'Game of Thrones' Star Jason Momoa -- SLAP BATTLE In Atlanta [VIDEO]

Jason Momoa -- the guy who plays the enormous and terrifying Khal Drogo on "Game of Thrones" -- slapped the bejeezus out of some guy in Atlanta last night ... and it was all caught on tape.

The slappee posted the video on YouTube -- after he stupidly challenged the 6’5” "Conan the Barbarian" actor to a game of slaps, and got his ass destroyed.