Boyd was born William Millar. A rugged, virile, handsome Irish star, he began appearing on the British, Canadian, and American stage in childhood, as well as doing some work on radio. After five years looking for film work in the U.S., he landed a role in the British-made An Alligator Named Daisy (1955), his first big break. His greatest success was as Massala in MGM's spectacle Ben-Hur, after which he tended to appear in epics and historical films. His career wilted, however, and he ended up making TV movies and low-budget European films before dying of a heart attack at age 48.