Erwin Ratz (1898 - 1973) was an Austrian musicologist and music theorist. He studied musicology with Guido Adler and composition with Arnold Schoenberg and was active in the Schoenberg circle. In the 1920s he worked at the Bauhaus. After World War II he was a professor of musical form and analysis in Vienna. He is best known for his work Einführung in die musikalische Formenlehre ("Introduction to Musical Form"), which is devoted primarily to the work of Bach and Beethoven, and for his role in editing Mahler's works.