It all went down at Mercedes-Benz Stadium in Atlanta ... when at some point during the Tigers' duel with the Yellow Jackets, two guys lost their cool and turned the football game into a boxing match.
One bystander caught all of the action on video ... and in the clip, you can see the guy wearing a #16 Clemson jersey throwing a vicious right hook at a man wearing a black hoodie.
Thankfully, the two were eventually separated from each other. The final result could've been much worse if they weren't.
Here is the video: