Spinks, who was born in St. Louis, Missouri, had a stellar amateur boxing career. He won the Olympic gold medal at the Light Heavyweight division during the 1976 Olympics in Montreal, alongside brother Michael Spinks, who also won a gold medal in those games.

Spinks was, alongside Michael, Sugar Ray Leonard, Leo Randolph and Howard Davis Jr. a member of what many consider the United States greatest national boxing team ever. While he was still an amateur, he also became a member of the United States Marine Corps.

He debuted professionally on January 15 of 1977 in Las Vegas, beating Bob Smith by a knockout in five. His next fight marked his debut abroad, as he went to Liverpool, England, beating Peter Freeman by a knockout in the first round. A couple of fights later, he saw a slight improvement in opposition quality, when he fought Pedro Agosto of Puerto Rico and knocked him out in the first. He then drew with Scott LeDoux and beat Italian champion Alfio Riguetti by a decision.

Spinks then ranked number one among the world's Heavyweight challengers, made history on February 15 of 1978, by beating an aged and out of shape Muhammad Ali in a 15-round decision in Las Vegas to become the fastest man ever to win the world's Heavyweight crown when he became champion in only his eighth fight. Ali, who had not been the same since his last fight with Joe Frazier, expected this to be an easy fight. But, with his skills tarnished from years of fighting, and with his lack of training before the fight, he was out hustled by Spinks who never seemed to tire in the bout. This fight is regarded as one of the biggest upsets in boxing history.

Spinks was known to be a party animal during his period as world Heavyweight champion, always enjoying the night life and in the company of multiple women. He even hired a young Mr. T to be one of his bodyguards during that time.

Spinks was stripped of his world title by the WBC for refusing to defend his title against their #1 ranked contender (Ken Norton). Spinks instead agreed to fight a return bout against Ali for the WBA crown. The WBC subsequently named Norton its champion - the first time a boxer had been awarded the heavyweight title without winning it in the ring. Spinks, hence, would be the last undisputed Heavyweight Champion until the emergence of Mike Tyson.

The second Ali fight was different from the first, Spinks losing the title to Ali in New Orleans on September 15, 1978 by unanimous 15 round decision. This time it was Spinks who did not train hard enough, and Ali, despite his skills declining even further, gave every ounce of himself in this fight, doing everything he could to out-smart and out-box the much younger Spinks. By regaining the title, Ali became the first three time Heavyweight Champion, though these two fights probably caused Ali's health to decline even further. Spinks would continue to come into fights out of shape, and would never again be as effective as he was in the first Ali fight, and is thus regarded by some as the worst Heavyweight Champion of all time.

In his next fight, his only bout of 1979, he went to Monte Carlo, where he was knocked out in the first round by future world Heavyweight champion Gerrie Coetzee.

He had a good rebound year in 1980, however, beating former world title challenger Alfredo Evangelista by a knockout in five, drawing in ten with Eddie The Animal Lopez and beating the WBC's number one ranked challenger Bernardo Mercado by a knockout in nine, on the night that Ali challenged Larry Holmes to try to become the first boxer to win the world Heavyweight title four times.

After that win, Spinks found himself challenging for the world's Heavyweight championship once again. In what was the only time he stepped into a ring in 1981, he faced Holmes in Detroit on June 12, getting knocked out in the third round.

In 1982, Spinks decided to go down in weight and compete in the Cruiserweights. He beat fringe contender Ivy Brown by a decision in ten, and former and future title challenger Jesse Burnett by decision in twelve.

His comeback was, once again, stopped on its track in 1983 by the twice former and twice future world Cruiserweight champion Carlos De Leon, who knocked him out in six rounds in that year's only bout for Spinks.

He took 1984 off, but then came back in 1985, winning five bouts and placing himself in line for another world title try. He beat, among others, Franco Thomas that year.

That year also, he made history once again, this time around without having to lace a glove to do it: When his brother Michael beat Holmes on September 21, the Spinks became the first pair of brothers to be world Heavyweight champions.

In 1986, Spinks had another chance to become world champion, but he lost to the WBA's world cruiserweight champion Dwight Muhammad Qawi by a knockout in six in his second attempt at being a two time world champ. Then, he was defeated in six by knockout by Rocky Sekorski.

Spinks boxed for eight more years, having mixed results. In 1994 he lost a bout by KO to John Carlo, noteworthy for being the first time a former heavyweight champion had ever lost to a boxer making his pro debut. He retired after losing by decision in eight to Fred Houpe in 1995, and he was homeless for a period of time. During the late 1990s, however, he was picked up by Tri Star Sports Promotions to become a headliner on their year-round, touring autographs shows. His life is basically now spent on the road, living at Marriott hotels, because Marriott is a sponsor of Tri-Star's shows. Despite the fact he is making a living out of signing his name, he still remains a willing free autograph signer.

His son, Cory Spinks, held the undisputed Welterweight title for a time and was a respected Champion before losing the title by knockout.

Leon Spinks presently, April 2005, is living in Columbus Nebraska, where he works weekends cleaning up the local YMCA. He also volunteers three days a week in an after school program with youth. He keeps a low profile in Columbus occasionally being recognized as a former Champion. He describes his life as comfortable. To most in the town, he's just Leon, no more, no less. (Steve Sipple, "Ex-champ Leon Spinks cleans up in Columbus," Lincoln Journal Star, April 4, 2005)

Spinks had an overall record of 26 wins, 17 losses and 3 draws as a professional, with 14 knockout wins.