O'Neal was born on April 20, 1941 in Los Angeles, California. He studied at the University High School. O'Neal was married to Joanna Cook Moore from 1963 until they divorced in 1967. Then he was married to Leigh Taylor-Young from 1967 until they divorced in 1973. Then he was married to Farrah Fawcett from 1979 until they divorced in 1997. Then they remarried in 2001 until her death in 2009. He has four children, including Tatum O'Neal. He now lives in Malibu, California.