The world of heavyweight boxing can be a fickle place.

One moment you could be the globe trotting, world conquering champion, the next you could find yourself flat on your back, staring into the lights and wondering what on earth just hit you.

Heavy weighs the head that wears the crown atop the world of the heavyweight with every opponent under the sun actively plotting your downfall.

Your throne is always under threat and your titles coveted by any number of enemies, who, regardless of rank or reputation, think themselves more than capable of laying waste to your career.

Over the years, there have been a myriad of spectacular upsets with some of the biggest names in the game falling afoul of the curse of being named favourite for a blockbuster bout.

So, here at GIVEMESPORT, we thought we would rank the top ten biggest upsets ever seen in the heavyweight division.

10. Michael Moorer loses to George Foreman 1994

At 45 years old, Foreman was considered a complete no-hoper for his bout with the powerful Moorer.

With Moorer undefeated in 35 fights and Foreman well into the twilight of his career, this one could surely only go one way.

However, the wily old competitor that is Foreman went off script, smoking Moorer with a massive blow in the tenth round.

Moorer folded like a lawn chair and the rest is history.

9. Wladimir Klitschko loses to Corrie Sanders 2003 

Klitschko was listed as the 1/20 favourite for his fight with the little-known South African.

However, using some scintillating and explosive power, Sanders knocked the formidable Ukrainian down three times within the opening round.

It proved to be one of the most humbling losses of Klitschko's long career.

8. Muhammad Ali loses to Leon Spinks 1978

Has there ever been a bigger scalp in boxing than Muhammad Ali?

Ali was still expected to steamroll Spinks despite being in the final years of his career but it was Spinks who would outbox and outsmart the weary veteran.

Spinks, who would win on points, was instantly catapulted into the limelight.

7. Anthony Joshua loses to Andy Ruiz Jr. 2017

One of the greatest underdog fairytales of modern day boxing.

Many felt like chucking 'out of shape' Ruiz into a ring with the physical adonis that is Anthony Joshua was like leading a lamb to slaughter.

However, Ruiz showed some frightful power as he dismantled the British superstar to claim the win.

6. Mike Tyson loses to Evander Holyfield 1996

Tyson was considered the 1/25 overwhelming favourite for his first bout with Holyfield.

Many admired Holyfield for his bravery in returning having stepped away from boxing due to a heart complaint in the early 90's.

They admired him a whole lot more after he stepped up and took Tyson to school with a sublime masterclass of heavyweight boxing. He eventually claimed a TKO in the eleventh round.

5. George Foreman loses to Muhammad Ali 1974

One of, if not the most famous fight in the history of the heavyweight division.

With Ali heading into the tail-end of his career and Foreman proving to be a fearfully ruthless champion, 'The Rumble in the Jungle' was tipped to be rather one sided.

However, Ali would go on to shock the world once again, absorbing a tirade of monstrous blows before flattening an exhausted Foreman in the eighth round.

4. Max Baer loses to James J. Braddock 1935

A fairytale story that has since been made into one of the most beloved sporting films of all time.

Braddock - The Cinderella Man - was a 10/1 outsider when the opening bell rang out but he did the unimaginable when he dismantled the much-fancied Baer.

The Maddison Square Garden bout was shrouded in mob conspiracies which have seen it fall lower in our ranking but it simply can't be denied that Braddock's win is still one of the greatest sporting moments ever.

3. Lennox Lewis loses to Hasim Rahman 2001

It is safe to say that Lewis grossly underestimated Rahman.

Instead of arriving early for the fight in South Africa to acclimatise, Lewis stayed in America to reprise a cameo role in the Hollywood blockbuster Ocean's 11.

The result was that he was thoroughly unprepared for both the man and the environment with Rahman taking full advantage in the fifth round.

2. Sonny Liston loses to Cassius Clay (Muhammad Ali) 1964

Liston had been such a dominant force in the heavyweight division that few gave Clay - who would later become Ali - any sort of hope.

However, never has Ali's 'float like a butterfly sting like a bee' mantra been better epitomised than in this fight.

He took the 'Grizzly Bear' apart, with Liston ultimately retiring on his stool at the end of the eighth round.

1. Mike Tyson loses to Buster Douglas 1990

Tyson only has himself to blame for this stunning upset.

At the height of his 'Baddest Man on the Planet' days, Tyson didn't even bother to train for the fight in Tokyo.'

Instead, he chose to continue partying and sleeping around and, as a result, arrived in the ring woefully out of shape and overweight.

Douglas, a 42/1 outsider, was seeing stars after a brutal Tyson uppercut but somehow hauled himself off the canvas to go again.

In the tenth, he completed the stunning upset with a flurry of venomous blows that sent Tyson sprawling to the floor.