Erwin Ratz (22 December 1898, Graz – 12 December 1973, Vienna) was an Austrian musicologist and music theorist. He is known especially for his work as president of the Gustav Mahler Gesellschaft and for his book Einführung in die musikalische Formenlehre. During Nazi rule, he saved the lives of several Austrian Jews by sheltering them in his apartment for a number of years.