TMZ Sports has learned ... Bron is the proud new owner of a "Lion Gatekeeper" pendant ... complete with 130 grams of 14k gold, encrusted with 35 carats of VS1 diamonds.

We're told LBJ hit up celeb jeweler Iceman Nick when he was in Houston to play the Rockets ... and the dude pulled out all the stops to come up with a pendant fit for a king.

Of course, LeBron's always been a fan of using lions in his brand ... and Nike once even had a "Heart of a Lion" campaign starring James.

Iceman Nick has a huge list of celeb clients -- from Errol Spence to Tyler Herro to Lonzo Ball, just to name a few.

Not only is it iced out, it's also fully functional -- the eyes of the lion light up and the door knocker moves too!!

LeBron's a big fan of jewelry and can always be spotted with some diamonds on him ... but the light-up piece is gonna change the whole game.