Born to actor parents Ryan O'Neal and Joanna Cook Moore in Los Angeles, California, Tatum made her acting debut at the tender age of 10.
Tatum's first ever movie role, playing Addie Loggins opposite her father in Paper Moon, was also the role that won her a Best Supporting Actress Oscar, making her the youngest person ever to win a competitive Oscar.
She went on to star in movies such as Bad News Bears (with which she broke another record as highest-paid child star in history), and International Velvet, among others.
O'Neal has gone on to have a prolific movie and TV career as an adult, appearing in movies such as Little Darlings and Basquiat, and TV shows including Sex and The City, 8 Simple Rules and Rescue Me.
Last year, Tatum published her memoirs A Paper Life.
Tatum has three children with former husband John McEnroe.
Her brother is actor Griffin O'Neal, her sister-in-law is actress Rebecca De Mornay.