During the years when the Gilbert and Sullivan ("G&S") operas were being written, Richard D'Oyly Carte produced operas by other composer–librettist teams, either as curtain raisers to the G&S pieces, or to fill the theatre when no G&S piece was available. To their contemporaries, the term "Savoy Opera" referred to any opera that appeared at that theatre, regardless of who wrote it.
Aside from curtain raisers (which are listed in the second table below), the G&S operas were the only works produced at the Savoy Theatre from the date it opened (10 October 1881) until The Gondoliers closed on 20 June 1891. Over the next decade, there were only two new G&S pieces (Utopia Limited and The Grand Duke), both of which had comparatively brief runs. To fill the gap, Carte mounted G&S revivals, Sullivan operas with different librettists, and works by other composer–librettist teams. Richard D'Oyly Carte died on 3 April 1901. If the nexus of Carte and the Savoy Theatre is used to define "Savoy Opera," then the last new Savoy Opera was The Rose of Persia (music by Sullivan, libretto by Basil Hood), which ran from 28 November 1899 – 28 June 1900.
Gilbert, Workman and German at a rehearsal
After Carte's death, his wife Helen Carte assumed management of the theatre. She continued to produce new pieces in the G&S style, along with G&S revivals. Counting the pieces that Mrs. D'Oyly Carte and the D'Oyly Carte Opera Company produced, the last Savoy Opera was A Princess of Kensington (music by Edward German, libretto by Basil Hood), which ran for four months in early 1903. This is the point that Cyril Rollins and R. John Witts adopt as the end of the Savoy Operas. After A Princess of Kensington, Mrs. D'Oyly Carte relinquished control of the theatre until 8 December 1906, when she produced two seasons of G&S revivals in repertory, with Gilbert returning to direct.
In March 1909, Charles H. Workman assumed control of the theatre, producing three new pieces, including one by Gilbert himself, Fallen Fairies (music by Edward German). The last of these Workman-produced works came in early 1910, Two Merry Monarchs, by Arthur Anderson, George Levy, and Hartley Carrick, with music by Orlando Morgan. The contemporary press referred to these works as "Savoy Operas", and S. J. Adair Fitz-Gerald regarded Workman's pieces as the last Savoy Operas.
Fitz-Gerald wrote his book, The Story of the Savoy Opera, in 1924, when these other pieces were still within living memory. But over time, all of the works produced at the Savoy by composers and librettists other than Gilbert and Sullivan were largely forgotten. The term "Savoy Opera" came to be synonymous with the thirteen extant works of Gilbert and Sullivan. The first collaboration of Gilbert and Sullivan – the 1871 opera Thespis – was not a Savoy Opera under any of the definitions mentioned to this point, as Richard D'Oyly Carte did not produce it, nor was it ever performed at the Savoy Theatre. Given its lack of a D'Oyly Carte or Savoy connection, Thespis has a tenuous claim to be a "Savoy Opera." However, Rollins & Witts include it in their compendium of the Savoy Operas, as does Geoffrey Smith. The Oxford English Dictionary defines the phrase as: "Designating any of the Gilbert and Sullivan operas originally presented at the Savoy Theatre in London by the D'Oyly Carte company. Also used more generally to designate any of the Gilbert and Sullivan operas, including those first presented before the Savoy Theatre opened in 1881, or to designate any comic opera of a similar style which appeared at the theatre".