TMZ was outside Supperclub on Hollywood Blvd. speaking with rapper Rich Rick ... when suddenly a brawl broke out behind him ... and a man was knocked to the ground.
The group -- consisting of at least 5 men -- stomped on the victim's head repeatedly ... and some of the men threw punches. At no point, do we ever see the victim attempt to fight back.
Eventually, some bystanders pulled the attackers off the victim ... who lay motionless on the ground.
The victim later got up ... and though he was obviously discombobulated and bleeding ... he managed to walk away.
Law enforcement tells us ... no arrests have been made.