You better watch your step around WWE Vice-Prez Stephanie McMahon ... because she will literally pulverize your ass if you cross her.

Our proof: McMahon just posted this video of her doing some ridiculous boxing drills ... and holy crap, she is fast.

Coincidentally, we spoke to McMahon just this week in NYC ... and she told us all about her training secrets. Watch the clip.

Suddenly, "fights like a girl" sounds a whole lot scarier.