fail to correct the name of the ship to Bellipotent from the Indomitable, as Melville called the boat in an earlier draft. In 1962, Harrison Hayford and Merton M. Sealts, Jr., established what is now considered the correct text; it was published by the University of Chicago Press, and most editions printed since then follow the Hayford/Sealts text.

A story ultimately about good and evil, Billy Budd has often been interpreted allegorically, with Billy interpreted typologically as Christ or the Biblical Adam, with Claggart (compared to a snake several times in the text) figured as Satan. Vere is often associated with God the Father. Some critics, notably Eve Kosofsky Sedgwick, have argued that the text treats important homoerotic tensions. Other critics have conceptualized Billy Budd as a historical novel that attempts to evaluate man's relation to the past.

The plot follows Billy Budd, a seaman pressed into service aboard the HMS Bellipotent in the year 1797, when the British Navy was following reeling from two major mutinies and was threatened by Napoleon's military ambitions. Billy, suffused with innocence, openness, and natural charisma, is adored by the crew, but for unexplainable reasons arouses the antagonism of the ship's Master-at-Arms, John Claggart, who falsely accuses Billy of conspiracy to mutiny. Brought before the Captain Edward Fairfax "Starry" Vere to answer to the charges, Billy is unable to find the words to respond, and lashes out seemingly involuntarily at Claggart, killing him with a single blow. Vere, an eminently thoughtful man whose name recalls the Latin words "veritas" (truth) and "vir" (man), is convinced of Billy's innocence before God but insists on following the letter of the Mutiny Act and sentencing Billy to death, arguing that any appearance of weakness in the officers and failure to enforce discipline could stir the already-turbulent waters of mutiny throughout the British fleet. Condemned to be hanged from the ship's yardarm at dawn the morning after the killing, Billy's final words are, "God bless Captain Vere!"

Benjamin Britten wrote an opera, also called Billy Budd, based on Melville's novel. It was first performed in 1951.

Peter Ustinov produced, directed, and co-wrote a film version of Billy Budd, released in 1962. It starred Terence Stamp as Billy Budd, Robert Ryan as John Claggart, and Peter Ustinov as Captain Vere. Stamp was nominated for an Academy Award for Best Supporting Actor.

Billy Budd is also the name of a song by Steven Morrissey, on the album Vauxhall and I, as a disguised jab against his former friend and Smiths guitarist, Johnny Marr.