We have photos of The Weeknds 18 year old girlfriend. Incase you didnt know. We're dating

The Weeknd and Bella Hadid made it photographically official Tuesday night ... leaving a club hand in hand.

They've been dating on the down-low for 4 months but last night clearly wanted it known ... they're together as they locked hands leaving Up and Down Nightclub in NYC.

A little background ... she's 18, he's 25.

Good looking couple for sure.