Margaret Dumont (October 20, 1889 - March 6, 1965) was an American comedic actress.

Born Daisy Juliette Baker in Brooklyn, New York she adopted the stage name Margaret and/or Marguerite Dumont. 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. (There were in fact five Marx brothers, but only a maximum of four ever performed together.)

Dumont played wealthy high-society widows whom Groucho alternately insulted and romanced for their money. They include Mrs Rittenhouse in Animal Crackers, Mrs Claypool in A Night at the Opera, Mrs Gloria Teasdale in Duck Soup, Martha Phelps in The Big Store, Mrs Susan Dewkesbury in At the Circus, and Emily Upjohn in A Day at the Races. Groucho once said a lot of people believed they were married in real life, but they were not.

Over the course of her lifetime she played in 40 movies, not including some minor silent work. Her first feature film was the Marx Brothers movie The Cocoanuts in 1929 in which she played Mrs Potter, the same role she played in the stage version from which the film was adapted. Her last movie was What a Way to Go! in 1964, in which she played Shirley MacLaine's mother.

She also played the same type with W.C. Fields (in Never Give a Sucker an Even Break), Abbott and Costello, Laurel and Hardy, Jack Benny and Danny Kaye. She also played some dramatic parts.

In her interviews and press profiles she preserved the myth of her on-screen character - the rich, regal woman who never quite understood the joke - and claimed she had returned reluctantly to acting as a result of widowhood. But as a young actress she had specialised in straight female-leads in musical comedies, where the cardinal rule was to make space for the featured comedian. Perhaps the joke was not entirely on her.

On her passing in 1965, Margaret Dumont was cremated, her ashes stored in the vault at the Chapel of the Pines Crematory in Los Angeles.