The model and the former One Directioner have been dating for over two years.
"Love this man more than I could ever put into words, & am inspired by his drive to be and do better everyday," she captioned a video them cuddling up. "Cheers to YOUR YEAR my @zayn – happiest happiest birthday & 25th year of life !! I'm proud to be by your side x."
She also shared an image of the duo kissing and others of Zayn on the rural farm he's been at since last summer.
Gigi and Zayn don't often hide their affection for each other. The duo often gushed about one another on social media, and they've shot magazine covers together as well.
On Gigi's birthday last year, he called her "my everything."
Gigi and her beau first began dating in November 2015. They've had a few hiccups in the road, but seem fully in love. Over the years, there were even rumors that two had gotten engaged after Zayn debuted a tattoo of the word "love" on his right knuckle. At the same time, Gigi was spotted wearing a ring on that ever-so-telling finger.