Let it be known worldwide ... "Nature Boy" Ric Flair is back, baby!!! WOOOOOO!!!

The legendary wrestler just posted a video -- while wearing an incredible t-shirt -- to all his fans saying he's "back up and running."

This is the first time Ric's spoken in person since his medical emergency hospitalized him on August 11, although he did tweet last week that he'd be back.

Naitch made good on his promise just a few days later with this epic promo thanking all his fans for the love and support ... and promising to see everyone very soon.

Hell yeah.