Australia's George Kambosos Jr. has pulled one of boxing's great recent upsets, becoming the unified IBF, WBO, WBA and The Ring lightweight world champion. 

The 28-year-old Sydneysider stunned unbeaten favourite Teofimo Lopez via split decision, 115-111, 115-113, 113-114. 

He knocked down Lopez in the first round, and while Lopez returned the favour in the tenth, the Aussie at times dominated his fancied opponent and did enough to win it on the cards. 

Kambosos was a $6 underdog to win the fight outright and $9.50 to win it via points/decision, but pulled off the incredible upset at a sold-out Hulu Theatre at Madison Square Garden. 

Kambosos scored his knockdown with a perfectly-timed overhand right in a sizzling first round as both fighters came out swinging wildly, backing up a spiteful war of words that lasted nearly a year. 

After an even pair of rounds followed, Kambosos took control in the middle of the fight. 

But Lopez surged back from the eighth round onwards and knocked down the Aussie in the tenth with a chopping right hand after rocking him with a huge straight right in the ninth. But Kambosos regained his feet and battled back brilliantly in the final two rounds to outland his rival 41-16 across the 11th and 12th rounds. Lopez suffered a significant cut over his left eye that forced the referee to call in a doctor in the 11th, and was also cut on his head and right eye. Kambosos himself was left bloodied by a cut to one eye, but looked the healthier of the two warriors when the final bell sounded. 

Kambosos declared: "Have I changed all week? Have I changed all career? Never… I'm not the king, because you've got four kings. I'm the emperor!" 

"I'm the greatest Australian fighter in history," he added. 

Kambosos revealed the words of iconic trainer Cus D'amato ignited the first-round shot that changed the fight - and his career. 

"Cus D'Amato had a great saying, when Muhammad Ali fought an unbelievable puncher in Joe Frazier… 'You hit him with the best right hand you have ever thrown in your life in the first round and change the fight'. 

"That's what I did, I had that in my head. I had that mentality, that I'm going to hit this guy clean, that I'm going to hit him hard and I'm going to put him down. The fight changed after that." 

Kambosos once fought on a Lopez undercard, but in a fight that was 10 months in the making – and had the date changed eight times – he produced one of the all-time boilovers on just his third fight in the US to move to 20-0 with 10 KOs. 

A disciplined Kambosos constantly looked to hit Lopez on the counter as the reigning champion charged in looking for a knockout shot. Behind a well-timed jab and a brilliant overhand right - the shot which dropped Lopez in the opening round - the Australian outworked his rival throughout the 12 rounds. According to CompuBox stats, he landed 155 power punches to Lopez's 115. 

"I won tonight," a bitter Lopez declared. "I ain't no sore loser, I take my wins and I can take my losses... I don't care what anybody says man." 

He added: "The referee knew I won tonight. Everybody knew I won tonight," causing a loud outcry of boos from a crowd which had been heavily in favour of the Brooklyn-based Lopez throughout the bout. 

Lopez went on to claim he won the fight by 10 rounds to Kambosos' two: "I score it 10-2." 

Kambosos hit back, claiming: "You're delusional", before immediately offering a rematch to the beaten champ (now 16-1) on Australian soil. 

"Take it like a champ, let's do it again in Australia," Kambosos says. "80,000 fans in Australia, let's do it again." 

He could also look for a future unification fight against Devin Haney, who holds the WBC lightweight belt. Another option could be a bout with rising star Gervonta Davis. 

Both fighters were immediately taken to hospital following the bout.