The couple welcomed their daughter on Friday, Sept. 12, multiple sources confirmed to Us Weekly.
Having co-starred in the 2012 flick "The Place Beyond the Pines," Mendes, 40, and Gosling, 33, reportedly started dating in 2011.
In July, Mendes' pregnancy was confirmed by People, after news broke that the star was already seven months pregnant with the hunk's child.
"Their lives completely changed as soon as Eva got pregnant. They used to travel all over the place together and go on hikes with their dogs. [But in the past few months] she barely left the house," an insider previously told People. "Ryan has been taking care of her, picking up food and running errands. He has been very supportive of keeping things a secret."
Despite that the notoriously private couple never confirmed nor denied the news, the source said: "This has been a long time coming. Ryan and Eva definitely discussed children before. She knows how much he wants to be a dad and he's going to be an amazing father."
Mendes first sparked pregnancy rumors earlier this year when she refused to go through a full-body scanner at LAX airport in L.A., according to E! Online.
However, the brunette beauty later laughed off the rumors during an appearance on "The Ellen DeGeneres Show," Daily Mail has learned.
"It's so ridiculous," she told the talk show host in February. "It all started because I didn't want to go through the scanners at the airport. You know those X-ray scanners, which are really creepy? They basically see you naked, right? And not only that, but there's a radiation aspect to it, so I always opt out."
Gosling reportedly was very supportive of his girlfriend as they prepare for the arrival of their first child. "Ryan goes out and gets the groceries. [Eva's] been wanting pasta, and he's cooking her meals," an insider previously told Us. "Ryan has already stepped into the role of caring father-to-be."
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