Cathy O’Donnell was born Ann Steely in Siluria, Alabama, in 1923. Her parents split when she was young. She attended Oklahoma City University and studied drama at the American Academy of Dramatic Arts in New York City.
She began her career as a stenographer, saving money to move to Hollywood.
She signed with Samuel Goldwyn and made her film debut in 1945, at the age of 22. She appeared in more than 15 feature films through 1959.
O’Donnell married the screenwriter Robert Wyler, the older brother of director William Wyler.
She died of a cerebral hemorrhage brought on by cancer in Los Angeles, in 1970. O’Donnell was 46 years old.