NBA's Julius Randle: I'M ENGAGED!!! Check Out The HUGE Rock

Big offseason for L.A. Lakers forward Julius Randle ... who just proposed to his smokin' hot model girlfriend with a diamond that's bigger than her knuckle!!

The 21-year-old NBA player popped the question to Kendra Shaw during a romantic getaway to Greece ... and clearly, she said "Yes."

Randle started dating Shaw during his 1st season at the University of Kentucky -- and decided it was time to lock it up for good!

We're working on the ring details -- but DAMN ... we're guessin' it wasn't cheap.