The Pirates of Penzance, or The Slave of Duty, is a comic opera in two acts, with music by Arthur Sullivan an libretto by W. S. Gilbert. It is one of the Savoy Operas. The opera's official premiere was at the Fifth Avenue Theatre in New York City on December 31, 1879, where the show was a hit with audiences and critics. The London premiere was on April 3, 1880, at the Opera Comique, where it ran for 363 performances, having already been playing successfully for over three months in New York.