Marjorie Gwendolen Thomas (5 June 1923 – 12 September 2008) was an English opera and oratorio singer for almost three decades. Thomas sang at the Royal Opera House and was a regular performer at the Promenade Concerts and the Three Choirs Festivals and, for many years, a professor of singing at London's Royal Academy of Music. A favourite soloist of Sir Malcolm Sargent's, she also participated in a number of recordings of Gilbert and Sullivan operas.