Dricus Du Plessis Celebrates UFC 305 Win By Wearing Mankini

Dricus du Plessis successfully defended his UFC middleweight championship for the first time Saturday, submitting Israel Adesanya in the fourth round ... and he's celebrating the win in style, slamming beers, and wearing a mankini (not necessarily at the same time)!

The 30-year-old fighter left little to the imagination ... posing for the photo with the UFC title on his shoulder -- while wearing the South Africa-inspired thong with some of his buddies.

Du Plessis also celebrated the win by throwing back some beers with his contingent ... slamming a pint in record time!

While there are plenty of people du Plessis credits for helping him get the W on Saturday, he made sure to call out one by name, Drake, who put down a $450k bet on Izzy to win!

Understandably, the champ is living it up following his win ... he defended his title in Perth, Australia, not far from Adesanya's home in New Zealand.

In fact, we spoke with the South African fighter days before he defended his title, and he told us if he had his way, they'd fight in Izzy's gym in Auckland.