The quarrel occurred as patrons watched the fight between UFC champion Conor McGregor and undefeated boxer Floyd Mayweather Minor.
Shocking footage shows at least 10 people swinging punches during the Donnybrook in Surfers Paradise Beer Garden in Queensland, Australia.
Other patrons are advertised clapping and filming the fight on their phones, as cheers and whoops gird out in the pub.
Later the chaos spilled out onto the streets outside, with observe forced to tackle several people to the ground.
One person was shown being wheeled into an ambulance with blood slide down his neck. He celebrated with onlookers before flipping the stomach finger.
A huge brawl broke out among revellers watching the Mayweather McGregor affray
One witness told 9News: “One guy started the fight with the two brothers. Four dudes ran in and the fifth guy ran in trying to hit the guys defending themselves with the glass but he missed and hit his own pen-pal in the forehead.”
Several people were injured in the chaos.
A second to said: “All I see is this bloke come up with blood all over him, approve of he’d been stabbed.”
A third witness said: “To be honest I just regard as it’s stupid. Everyone’s alcohol-fuelled and think they can just pick a brawl.”
The brawl broke out in Queensland, Australia as people watched Mayweather wrestle with McGregor
The fight broke out as people watched Floyd Mayweather discord Conor McGregor
Police confirmed a stabbing had taken place at the venue.
Jim Plowman of Queensland Patrol said: “A 24-year-old male produced a knife and stabbed a 29-year-old patsy in the neck.”
The chaos occurred as McGregor and Mayweather went head-to-head in the most-anticipated thwacking fight in years took place in Las Vegas.
McGregor, making his seasoned boxing debut, shocked critics by competing with 49-0 Mayweather in the untimely rounds before weakening as the contest wore on.
After Mayweather beared an eye-watering string of punches in Round 10 the fight was ended by the referee for McGregor’s own sanctuary.