The Pirates of Penzance, premiered in 1879, confirmed the comic genius of librettist W.S. Gilbert and composer Arthur Sullivan, following on the heels of their wildly successful H.M.S. Pinafore . Pirates invade the rocky coast of Cornwall in this topsy-turvy tale of love and duty, highlighted by the famous strains of "Poor Wandering One," "I Am the Very Model of a Modern Major-General," "Oh, Is There Not One Maiden Breast" and "With Cat-Like Tread, Upon Our Prey We Steal." This vocal score includes the complete music and all dialogue, a plot synopsis, articles on the famous partnership and the history of The Pirates of Penzance, a filmography and a discography.

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

The story concerns Frederic, who, having completed his 21st year, is released from his apprenticeship to a band of tender-hearted pirates. He meets the daughters of Major-General Stanley, including Mabel, and the two young people fall instantly in love. Frederic soon learns, however, that he was born on the 29th of February, and so, technically, he has a birthday only once each leap year. His indenture specifies that he remain apprenticed to the pirates until his "twenty-first birthday", meaning that he must serve for another 63 years. Bound by his own sense of duty, Frederic's only solace is that Mabel agrees to wait for him faithfully.

Pirates was the fifth Gilbert and Sullivan collaboration and introduced the much-parodied "Major-General's Song". The opera was performed for over a century by the D'Oyly Carte Opera Company in Britain and by many other opera companies and repertory companies worldwide. Modernized productions include Joseph Papp's 1981 Broadway production, which ran for 787 performances, winning the Tony Award for Best Revival and the Drama Desk Award for Outstanding Musical, and spawning many imitations and a 1983 film adaptation. Pirates remains popular today, taking its place along with The Mikado and H.M.S. Pinafore as one of the most frequently played Gilbert and Sullivan operas.