Jon 'Bones' Jones -- I'm Gonna Beat the Crap Out of Chael Sonnen

It took long enough ... but UFC champ Jon "Bones" Jones will finally do battle with his longtime verbal tormentor Chael Sonnen ... both in the ring AND as opposing coaches on "The Ultimate Fighter."

UFC President Dana White announced the fight earlier today ... confirming the two will face off on April 27. Additionally, the two will serve as coaches to up-and-coming fighters on the FX reality show "The Ultimate Fighter."

Sonnen has been harassing the hell out of Jones for weeks ... ever since Jon refused to allow Chael to step in as a replacement fighter for a Sept. 1 fight when Jon's originally scheduled opponent dropped out due to injury at the last minute.

Chael proceeded to run a campaign of harassment on Twitter ... sending a flurry of messages to Jon ... including, "I know you will never fight me. Don't be afraid. But I'll always be the monster in the closet of your mind, little JJ."