In only his eighth professional fight, he won the undisputed heavyweight championship in 1978 after defeating Muhammad Ali in a split decision, in what is considered one of the biggest upsets in boxing history.

Spinks was later stripped of the WBC title for facing Ali in an unapproved rematch seven months later, which he lost by a unanimous decision.

Besides being heavyweight champion and his characteristic gap-toothed grin (due to losing two and later all four of his front teeth), Spinks gained notoriety for the disaster which befell his career following his loss to Ali.

[4] Spinks won three consecutive national AAU light heavyweight championships from 1974 to 1976, the first of which came against future champion Michael Dokes.

[9] Spinks debuted professionally on January 15, 1977, in Las Vegas, Nevada, beating Bob Smith by knockout in five rounds.

[15] Spinks won the world heavyweight title in his eighth professional fight, the shortest span in history.

Spinks's next fight, his only one in 1979, was at Monte Carlo, where he was knocked out in the first round by future WBA world heavyweight champion Gerrie Coetzee.

[27] Spinks was due to face the World Cruiserweight number one David Pearce, but the fight was called off on 24 hours notice after the fighters had both weighed in, due to the BBBoC stance on Pearce fighting abroad in the newly formed Cruiserweight division.

[29] In the 1980s Leon Spinks competed in several boxer vs. wrestler matches in New Japan Pro-Wrestling (NJPW), including losing by submission to Antonio Inoki.

In 1994 he lost a bout by KO to John Carlo, the first time a former heavyweight champion had lost to a boxer making his pro debut (promoter Charles Farrell later admitted to falsifying Carlo's record in order to get the fight sanctioned by the District of Columbia).

[33] On October 9, 1986, Spinks lost to Japanese legend Antonio Inoki in a mixed martial arts fight for New Japan Pro Wrestling.

[34] Spinks made an appearance for the United States Wrestling Association on June 25, 1990, where he lost to Jerry Lawler by disqualification.

In 1991, Spinks made his debut in Japan for Frontier Martial-Arts Wrestling (FMW) teaming with fellow boxer Rufus Blackborn.

[41] Leon's son, Cory Spinks, held the undisputed welterweight title, and was the IBF junior middleweight champion twice.

[44] Spinks perceptibly slurred his words after his active boxing days, and was diagnosed in 2012 with shrinkage in his brain, which doctors said was likely caused by the accumulated punches that he took during his career.