Susanne Mentzer (born January 21, 1957) is an American operatic mezzo-soprano. She is best known for singing trouser roles, such as Cherubino in Mozart's Le nozze di Figaro, Idamante in Mozart's Idomeneo, Octavian in Richard Strauss' Der Rosenkavalier and the composer in Strauss' Ariadne auf Naxos, as well as other music of Mozart, Strauss, Rossini, Berlioz and Mahler.
She created the role of the mother of Yueyang in Tan Dun's opera The First Emperor at the Metropolitan Opera on December 21, 2006. She has also premiered works by Libby Larsen, Daniel Brewbaker and Carlisle Floyd.