Bjornsson, who portrayed Ser Gregor "The Mountain" Clegane in the HBO series, broke the record at his gym in his native Iceland.
The strongman lifted the barbell for two seconds, before dropping the weights and roaring in delight.
The event was streamed by sports broadcaster ESPN and filmed for Bjornsson's YouTube channel.
Bjornsson, who is 2.05m tall (6ft 9in), previously won the World's Strongest Man competition in 2018.
Speaking in a "behind-the-scenes" video posted on YouTube, Bjornsson said: "I'm extremely proud, you know. I'm extremely happy.