One of the last two surviving astronauts of the Project Mercury space program, he had been in hospice care since suffering a stroke in September, The New York Times reported.
John Glenn, who flew the first orbital mission on Feb. 20, 1962, and later became a United States senator from Ohio, is now the last survivor of the original Mercury 7 astronauts.
Carpenter's 5-hour orbital mission in 1962 was beset with technical problems and ended with his Mercury capsule landing far from the intended touchdown site in the Caribbean.
Despite the problems that marred the mission, Carpenter later said it has fulfilled a life-long dream.
"I volunteered for a number of reasons," he wrote in a book of astronaut recollections. "One of these, quite frankly, was that I thought this was a chance for immortality. Pioneering in space was something I would willingly give my life for."
His chance of any subsequent NASA missions was ended by injuries suffered in a motorcycle accident, and Carpenter left the space agency in 1967.
Born in Boulder, Colo., in 1925, Carpenter entered the U.S. Navy in 1949, flying jet fighters during the Korean War and later becoming a test pilot.
He was one of seven military pilots chosen as the Mercury astronauts in April 1959.