"Our girl joined us earth-side this weekend and she's already changed our world. So in love," Hadid said on Instagram Wednesday, alongside a photo of Malik holding the newborn's hand.
"Our baby girl is here, healthy & beautiful. To try put into words how i am feeling right now would be an impossible task. The love i feel for this tiny human is beyond my understanding. Grateful to know her, proud to call her mine, & thankful for the life we will have together," Malik tweeted.
This is the first child for Hadid, 25, and Malik, 27. The celebrity couple have been dating off and on since 2015.
The model told Fallon she was doing her best to enjoy being pregnant amid the coronavirus pandemic.
"Especially during this time, it's a nice silver lining to be able to be home and together and really experience it day-by-day," she said.
Several stars congratulated the couple on their daughter's birth on social media.
"Welcome babygirl! So happy for you guys," Hailey Bieber commented on Hadid's Instagram post.
"Ahhhh!!!!! HUGE congrats!!!!! I can't wait to meet this angel," Olivia Culpo commented.
Hadid's father, Mohamed Hadid, also commented.
"Congrats .. Jido's heart belongs to you.. baby girl," he said.