Marissa Cooper is a fictional character from the television series The O.C., which aired from 2003 to 2007. Portrayed by actress Mischa Barton, Marissa is a wealthy teenager living in the upscale community of Newport Beach, California. She is known for her complex personality, struggles with family issues, and tumultuous relationships. Throughout the series, Marissa experiences various challenges, including friendship dynamics and romantic entanglements, particularly with characters like Ryan Atwood and Seth Cohen. Her character arc explores themes of love, loss, and personal growth, making her a central figure in the show's narrative.