The incident went down Wednesday night at the Val Air Ballroom in Des Moines, IA where the rapper was performing. We're told during the concert the fan jumped on stage to score a video with DaBaby.

Witnesses say a security guard pushed the fan into the backstage area and that's where our video begins. You see a massive dude pummeling the fan, who narrowly misses a sock to the face while on the ground. You also see DaBaby -- no shirt but plenty of neck jewelry -- enter and watch.

It's unclear if the guy doing the pummeling is venue security or part of DaBaby's crew.

The West Des Moines PD tells TMZ ...no one filed a police report.

Fans trying to score pics or vids with DaBaby at their extreme peril is becoming a thing. As we first reported ... Donald Saladin -- stage name Don Trag -- sued DaBaby after his crew was caught on video beating him to a pulp back in May outside a Massachusetts club.

Trag, who wanted a pic with the rapper, claimed the beatdown left him in a coma. Just days after that attack ... DaBaby posted video showing he was involved in the beatdown of another man who heckled him at a Louis Vuitton store.

The edited video shows the brawl erupt. It appeared 3 people were involved, but you only see DaBaby, who takes credit for the beating. As we reported ... it's unclear if DB took care of the heckler on his own. It's doubtful, though ... since DB's always surrounded by security.

We reached out to DaBaby's camp for comment, so far, no word back.