Jordyn Woods got one lucky thing for Christmas this year ... a ring -- 'cause she is now engaged to NBA star Karl-Anthony Towns!!!

The couple announced the news in a joint post on Instagram on Christmas day ... captioning the emotional carousel of photos with a simple pun -- "Marry Christmas."

Jordyn -- dressed in all white -- looking as happy as ever with her new fiancé as they stand atop a gorgeous, scenic view at the "Overstory" cocktail bar in New York City.

KAT -- known for his legendary games playing for the NYC Knicks -- is double-dipping in the Christmas celebrations today, being they defeated the Cleveland Cavaliers in a close game, hours before their dazzling announcement.

The high-profile couple started dating back in 2020 after being longtime friends, and bonded over shared experiences of losing a parent ... with Towns' mother passing from COVID-19 and Woods losing her father.