It's over ... UFC legend Georges St-Pierre just officially announced his retirement from mixed martial arts -- saying, "It takes a lot of discipline 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 16 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.