Princess Ida; or, Castle Adamant is a comic opera with music by Arthur Sullivan and libretto by W. S. Gilbert. It was their eighth operatic collaboration of fourteen. Princess Ida opened at the Savoy Theatre on 5 January 1884, for a run of 246 performances. The piece concerns a princess who founds a women's university and teaches that women are superior to men and should rule in their stead. The prince to whom she had been married in infancy sneaks into the university, together with two friends, with the aim of collecting his bride. They disguise themselves as women students, but are discovered, and all soon face a literal war between the sexes.

Sir Arthur Seymour Sullivan was an English composer. He is best known for 14 operatic collaborations with the dramatist W. S. Gilbert, including H.M.S. Pinafore, The Pirates of Penzance and The Mikado. His works include 24 operas, 11 major orchestral works, ten choral works and oratorios, two ballets, incidental music to several plays, and numerous church pieces, songs, and piano and chamber pieces. His hymns and songs include "Onward, Christian Soldiers" and "The Lost Chord".