Sir William Schwenck Gilbert (18 November 1836 - 29 May 1911) was an English dramatist, librettist, poet and illustrator best known for his fourteen comic operas produced in collaboration with the composer Sir Arthur Sullivan, of which the most famous include H.M.S. Pinafore, The Pirates of Penzance, and one of the most frequently performed works in the history of musical theater, The Mikado.