She'll accept her Oscar at the film academy's Governors Awards ceremony Saturday night. Other honorees include Hayao Miyazaki, Jean-Claude Carriere and Harry Belafonte.
The legendary redhead said she cried when she first heard the news, and can't seem to stop.
"It's just absolutely wonderful," she said. "I keep thinking, 'Oh, this is a league of baloney. They're not telling me the truth.'"
The legendary beauty has made more than 60 films since her big-screen debut in 1938, including John Ford's 1941 best picture winner, How Green Was My Valley. She starred in several John Wayne films, including Rio Grande, The Wings of Eagles, and a self-proclaimed favorite, The Quiet Man. She's also known for her roles in the original Miracle on 34th Street and Sentimental Journey.
"Making movies is a wonderful experience," she said. "It's wonderful the stories that you fall in love with and you make and they wind up being very successful, and it breaks your heart almost. I don't mean with sadness. It breaks your heart with joy."
— Independent.ie (@Independent_ie) September 2, 2014
O'Hara admitted that she did do it for the money.
"As kids — and anybody who says they don't love this, they're fibbers — we loved making the money," she said.
The Irish actress is preparing for the big night, wondering how and who to thank when she receives her Oscar.
"It's hard to know how you're going to say thank you to all the people you should say thank you to," she said, "so it's going to be very difficult."
She said she already has a place picked out in her home for her well-deserved trophy — on the mantel of her fireplace "high enough so one of the kids can't knock it down!"
Highlights from Saturday's dinner ceremony will be included in the 2015 Academy Awards telecast in February.