Sweeney Todd, the Demon Barber of Fleet Street: A Musical Thriller is a Tony Award-winning musical with a book by Hugh Wheeler and music and lyrics by Stephen Sondheim. The musical is based on the 19th century fictional character Sweeney Todd, though more specifically, the 1973 play Sweeney Todd, the Demon Barber of Fleet Street by Christopher Bond.

Sweeney Todd opened on Broadway at the Uris Theatre on March 1, 1979 and ran for 557 performances. It was directed by Harold Prince with musical staging by Larry Fuller, and starred Len Cariou as Sweeney Todd and Angela Lansbury as Mrs. Lovett. The musical tells the story of Sweeney Todd, who was previously known as Benjamin Barker, who returns from Australia where he has spent fifteen years on false charges. When he learns from Mrs. Lovett, whose meat pies are the worst in London, that his wife poisoned herself after being raped by Judge Turpin (the man who wrongly imprisoned him), and that his daughter is the ward of the same Judge Turpin, he vows revenge.

A feature film adaptation of Sweeney Todd, jointly produced by Dreamworks and Warner Bros., was released on December 21, 2007. Tim Burton directed from a screenplay by John Logan. It stars Johnny Depp as Todd (Depp received an Oscar nomination and a Golden Globe award for his performance), Helena Bonham Carter as Mrs. Lovett, Alan Rickman as Judge Turpin, Sacha Baron Cohen as Signor Pirelli, Jamie Campbell Bower as Anthony Hope, Laura Michelle Kelly as The Beggar Woman, Jayne Wisener as Johanna, Ed Sanders as Toby, and Timothy Spall as Beadle Bamford.

Sondheim's score is one of his most complex to date, with orchestrations by his long-time collaborator Jonathan Tunick. It relies heavily on counterpoint and rich, angular harmonies. Its compositional style has been compared to those of Maurice Ravel, Sergei Prokofiev, and Bernard Herrmann (who scored Alfred Hitchcock films). Sondheim also quotes the ancient Dies Irae Gregorian chant, both as part of the eponymous ballad that runs throughout the score, later heard in a musical inversion, and in the accompaniment to "Epiphany". He also relies heavily on leitmotif - at least twenty distinct ones can be identified throughout the score. Depending on how and where the show is presented, it is sometimes considered an opera. Sondheim himself has described the piece as a "black operetta." An original Broadway cast recording was released in 1979. It included the Judge's "Johanna" and the tooth-pulling contest from Act I, which had been cut in previews.