Blanche Thebom (September 19, 1915 – March 23, 2010) was an American operatic mezzo-soprano, voice teacher, and opera director. She was part of the first wave of American opera singers that had highly successful international careers. In her own country she had a long association with the Metropolitan Opera in New York City which lasted 22 years. Opera News stated, "An ambitious beauty with a velvety, even-grained dramatic mezzo, Thebom was a natural for opera: she commanded the stage with the elegantly disciplined hauteur of an old-school diva, relishing the opportunity to play femmes du monde such as Marina in Boris Godunov, Herodias and Dalila."

While Thebom sang a wide repertoire which encompassed everything from Handel and Mozart to Verdi and Debussy, she was best known for her performances in the operas of Richard Wagner. Two Wagner roles with which she was particularly associated were Fricka in Die Walküre and Brangaene in Tristan und Isolde. She notably sang the latter role in the famous 1952 EMI recording made in London with Kirsten Flagstad, Ludwig Suthaus, and conductor Wilhelm Furtwängler. She is Didon in Les Troyens (world premiere 1957, conducted by Rafael Kubelik). In addition to several other recordings, she also appeared in two feature films during her career: Irish Eyes Are Smiling (1944) and The Great Caruso (1951).

After retiring from the stage in 1967, Thebom worked as an opera director in Atlanta for 6 years. She then taught singing both privately and on the music faculties of the University of Arkansas and San Francisco State University. She also co-founded the Opera Arts Training Program of the San Francisco Girls Chorus and served on the board of the Metropolitan Opera for nearly 40 years.