Thomas Stewart (August 29, 1928 – September 24, 2006) was an American bass-baritone who sang an unusually wide range of roles, earning global acclaim particularly for his performances in Wagner's operas.

A regular at the Bayreuth Festival for 13 years (1960–72), Stewart sang most of Wagner's heroic baritone roles, including Wotan/Wanderer and Gunther in the Ring Cycle, the Dutchman, Wolfram in Tannhäuser, and Amfortas in Parsifal.

Over the next decade he figured in many stage and broadcast performances as the Met's leading Wagner baritone (Wotan/Wanderer, Hans Sachs in Die Meistersinger, Kurwenal in Tristan und Isolde, Amfortas, Wolfram, the Dutchman, Gunther).

He also sang a variety of other roles: Golaud, Jochanaan in Salome, Orest in Elektra, Iago in Verdi's Otello, Balstrode in Peter Grimes, the four villains in Contes d'Hoffmann, as well as Mozart's Almaviva and Don Giovanni.

In his prime years Stewart also returned to Lyric Opera of Chicago to sing the Dutchman and Hans Sachs, as well as Orest, Ford, and Mozart's Almaviva.