Logan Paul has officially filed an appeal with the California State Athletic Commission, TMZ Sports has learned ... claiming he got screwed by the ref in his fight with KSI.

Paul's beef is with the 2-point deduction the ref issued against him in the 4th round of the Nov. 9 fight at Staples Center in L.A. ... when Paul threw a shot at KSI's head after he was knocked down to the canvas.

"The 2 point deduction was the reason I full out split decision lost the fight," Paul said.

Now, a rep for CSAC tells TMZ Sports ... they received Logan's appeal this week and will begin looking at his case immediately.

"The executive director Andy Foster is evaluating. If there’s sufficient grounds, it’ll go to a hearing at a commission meeting," a CSAC spokesperson tells us.

Paul initially said he wasn't going to appeal the decision or make excuses for the loss -- but after thinking about it and rewatching the fight, he believes it's the right thing to do.

"My team and I have decided to file an official appeal for the fight because we just don't believe that the outcome was right," Paul says.

"By no means am I afraid of losing, but I truthfully 100% believe I did not lose this fight."

Paul says TONS of people -- including pro fighters -- have told him he got screwed by the judges and the ref ... and now he's in complete agreement.

Now, it's in the hands of the Athletic Commission -- which will ultimately decide if the official outcome should be changed.

Stay tuned ...