Princess Toto is a three-act comic opera by W. S. Gilbert and his long-time collaborator Frederic Clay. It opened on 24 June 1876 at the Theatre Royal, Nottingham, starring Kate Santley, W. S. Penley and J. H. Ryley. It transferred to the Royal Strand Theatre in London on 2 October 1876 for a run of only 48 performances. Brief New York and Boston runs followed in 1879–80 starring Leonora Braham and Ryley, and there were later tours in the US. Princess Toto was revived in 1881 at the Opera Comique in London for a run of 65 performances (starring Richard Temple). There was also an 1886 revival in Australia.
Princess Toto was the last work in a long and successful partnership with Clay that had produced four of Gilbert's major musical works up to that date. The year before, Gilbert and Arthur Sullivan, Clay's friend, had premiered their hit Trial by Jury, and after Princess Toto, Gilbert would not collaborate on any further operas with anyone other than Sullivan for the next 15 years.
Despite Clay's tuneful score and Gilbert's amusing libretto, the piece was not a major success, although it did enjoy the various tours and revivals over the years. After the initial production at Nottingham and the subsequent provincial tour, Gilbert sold the performing rights to Clay for a period of ten years. Therefore, it was Clay who oversaw the London productions of 1876 and 1881, and also the New York production and American tours during 1879–80 and later. The theatrical newspaper The Era gave a positive review of the New York production.
The most recent professional production that has been traced was staged by the Birmingham Repertory Company in 1935. A number of amateur companies have staged the piece since the early 1990s.
The publisher of the music, Cramer & Co., stated that the band parts and original printing plates for both Vocal Score and Libretto were destroyed in the World War II London blitz. However, a copy of the parts survives in Australia.