Four-time WWE world champ Daniel Bryan is BACK -- medically cleared to return to the ring after over 2 years away from pro wrestling ... the WWE just announced.

The 36-year-old was forced into an early retirement in Feb. 2016 after suffering "at least 10" concussions and post-concussive seizures ... but the WWE says he's got the green light to strap on the boots after seeing a number of leading neurosurgeons and neurologists, as well as WWE's Medical Director.

Bryan has been serving as the General Manager of 'SmackDown Live' ... but this effectively opens the door for him to be an active competitor at WrestleMania 34 in April.