British media reported he had been suffering from cancer.
Minter was a bronze medallist at the 1972 Munich Olympics and took the professional world title in Las Vegas in 1980 after beating Italian-American Vito Antuofermo on a controversial split decision.
He stopped the Italian in a rematch that same year in London but lost his title to "Marvelous" Marvin Hagler after three rounds at Wembley Arena three months later.
Minter retired with a 39-9 record.
(Reporting by Alan Baldwin, editing by Ed Osmond)