Raja Jackson Arrested For Brutal Wrestling Ring Beatdown

9/19 -- 5:09 AM PT -- TMZ Sports has learned Raja Jackson was booked on a felony charge of battery with serious bodily injury.

He's already bonded out, a jail official tells us.

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.A., where Raja slammed Syko Stu (aka Stuart Smith) to the mat, and then pummeled him with nearly two dozen punches as he was unconscious.

Mercifully, after 10-11 seconds of repeated blows, other wrestlers stepped in, and pulled Raja off Smith.

The wrestler -- who had gotten into a spat with Raja just before the event -- spent several days in the hospital with numerous injuries, including a fractured maxilla bone. Thankfully, he's since been released and is recovering at home.

For Rampage's part, he's actually stated his son should spend some time in jail for his behavior ... adding "a little community service," anger management courses and therapy would be good for Raja as well.