He played Dr McCoy on the original 1960s series but never left American screens thanks to an endless number of syndicated repeats.
His character was one of the most popular in the original series. He reprised his role in six Star Trek films.
Kelley's death, after a long illness, was announced by officials at the Motion Picture and Television Fund Hospital on Friday.
![[ image: width=150]](/olmedia/365000/images/_367110_bones150.jpg)
Leonard Nimoy, who played Mr Spock in the science fiction series, remembered Kelley's kindness.
"He represented humanity and it fitted him well," Nimoy said.
"He was a decent, loving, caring partner and will be deeply missed."
His earlier screen credits include Gunfight at the OK Corral and Raintree County.
Dreamed of being a doctor
In addition to Star Trek, he made appearances on dozens of television shows, including Gunsmoke and Bonanza.
Kelley is survived by his wife of nearly 55 years, Carolyn.
Born DeForest Jackson Kelley in Atlanta, Georgia, on 20 January, 1920, his career dream was to become a doctor like the uncle who delivered him.
But his family did not have the funds to send him to medical school and he drifted into singing and theatre.
A Paramount scout spotted him in a Navy training film and signed him to a contract at the studio as a bit player.
"They (Paramount) tested him because they were looking for a fellow to be in a film called 'This Gun for Hire'," said former Paramount producer AC Lyles, a longtime friend.
"He was a great heavy, in contrast to what he is in person," Lyles said.
Star Trek
Dr Leonard "Bones" McCoy profile (BBC)
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