Susan Fleming (February 19, 1908 – December 22, 2002) was an American actress and the wife of comic actor Harpo Marx. Fleming was known as the "Girl with the Million Dollar Legs" for a role she played in the W. C. Fields film Million Dollar Legs (1932). Her big stage break, which led to her Hollywood career, was as a Ziegfeld girl, performing in The Ziegfeld Follies.

Fleming was from New York City and went to school in Forest Hills, Queens. After starring in the Ziegfeld Follies productions on Broadway, she started appearing in movies. One of her earliest film roles was a starring role in Range Feud as Judy Walton, the love interest of John Wayne. Fleming combined her dancing and cinematic interests in the 1932 movie Million Dollar Legs, in which she played the daughter of W. C. Fields' character. As part of a publicity stunt for the film, her legs were insured for the eponymous million dollars.

Fleming was unhappy with Hollywood, stating in a 1995 interview that she found "nothing more boring than working on a movie... I hated it!". At a dinner party held in the home of Samuel Goldwyn, she was seated next to Harpo Marx and found him fascinating. Despite his silent persona in films, she found Marx to be "a warm, fun, darling man to talk to". She pursued him relentlessly, dating for four years and proposing marriage to him on three separate occasions before he accepted. She ended her Hollywood career when she married Marx on September 28, 1936. Fleming's wedding to Marx was revealed to the public when President of the United States Franklin D. Roosevelt sent the couple a telegram of congratulations in November. Marx had sent a thank you letter to Roosevelt in appreciation for a signed photograph of the President, in which Marx had stated that he was "in line for congratulations, too, having been married since September" in an unspecified "little town up North".

Fleming outlived Marx by almost forty years during which she was an artist and activist in the Palm Springs area. She died at age 94 on December 22, 2002, of a heart attack at Eisenhower Medical Center in Rancho Mirage. She was survived by a daughter, three sons, five grandchildren; and two great-grandchildren.