Nelson died on April 7 while traveling in Bucks County, Pa., his wife, Nansi Nelson, said Friday. The cause of death was not immediately known, she said.
After graduating from the University of California, Berkeley, in 1941, Nelson was signed to MGM after being spotted by a talent scout. He appeared in a number of films for the studio in 1942, including "Shadow of the Thin Man," "Johnny Eager" and "Dr. Kildare's Victory." He also landed the leading role in "A Yank on the Burma Road," playing a cab driver who decides to lead a convoy of trucks for the Chinese government.
Nelson entered the Army during World War II and went on the road with other actors performing the wartime play "Winged Victory," which was later made into a movie starring Red Buttons, George Reeves and Nelson.
After the war, Nelson starred in a string of movies, including "Undercover Maisie," "Time to Kill" and "Tenth Avenue Angel."
He is the answer to the trivia question: Who was the first actor to play James Bond? Before Sean Connery was tapped to play the British agent on the big screen in 1962's "Dr. No," Nelson played Bond in a one-hour TV adaptation of "Casino Royale" in 1954.
Nelson switched to the stage during the 1960s and 1970s, appearing on Broadway in "Seascape" "Mary, Mary" and "Cactus Flower." He earned a Tony nomination in 1978 for his role in "The Act," which also starred Liza Minnelli.
"He was a very naturalistic, believable actor," said his agent, Francis Delduca. "He was good at both comedy and the serious stuff."
Among his other film credits were "Airport" and "The Shining," and he also appeared on such TV shows as "Murder, She Wrote," "Dallas" and "Magnum P.I."
More recently, Nelson and his second wife (they married in 1992) spent a lot of time traveling. He planned to write a couple of books about his time on stage and in Hollywood.
Nelson is survived by his wife. He did not have any children from either marriage.
Funeral arrangements were pending.