Keir Atwood Dullea (pronounced 'Keer Du-Lay') was born on May 30, 1936, in Cleveland, Ohio, USA. He made a name for himself in the cinematic world for his portrayal of astronaut David Bowman in the 1968 iconic film 2001: A Space Odyssey and its 1984 sequel, 2010: The Year We Make Contact. His acting career also includes other noteworthy films like David and Lisa (1962), Bunny Lake Is Missing (1965), and Black Christmas (1974). Despite gaining recognition for his work in films, Dullea expressed a preference for the stage. An active performer in New York City and regional theaters, his early life was devoted to pursuing an acting career. He studied acting at the Neighborhood Playhouse School of the Theatre in New York City. His journey in the world of acting began with a television adaptation of Mrs. Miniver (1960) with Maureen O'Hara, where he played the German pilot.

Dullea made several guest appearances on popular television shows such as Route 66, The New Breed, Checkmate and Cain's Hundred. His first significant film role was in 1961's Hoodlum Priest. His performance was so well-received that he was offered long-term contracts by major production houses such as Metro-Goldwyn-Mayer and Disney, which he turned down. In 1962, he starred in David and Lisa, a low-budget film that turned out to be a breakout hit. His portrayal of troubled youths won him recognition and he was voted 'find of the year' by Film Daily. Over the course of his career, Dullea has demonstrated versatility, performing in a range of roles to avoid being typecast. He appeared as a US Senator in Robert De Niro's film The Good Shepherd (2006) and even did voiceover work for CBS Radio Mystery Theater which ran from 1974 to 1982. His most recent work includes the role of Fleet Admiral Terrence Hood in the Paramount+ TV series Halo, which premiered in March 2022.