The Norwegian managed to end victorious after a strong descent down the Col d’Aubisque despite an initial lead from Jeremy Roy, who was on task to win his first ever Tour stage.
The 33-year-old professional cyclist made a charge to the finish line in the final 40km to secure his 10th Tour stage win.
"This is the best moment of my career,” Eurosport quotes the Norwegian as saying.
“Winning alone after a hard climb like the Col d'Aubisque is incredible. It's the craziest thing I have ever done.
"I took it easy in the mountains yesterday and saved my legs, which is why I won today."