Game of Thrones star Hafþór Júlíus Björnsson has welcomed a baby son with wife Kelsey Henson.

The actor, who played Gregor ‘The Mountain’ Cegane in the series, took to Instagram to share a very detailed breakdown of the day their son joined them in this world.

He started with the moment his wife told him her water had broken at 6 am. He commended his wife saying she “did amazing” and “was in complete control of her mind and body,” as he revealed that Kelsey gave birth in a birthing pool.

He wrote, “I am completely in awe of how strong she is, and so proud of her for everything she did to prepare herself throughout her pregnancy. It cannot be put into words how proud I am and how I feel about this experience.”

At 11:19 am on Sunday, the son made his grand entrance into the world, weighing 3530 grams and 52cm.

The couple has picked a name for the baby but rather keep it a secret now, but Hafþór added they “cannot wait to share it with you all soon.”

He also shared a string of pictures, which was taken moments after their son arrived.

Congratulations to Hafþór and Kelsey!