Lyle, who tangled with the likes of Muhammad Ali and George Foreman during the golden days of the heavyweight class in the 1970s, was admitted Nov. 18 with a stomach abscess that had become septic, his sister, Sharon Dempsey, said.
Lyle never won the heavyweight title, but he was a mainstay of the boxing scene in the 1970s along with Ali, Foreman, Joe Frazier and Ernie Shavers.
"Ron was a good-hearted guy, but he could fight like hell," said Shavers, who squared off with Lyle in 1975. "He was tough. He could take a good punch."
Lyle learned to box during a prison stretch for the second-degree murder of a gang rival. He turned pro at the advanced age of 29 and went on to participate in a trio of golden-age bouts against Ali, Foreman and Shavers. He beat Shavers but lost to Ali on a TKO and a late knockout by Foreman.
Lyle retired with a professional record of 43-7-1, with 31 KOs. He recently coached boxing for kids with the Salvation Army in Denver.
Funeral arrangements were not immediately announced.