Mitchum, RobertMitch‧um, Rob‧ert /ˈmɪtʃəm, ˈrɒbət $ ˈrɑːbərt/(1917–97) a US film actor, who played leading parts in many films, especially westerns and films about criminals, from the 1940s onwards. Among his best-known films are The Sundowners, Ryan’s Daughter, and The Big Sleep.