What was the first Gilbert and Sullivan opera?

Gilbert and Sullivan's first major hit was Trial by Jury (1875). Impresario Richard D'Oyly Carte was then managing the Royalty Theatre. He needed a one-act work to serve as an afterpiece for Offenbach's popular but short La Périchole. Gilbert had already written such a short piece on commission from producer-composer Carl Rosa, whose wife's unexpected death had left the libretto an orphan. Carte suggested that it be set to music by Sullivan. Sullivan was delighted with it, and the piece was produced within a matter of weeks. Trial by Jury, with Sullivan's brother, Fred, as the Learned Judge, was added to the bill with La Périchole and proved itself even more popular than Offenbach's opera, running for 131 performances.