Osborne was born December 12, 1929, in London, England. His childhood was marked by personal poor health and poverty, the latter a condition that worsened after his father's death in 1941. Osborne attended day schools as well as St. Michael's College until he was about eighteen, but that was the extent of his formal education.

Osborne briefly worked in journalism but soon drifted into the theater by accepting a job as a tutor for child actors who were touring with a company. While a failure as a tutor, Osborne did well at his next job with the theater company: assistant stage manager. He eventually began acting, making his on-stage debut in Sheffield in 1948.

Osborne's first play was The Devil Inside Him, produced in 1950, which he wrote with his friend and mentor, Stella Lindon. Over the next few years, Osborne wrote several more plays, none of them successful. In 1956—the...