The couple was spotted in London on Tuesday running errands with a baby boy strapped to Leslie's chest.
The Game of Thrones couple announced their pregnancy this past September, and confirmed the birth of their child today.
The couple initially fell for each other on set of the show, Rose playing opposite of Kit's character Jon Snow from 2012 to 2014. The two's romance was rumored starting in 2012, before they confirmed an official relationship in 2016. They tied the knot in June 2018.
Rose first announced her pregnancy by appearing on the cover of UK's digital MAKE Magazine, debuting her baby bump. She shared with them:
"What a glorious thing to be able to run to the countryside and recoup. It's a great privilege to be surrounded by greenery, birdsong and hedgerows, and our delightful neighbours. It's so peaceful."
A source confirmed the birth of the boy with Page Six, saying the couple is "very, very happy!"
Harrington previously has shared his desire and preparedness to be a father in an interview with InStyle in April 2019. Regarding the Game of Thrones series finale, the actor confessed:
"The most important job I'll ever have is about to finish. Well, not the most. Hopefully, I'll be a father."
We are wishing the best of luck and congratulations to the new parents!