Snoop Dogg's new favorite UFC fighter has A LOT in common with the rapper -- telling TMZ Sports he's all about that Kush ... and pulled out a fat ass joint to prove it.

22-year-old Sean O'Malley made one helluva first impression on Snoop during his big victory on "Dana White's Tuesday Night Contender Series" this week ... earning a UFC contract in the process.

Snoop is one of the announcers on that show -- and was so impressed with Sean, he smoked the dude out after the fight.

TAKING SOME HITS
UFC
 

Now, Sean tells us he's grateful for Snoop for "medicating me after my fight."

In fact, O'Malley says he looooves the weed -- and thinks the sticky icky is a great thing for all athletes. 

It's at that point, he busts out one of the biggest joints we've ever seen -- while wearing a marijuana bathrobe -- and self-medicates.

Nate Diaz would be proud

SNOOP'S EPIC REACTION
UFC