When you're a world class athlete with an insane physique -- you don't hide your body behind a big baggy Halloween costume ... just ask stars like Giancarlo Stanton!
The MLB slugger got decked out like a pharaoh to party his face off -- while MMA stars like Cody Garbrandt broke out the S&M gear.
Floyd Mayweather, Mike Vick, Paulina Gretzky, Bryce Harper and more ... they all dressed up for Halloween and we got the pics!
Enjoy the candy hangover.