Born to a Catholic family in Liverpool, he worked as an insurance assessor before going into the theatre as a career. His first film appearance was in 1962, and he subsequently appeared frequently on television (notably in Elizabeth R), and in British films such as Educating Rita (1983) and Henry V (1989).
He married Judi Dench in 1971, and they had one daughter. Both devout Christians (though from different denominations), theirs was one of the most successful showbiz marriages, and they worked together on several series of the sitcom, A Fine Romance, from 1981 onwards. Shortly before his death from lung cancer, Williams was awarded a papal knighthood.