The American was in just his eighth fight as a professional when he stunned Ali and the boxing world in 1978, was diagnosed with advanced stage prostate cancer in 2019.
Spinks won gold at the 1976 Olympics in Montreal then rose to greater prominence a little more than 18 months later, given the nod via split decision to stun Ali and claim the WBC, WBA and lineal heavyweight titles.
In one of the biggest upsets in the history of the sport, Spinks defied his 10-1 underdog odds with bookmakers to prevail after 15 rounds, winning 145-140 and 144-141 on two scorecards while a third went in favour of Ali 143-142.
His reign lasted exactly seven months as a sharper and fitter Ali gained revenge in an immediate rematch in September 1978, becoming the first ever three-time lineal heavyweight champion after a wide points win.
There would be no trilogy bout and though Spinks did get another opportunity for heavyweight glory in June 1981, there was no fairytale result this time as he was beaten up and stopped inside three rounds by Larry Holmes.
Spinks then dropped down to cruiserweight but was defeated by WBA champion Dwight Muhammad Qawi in 1986. He boxed on for another nine years and finished with a modest record of 26 wins, 17 defeats and three draws.
Additional reporting by PA.