Georges St-Pierre confronted Michael Bisping during a heated face off at a media commitment for UFC 217.
Per TMZ, St-Pierre warned the champion to keep his distance, as Bisping got too close in Toronto, Canada.
St-Pierre said: "Don't touch me, man! Don't touch me. I'm not afraid of you. I don't give a damn."
Bisping touched GSP's face when the pair squared off, causing the angry reaction from the three-time UFC welterweight champion.
Per TMZ, Bisping had already told his future opponent to "keep your hands to yourself," before the men took to the stage on Friday.
UFC Europe provided footage of the incident:
The UFC middleweight champion is due to step into the Octagon with the Canadian superstar on Nov. 4 in New York.