Princess Ida, or Castle Adamant, is a comic opera with music by Arthur Sullivan and libretto by W. S. Gilbert. It opened at the Savoy Theatre on January 5, 1884, for a run of 246 performances. By Savoy Opera standards, it was not considered a success (a particularly hot summer in London did not help ticket sales), and it was not revived in London until 1919. This was the eighth operatic collaboration of fourteen between Gilbert and Sullivan.