Marthe Keller is a Swiss actress. She is perhaps best known for her role in the film Marathon Man (1976), for which she was nominated for a Golden Globe Award.

Marathon Man is a 1976 American thriller film directed by John Schlesinger. It was adapted by William Goldman from his 1974 novel of the same title and stars Dustin Hoffman, Laurence Olivier, Roy Scheider, William Devane and Marthe Keller. In the film, "Babe" Levy, a graduate student, becomes embroiled in a plot by Nazi war criminal Christian Szell to retrieve ill-gotten diamonds from a safe deposit box owned by Szell's dead brother. Babe becomes unwittingly involved due to his brother Doc's dealings with Szell.