NBA Star Charlie Villanueva -- ENGAGED TO VIDEO MODEL ... With Huge Engagement Ring

Dallas Mavericks star Charlie Villanueva is ENGAGED ... and he popped the question with a little help from a MASSIVE diamond ring!

The 30-year-old power forward proposed to his GF Michelle Game -- a model who's also appeared in a bunch of music videos for stars like 50 Cent and Meek Mill.

Michelle posted pics of the rock on social media -- and wrote, "Last night I said yes to the love of my life. I couldn't be happier to spend a lifetime with my best friend."

She continued, "He fills a part of my heart that makes me whole, and I'm so happy I wanted to share with you all. I love you."

Michelle tells us Richie from Leon Diamond in NYC helped pic out the 6-figure rock, which is colorless, and nearly flawless.

Congrats!