Jeff Horn’s defeat of world champion Manny Pacquiao left the world of boxing stunned as he grabbed the World Boxing Organisation welterweight crown on Sunday.

Jeff Horn, nicknamed "The Hornet", grew up in Brisbane and first walked into a boxing club 11 years ago to learn self-defence.

On Sunday he won a brutal fight, in front of a packed hometown crowd at Brisbane's Suncorp Stadium, despite a controversial unanimous points decision, with the three judges scoring the fight 117-111, 115-113 and 115-113 to the Australian after 12 rounds.

Pacquiao's camp slammed the officials after the Filipino lost his World Boxing Organisation welterweight title.

"The referee was sketchy, the judges were crazy," said Pacquiao's strength and conditioning coach Justin Fortune, who is a former Australian heavyweight champion.

Pacquiao is considered one of the greatest fighters of his generation. His camp had predicted a "short and sweet" win over Horn, a 2012 Australian Olympian.

But Horn showed no signs of being overawed by the occasion, relentlessly taking the fight to the Filipino great and not allowing him to find any rhythm.

"I feel like he couldn't get a hold of my gap. I was feinting a lot, trying to upset his rhythm and I think that was working throughout the majority of that fight," said Horn, who stands nine centimetres taller than Pacquiao.

Pacquiao did manage to land some left jabs in the opening rounds to take the early points but Horn refused to back away and his brawling tactics paid dividends through the middle stages.

"He was quick when he put combinations together but I felt controlling the gap made it easier to see the punches coming," Horn said. "The size difference helped too."