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.