Marion O'Brien is an Australian Paralympic table tennis player and athlete. At the 1964 Tokyo Games, she won a gold medal in the women's doubles C event with Daphne Ceeney, a silver medal in the women's javelin C event, and a bronze medal in the women's singles C event. At the 1968 Tel Aviv Games, she won a silver medal in the women's doubles C event with Elaine Schreiber, and a bronze medal in the women's slalom C event.