Paul was born on 27th May 1971, in London, England. He is 6'3". Paul lived in North West London until the age of 9, then moved to Hertfordshire (Brookman's Park). He still resides in London. Paul was introduced to acting at a young age (his father is British actor Thane Bettany). He has an older sister, who is a writer.

Paul studied for stage acting at the Drama Centre in London, then made his way onto screens in Britain and shortly thereafter in the U.S. Paul's stage debut was in the West End play "An Inspector Calls". Paul prefers beer and cigarettes to working out. He started smoking when he was 14, after seeing James Dean in "Rebel Without A Cause".

Paul has appeared naked in almost all of his works. Paul's acting heroes are Al Pacino, Humphrey Bogart, Bob DeNiro, Peter O'Toole and Vincent Cassel. Paul is married to actress Jennifer Connelly, and they have a son together, named Stellan.