Gilbert and Sullivan refers to the Victorian-era theatrical partnership of the librettist W. S. Gilbert and the composer Arthur Sullivan and to the works they jointly created. The two men collaborated on fourteen comic operas between 1871 and 1896, of which H.M.S. Pinafore, The Pirates of Penzance and The Mikado are among the best known.

Gilbert, who wrote the words, created fanciful "topsy-turvy" worlds for these operas where each absurdity is taken to its logical conclusion—fairies rub elbows with British lords, flirting is a capital offence, gondoliers ascend to the monarchy, and pirates emerge as noblemen who have gone astray. Sullivan, six years Gilbert's junior, composed the music, contributing memorable melodies that could convey both humour and pathos. Their operas have enjoyed broad and enduring international success and are still performed frequently throughout the English-speaking world. Gilbert and Sullivan introduced innovations in content and form that directly influenced the development of musical theatre through the 20th century. The operas have also influenced political discourse, literature, film and television and have been widely parodied and pastiched by humorists.