Georges St-Pierre Retires, 'You Should Retire On Top'

It's over ... UFC legend Georges St-Pierre just officially announced his retirement from mixed martial arts -- saying, "It takes a lot of discipline, though, to retire on top."

The 37-year-old is widely considered one of the greatest UFC fighters of all time -- some say the best -- racking up a 26-2 record and 3 UFC titles in his 17-year career in the Octagon.

GSP has signature victories over stars like Nick Diaz, Matt Serra, Matt Hughes, Carlos Condit, B.J. Penn (twice)... and most recently Michael Bisping.

During his press conference, GSP thanked Dana White, Frank and Lorenzo Fertitta and other key UFC people.

He also thanked UFC legend Royce Gracie for inspiring him to start MMA back in the day, and thanked Wayne Gretzky for being such an influential Canadian role model.

"I always wanted to be like Wayne Gretzky."

GSP says he's not sad about retiring -- "No tears, I'm very happy to do it."

"It takes a lot of discipline to retire on top ... you should retire on top and that is very hard to do."

As for one final fight with Khabib Nurmagomedov, Georges said he started negotiating with Khabib's camp but "the UFC had other plans."

"I wish Khabib the best of luck. I think he's the best fighter right now ... he's a great guy. I love to watch him fight and I can't wait to see what's next for him."