Post Malone Makes Giants Fan Wear His Cowboys Jacket After a Wow Win

Post Malone is out here rapping Cowboys victories into existence -- and with a crazy win over the Giants, he celebrated in the best way possible ... making the other guy wear your team's gear.

The Texas native was at the Cowboys/Giants game Sunday in NY, where he was surrounded by Giants fans ... one of whom we're told he made a bet with. It was simple -- if my Cowboys win, ya gotta rock my Cowboys jacket. Well, they won all right ... in epic fashion.

With just about a minute left, Dak Prescott threw what you might call a Hail Mary down the field to Cole Beasley, who made an incredible catch in the end zone. At first, it looked like he was out of bounds and the pass was incomplete, but upon further review ... it was ruled a TD.

The Cowboys made a two-point conversion after that and went on to win it 36-35. Post, of course, was ecstatic ... and, of course, followed up on the bet by making the Giants fan put on his Dallas coat. In this clip, obtained by TMZ, you can see the guy was a good sport.

What's even crazier ... Post rapped about this exact same scenario happening in his new single, "Wow." ... almost down to a tee.