At 14, joined Ireland's National Theatre, Abbey Theatre.
Was discovered by actor Charles Laughton after a screen test.
Acted alongside John Wayne in five movies: Rio Grande (1950), The Quiet Man (1952), The Wings of Eagles (1957), McLintock! (1963) and Big Jake (1971).
John Ford directed her in five movies: How Green Was My Valley (1941), Rio Grande (1950), The Quiet Man (1952), The Long Gray Line (1955) and The Wings of Eagles (1957).
Successfully sued tabloid magazine Confidential in 1957 over a story that she was seen necking in the back of a theater. She was out of the country at the time the incident supposedly took place, and showed her passport as proof.
Her third husband was the first pilot to fly a passenger plane nonstop from Ireland to New York. When he died years later in a plane crash, O'Hara became CEO of his St. Croix-based airline.