Amber Rose Buys 21 Savage $50k Promise Ring

Amber Rose and 21 Savage are getting seriously serious -- there's a $50,000 ring on his finger to prove it.

We're told the fresh ice the rapper had on his right ring finger at the VMAs is an 18-karat gold promise eternity ring ... and it was a surprise gift from Amber. It's made up of 1,100 stones -- white diamonds and red rubies spelling out "Loyalty 21."

IF & Co. jeweler designed the promise ring for Rose and Ben Baller hand-delivered it in time for the awards show.

On top of the $50k gift, Amber posted she was going to "pounce on" 21 Savage as soon as they got home from the VMAs ... proving he was also one of the night's biggest winners.