Muriel Costa-Greenspon (December 1, 1937 – December 26, 2005) was an American mezzo-soprano who had a lengthy career at the New York City Opera from 1963 to 1993. She portrayed a gallery of character roles that extended from twentieth-century works by Leonard Bernstein, Benjamin Britten, Carlisle Floyd, Lee Hoiby, Arthur Honegger, Gian Carlo Menotti, and Douglas Moore, to the contralto heroines of Gilbert and Sullivan, and comic scene-stealers by Puccini, Mozart, and Donizetti.