Monica Sinclair (23 March 1925 – 7 May 2002) was a British operatic contralto, who sang many roles with the Royal Opera, Covent Garden during the 1950s and 1960s, and appeared on stage and in recordings with Joan Sutherland, Luciano Pavarotti, Maria Callas, Sir Thomas Beecham, Sir Malcolm Sargent, and many others. She had a great gift for comedy, and she recorded many of the Gilbert and Sullivan operas, as well as the standard operatic repertory.