Sources tell TMZ Sports ... the Cleveland Browns star pretty much has a mansion in his mouth now ... after hitting up celeb dentist Dr. Thomas Connelly to get some natural porcelain veneers done.

But, the 28-year-old didn't ask for your regular pearly whites ... he wanted his on a different level -- framed with a load of diamonds ... and Connelly delivered!

OBJ's new teeth look AMAZING ... with a iced-out cross on his fang and the back of his teeth -- on both sides -- infused with gems.

We're told Connelly -- who's made icy teeth for Post Malone and Chris Brown -- did a 28 unit full mouth reconstruction ... and it carries 13 carat diamonds!!!

The 3-time Pro Bowler dropped $1.8 MILLION on his new teeth ... but it won't hurt his pockets -- he's made over $60M in his NFL career so far.

It'll be nice to see the guy get back on the field after going down with a season-ending injury in November 2020 ... but wear a pair of shades if you stare at his smile ... just in case.