With Vincenzo Nibali and Alberto Contador having already been dropped, Froome attacked his remaining rivals with 6.4km left of the climb to the ski resort of La Pierre-Saint-Martin and went on to win by 59 seconds from runner-up Richie Porte as Team Sky completed a one-two on the day.
Nairo Quintana (Movistar) finished 1min 4sec down on Froome in third, but the other pre-race favourites suffered heavy losses on the 15.4km ascent.
