Raja Jackson -- the son of UFC legend Quinton "Rampage" Jackson -- was arrested on Thursday for brutally beating down a wrestler at an event late last month.
TMZ Sports has learned the 25-year-old was taken into custody early in the morning ... and booked on a felony charge.
Jail records show he's currently still behind bars ... being held on a $50,000 bond.
The arrest, of course, stems from that ugly incident at a Knokx Pro Wrestling event in L.