Boxing legend Marvin Hagler, the undisputed middleweight champion from 1980 to 1987, died on Saturday at age 66, his wife said.
In a posting on the famed fighter's Facebook page, Kay G. Hagler said her husband passed away at the family home.
"I am sorry to make a very sad announcement. Today unfortunately my beloved husband Marvelous Marvin passed away unexpectedly at his home here in New Hampshire," she wrote. "Our family requests that you respect our privacy during this difficult time."
"Marvelous" Marvin Hagler fought from 1973 to 1987 and delivered some of the epic bouts in a golden era of the sport, finishing with a record of 62-3 with two drawn and 52 knockouts.
The southpaw's most heralded triumph came in a 1985 matchup at Caesars Palace in Las Vegas against Thomas "Hitman" Hearns that lasted only a tick over eight minutes but was regarded as a classic.
After a first-round filled with power punches in which Hearns suffered a broken right hand, Hagler suffered a cut to the head early in the second.
A ringside doctor examined Hagler in the third round and the fight went on. Hagler wobbled Hearns with a powerhouse right and sent him to the canvas moments later, Hearns rising only to collapse into referee Richard Steele's arms.
Hagler won the World Boxing Council and World Boxing Association middleweight titles in 1980, stopping Britain's Alan Minter in the third round at London's Wembley Arena, and added the International Boxing Federation's inaugural title in 1983.
Hagler defended the undisputed crown 12 times, including a 15-round unanimous decision victory over Panama's Roberto Duran in 1983 and his final triumph, an 11th-round knockout of unbeaten Ugandan John Mugabi in 1986.
"Marvelous Marvin Hagler was among the greatest athletes that Top Rank ever promoted," legendary US promoter Bob Arum said. "He was a man of honor and a man of his word, and he performed in the ring with unparallelled determination.
"He was a true athlete and a true man. I will miss him greatly," Arum added of Hagler, a member of the middleweight division's "Four Kings" of the 1980s along with Hearns, "Sugar" Ray Leonard and Duran.
Over a decade from 1976 to 1986, Hagler went unbeaten with 36 wins and a draw.
Named Fighter of the Year in 1983 and 1985 by the Boxing Writers Association of America, he was named Fighter of the Decade in the 1980s by Boxing Illustrated.
He carried a 16-fight win streak into what proved to be his final fight, a showdown with Leonard in 1987 at age 32.
Leonard, coming off three years of retirement at age 30, captured a controversial 12-round split decision and launched his return to the ring as Hagler - angered by the scoring -- bid farewell.
After stepping out of the ring, Hagler pursued acting and a career as a boxing commentators. He was inducted into the International Boxing Hall of Fame in 1993.