The ring wasn't the only place for action at Staples Center Saturday night ... 'cause a massive brawl took place in the crowd of the Errol Spence-Shawn Porter fight and TMZ Sports has the video.
We're told the fracas got started after the 4th round when 2 fans started arguing about who was winning the fight.
All hell broke loose after that ... with a co-ed scrap going down and bodies flying everywhere.
The fight lasted for almost a minute.
Security ended up restoring order to the crowd ... and from what LAPD tells us, no arrests where made.
Bonus entertainment ... the guy who taped the brawl giving us a hilarious blow-by-blow of the entire melee.
Next fight, this man needs a microphone.