The American was the undisputed middleweight champion between 1980 and 1987, during the golden age for the weight category, and arguably the sport. Hagler, Thomas Hearns, Sugar Ray Leonard and Roberto Duran served up incredible bouts.

Hagler's wife made an announcement on the former fighter's Facebook page.

"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. Our family requests that you respect our privacy during this difficult time. With love, Kay G. Hagler."

Hagler made his mark in 1980 by stopping Alan Minter inside three rounds in London. He would then go undefeated for seven years, defeating Duran and Hearns, the latter in a famous bout in 1985. Hagler lost his crown in a split decision to Sugar Ray Leonard in 1987 and then retired, before residing in Italy after hanging up his gloves.

He was named twice fighter of the year by The Ring, and fighter of the decade by Boxing Illustrated.

Hagler's middleweight era was brilliantly chronicled by the late writer George Kimball in the book 'Four Kings'.