He was born Peter Seamus O'Toole in County Galway, Ireland, but was raised in Leeds, England. His early childhood in Ireland was difficult. Patrick O’Toole, like his son Peter as an adult, was a tall, slim, dashing rascal who was unlucky at the racetrack, nearly always drank too much, & fought with the police.

‘When my father would come home from the track after a good day, the whole room would light up—it was fairyland—but when he lost, it was black, it was always either a wake or a wedding.’

He left school at an early age and became a journalist, working at the Yorkshire Evening News. But after two years National Service in the Royal Navy he studied (on a scholarship) at the prestigious Royal Academy of Dramatic Art, where his classmates included Albert Finney, Alan Bates, Richard Harris, and Derek Jacobi. He worked in theatre, gaining recognition as a Shakespearean actor at the Bristol Old Vic and with the English Stage Company, before making his television debut in 1954 and a very minor film debut in 1959. In 1958 he married actress Siân Phillips.

In 1960, director David Lean was struggling to find a leading man for his upcoming ‘Lawrence of Arabia’, after Albert Finney & Marlon Brando had turned him down. Lean once recalled,
‘So I used to spend my days in cinemas in the West End, & one day I went to a film called ‘The day they robbed the bank of England’, & there was Peter O'Toole, playing a sort of silly-ass Englishman in a trout fishing scene’

Lean subsequently stood up to his studio & producers & insisted on O'Toole as the desert dreamer, even though a pint of Scotch had tellingly dropped out of the actor's suit jacket during his audition. So started an epic that was to shape O’Tooles career from thence forward. Lawrence of Arabia recounts the larger-than-life exploits of T.E. Lawrence (Peter O'Toole), an Officer in the British army serving in the Middle East during World War I, who, according to one observer, "was a poet, a scholar, and a mighty warrior.

Peter was a hell raiser and eventually the boozing & cavorting took a terrible toll, however. O’Toole’s legendary overindulgence led to near-fatal hemorrhaging & the removal of part of his stomach & intestines. His daughters Kate & Pat (both of whom later became actresses) cared for him during his long convalescence. In 1977, his 44-year-old, highly talented Welsh actress wife Sian Phillips, (best known for her fabulous turn as evil empress Livia in PBS’s I CLAUDIUS) left him to marry a 26-year-old. Asked whether he had regrets about nearly losing his license for speeding in life’s fast lane, O’Toole reflected,

‘Only French singers don’t have regrets’.

Severe illness related to his heavy drinking almost ended his life in the late 1970s, but he recovered and returned to work, although he found it harder to get in films, resulting in more work for television and occasional stage roles. He survived by giving up alcohol and, after serious medical treatment, returned to films with triumphant performances in The Stunt Man (1980) and My Favorite Year (1982).