His son Patrick posted, "So this is the toughest thing I’ve ever had to say but here we go. My dad passed away peacefully today, with his loving team by his side supporting him and loving him as he would us."

It's unclear how O'Neal died, but he's had his share of health problems, including a prostate cancer diagnosis in 2012. In 2001, he was diagnosed with chronic leukemia.

O'Neal was not only one of the hottest actors in Hollywood back in the day, but he was a major heartthrob. His credits include "What's Up, Doc?" "Paper Moon," "Barry Lyndon," "A  Bridge Too Far," "The Main Event," and "The Driver."

Ryan was nominated in 1970 for a Best Actor Oscar for "Love Story."

He was famously life partners with Farrah Fawcett from 1979 - 1997, and they reconnected between 2001 and 2009, when she died. Patrick said, "Ryan never bragged, but he has bragging rights in Heaven. Especially when it comes to Farrah. Everyone had the poster, he had the real McCoy. And now they meet again."

BTW ... he shared the big screen in "Paper Moon" with his daughter, Tatum O'Neal.

As for the heartthrob part ... well, he dated a gaggle of beautiful women, including Ursula Andress, Barbra Streisand, Bianca Jagger, Jacqueline Bisset, Joan Collins and Diana Ross.

Ryan is survived by 4 children and 5 grandchildren.