DaBaby's Posse Viciously Attacks Overzealous Fan

DaBaby bailed on a concert he was supposed to perform at because of an overzealous fan -- who allegedly became confrontational and handsy ... and, thus, got the crap beat of him by the rapper's crew.

The North Carolina-bred MC was all set to take the stage Friday night at Centro Nightclub in Lawrence, MA -- where he was headlining.  DB never made it in the building 'cause his security team and entourage were too busy beating some guy to a pulp outside ... according to Derek Lemire, who was promoting the event for NTS Entertainment.

We're told the fan wanted a photo with DaBaby, but got turned down. When the dude persisted by asking again, Lemire says he got swarmed by DB's posse ... and took a severe beating.

You can see DaBaby looking on nearby as the dude gets thrashed. He's wearing his signature "KIRK" chain that he's always wearing on stage and social media. We're told the fan was carried away by stretcher and taken to the hospital.

To make matters worse, Lemire tells us that DaBaby completely flaked on the gig ... bouncing after the altercation and allegedly taking the money he was paid with him. Lemire says NTS shelled out $22k for DaBaby, and he's working on getting it back.

A police spokesperson tells us cops responded to the scene early Saturday morning -- but when officers arrived, none of the witnesses would cooperate.

As far as how this went down from the DaBaby's point of view, we're told it was a classic case of look-but-don't-touch. The fan persisted on getting a photo, and when he was repeatedly denied ... the guy allegedly started talking smack and getting handsy with Baby's security. Our sources say the dude touched the hand of the rapper's bodyguard ... and then it was on.