The strongman-turned-actor, who plays Gregor 'The Mountain' Clegane in the hit fantasy series, won the competition in Leeds last week, after performing a series of strength-testing challenges, reported Contactmusic.
The 400-pound (181.4 kilogram) Iceland native was the only participant to complete the atlas stone challenge, which demands the contestant to lift a heavy concrete sphere onto a large barrel.
"I am the future of strength. I am the King of the Stones!" Bjornsson exclaimed as he ripped off his shirt, after completing the task.