Mischa Anne Marsden Barton ( born 24 January , 1986 , London ) is an award-winning English-American actress best known for her role as Marissa Cooper in the American television series The O.C. Mischa Anne Marsden Barton ( born 24 January 1986 ) is an English-American fashion model , film , television , and stage actress , best known for her role as Marissa Cooper in the American television series The O.C. .