"Welcome babygirl! So happy for you guys," wrote Hailey Bieber. This comment alone received almost 50,000 likes in just five hours.
"Congratulations Gigi & Zayn!!" Emily Ratajkowski commented, who added three crown emojis to her words.
Gigi's father, Mohamed Hadid, also left a sweet comment under the post in which he promised his new granddaughter his heart.
"Congrats.. Jido's heart belongs to you.. baby girl," he wrote.
Kourtney Kardashian and Patrick Schwarzenegger both left a string of red heart emoji on the upload.
As The Daily Mail covered, it first emerged that the loved-up celebrity couple were expecting a baby together back in April after a "family source" revealed the news. Gigi confirmed the rumors shortly after.
"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," she said at the time, according to the publication.
In recent weeks, speculation ramped up that the supermodel had secretly given birth, which the publication noted was largely triggered by her father sharing a poem he had written to the little one on social media.
Gigi documented her growing baby bump on social media throughout her pregnancy. As recently as September 18, she posted a selection of adorable photos in which she showed off her bump in a crop top as she spent time in the great outdoors.