The Game of Thrones actor revealed the news on Saturday in a heartwarming image posted to Instagram, showing himself, his wife, their 3-year-old son Freddie and newborn daughter Truly Rose laying together in the family's bed.
"So my amazing wife @laurahopperhops gave birth to our second beautiful child," the 33-year-old English actor captioned the cute photo. "Welcome to the world, our baby daughter, Truly Rose Hopper. Weighing 8lb 1oz."
"Family bed times just got even more cozy," he added, along with a trio of heart emojis.
The following day, Hopper -- who plays Dickon Tarly on the seventh season of HBO's hit fantasy drama -- followed up with a slideshow of photos showing him shirtless, cradling his infant daughter to his chest while still in the English hospital where they welcomed their baby girl.
The actor used the sweet post to explain the importance of a parent sharing skin-to-skin contact with their babies soon after welcoming them into the world.
"I feel like the luckiest guy on earth. There is no feeling like the skin on skin i’ve had with our beautiful children after their births. An immediate and unique bonding process that is the most beautiful of moments to experience as a parent," he wrote. "Their hearts beating next to yours for the first time, and your body warmth keeping them comfortable and secure. A true blessing to be able to give and it’s nature at its finest."
Hopper went on to explain how he felt "lucky to have had this experience with both our babies straight after they were born," and called the bonding opportunities "memories that I will treasure forever."
"I feel so incredibly lucky to have another beautiful baby. But boy did I have the most magical birth," she wrote, before praising the National Health Services hospital for their kindness and superb treatment during her pregnancy journey.
"The #nhs hospital I used went above and beyond to ensure I had the best experience. The wonderful midwives, nurses and NICEST consultant. Thank you from the bottom of my heart from me and my little girl," she wrote.