Mary Eaton (January 29, 1901 – October 10, 1948) was an American stage actress, singer, and dancer in the 1910s and 1920s, probably best known today from her appearance in the first Marx Brothers film, The Cocoanuts (1929). A professional performer since childhood, she enjoyed success in stage productions such as the Ziegfeld Follies. She appeared in another early sound film, Glorifying the American Girl (1929). Her career declined sharply during the 1930s.