The supermodel, who is 25, and the former One Direction singer, 27, confirmed the arrival of their daughter in separate posts on social media.
"Our girl joined us earth-side this weekend and she's already changed our world. So in love," Hadid captioned a black-and-white photo of their daughter's hand wrapped around one of Malik's fingers.
Malik also expressed his joy with an announcement featuring a similar photo of his hand intertwined with his little one's.
"Our baby girl is here, healthy & beautiful," Malik's post on Instagram and Twitter begins.
He added: "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 x"
Hadid confirmed she was expecting with her boyfriend in April during an appearance on "The Tonight Show with Jimmy Fallon."
"Obviously, we wished we could have announced it on our own terms but we’re very excited and happy and grateful for everyone’s well wishes and support,” Hadid said, referencing rumors of her pregnancy at the time.
She continued: “Especially during this time, it’s a nice silver lining to be able to be home and be together and really experience it day by day.”
In July, Hadid conducted a livestream and explained why she was keeping a low profile during her pregnancy.
"Obviously, I think a lot of people are confused why I'm not sharing more, but like, I'm pregnant through a pandemic," she said.
Although last month, the runway star did get candid with fans by sharing stunning baby bump photos from a photoshoot. Her growing belly was on full display as she posed in a variety of flowing, loose dresses.
"Growing an angel :)" she captioned the pics.
"Cherishing this time. Appreciate all the love & well wishes. Will never forget creating these special images with my friends @luigiandiango @gabriellak_j @erinparsonsmakeup thank you. I love you!" Hadid added.