Desiigner got into a heated exchange with a fan who was egging him on during his concert, and even took a healthy swing ... after being called a knock-off version of Future!
We've obtained video of the incident ... and it's pretty wild. You see Desiigner beefing with the trash talker before trying to grab the man's shirt, and then throwing a left hook!
We're told the heckler kept yelling at Desiigner during the set, calling him a Future rip-off. When the NYC rapper reaches his boiling point, he gets in the man's face and pulls a punch -- but it's a swing and miss.
It all went down during Desiigner's concert Monday in Denmark, and it appears the incident might've had a carryover effect ... 'cause the rapper says he got kicked off a plane later that evening.