Ex-NHL tough guy Sean Avery didn't just fight on the ice -- he fought in the middle of an NYC street back in 2013 ... and TMZ Sports has found the video.
We know ... it's old. But it's kind of awesome.
We've confirmed the 37-year-old former New York Rangers star -- who once led the NHL in penalty minutes -- got into it with 2 other men on June 19, 2013 after a verbal altercation escalated.
Avery kicks some serious ass before he got cheap-shotted -- and even the sucker punch did't phase the guy.