H.M.S. Pinafore
H.M.S. Pinafore, or The Lass That Loved a Sailor  is a two-act operetta by Gilbert and Sullivan. It is the fourth of their fourteen operettas. It premiered on 25 May 1878 at the Opera Comique in London, England. It had 571 performances. The operetta became an international success, and had great influence on the development of musical theatre in Britain and America.