If you ever had any doubt about Jake Paul's skills in the boxing ring, the guy just flatlined a UFC legend -- beating Tyron Woodley in the 6th round of Saturday night's matchup.

Of course, Jake was initially slated to go against Tommy Fury, and he had a message for the "Love Island" star after putting Tyron on the canvas.

Check the video -- Jake celebrates the major win ... and says he's ready to face Jorge Masvidal or Nate Diaz to follow up -- calling them bitches in the process.

The win is by far the best of Jake's career -- he took the fight on less than a month's notice after Fury backed out.

The knockout was beautiful. Jake faked to the body, forcing Tyron to drop his hands. Then Paul came over the top with a right that landed flush on Woodley’s ear, sending him falling to the canvas. It was clear Tyron was out, so the referee didn’t count … the fight was over.

As for Woodley, he looked sharp up until the KO. The future UFC HOFer was far more aggressive ... and landed some nice, powerful punches.

Now that Jake erased any doubt this time around vs. Woodley, it seems likely a Paul vs. Fury fight will be in the works.

It all went down at Amalie Arena in Tampa .. and Jake's definitely gonna celebrate his ass off tonight.