He was born Robert Ozell Mosely in Bakersfield, California. He attended Bakersfield Junior College for two years and then worked briefly as a telephone lineman before joining the United States Coast Guard in 1942. In 1944, while visiting Hollywood on leave from the Coast Guard, his boyish good looks were spotted by a talent scout from David O. Selznick's office and he was immediately cast in a bit part in Selznick's Since You Went Away. Following the film's release in 1944, the studio received thousands of letters from fans wanting to know more about him.

He was signed by RKO Pictures in 1946 and began appearing in romantic comedies and dramas but his wooden acting style hurt his chances of advancing in films. In 1951, television came to the rescue of his fleeting career when he was cast in The Adventures of Wild Bill Hickok, which ran for six years.

Following his television series, he appeared in several more films, mostly westerns, before leaving for Europe, where he found greater success in spaghetti westerns.

He was married to actresses Gail Russell (1949-1954) and Sheilia Connolly (1961-1963). Both marriages ended in divorce. He has four children - three daughters and one son.

Guy Madison died in 1996 and was buried in the Palm Springs Mortuary & Mausoleum in Palm Springs, California.