Margaret Dumont (October 20, 1882 - March 6, 1965) was an American comedic actress.

She is remembered mostly for being the comic foil to Groucho Marx in seven of the Marx Brothers movies. Groucho called her "practically the fifth Marx brother." (In fact, there were five Marx brothers, but only a maximum of four ever performed together.)

Margaret Dumont would probably consider it a tragedy that she is best-known for her performances as the ultimate straight woman in seven of the Marx Brothers' films (including most of their best). By all accounts she never understood their jokes (offscreen and on), which is of course a major reason why she's so funny. Apart from a small role in a 1917 Dickens adaptation, she spent her early career on the stage, ending up with the Marxes in the late 1920s in the stage versions of Cocoanuts, The (1929) and Animal Crackers (1930), and was given a Paramount contract at the same time they were. She played similar roles alongside other great comedians, including W.C. Fields, Laurel & Hardy and Jack Benny and also played straight dramatic parts (her chief love), but few of them made much impact - it is as Groucho Marx's foil that she ranks among the immortals, and she died shortly after being reunited with him on "Hollywood Palace, The" (1964).