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.