Wawrinka withstood a fightback from the world number one, who was struggling with a back problem, to come through 6-3 6-2 3-6 6-3.
The 28-year-old becomes only the second Swiss man to win a Grand Slam singles title after 17-time champion Roger Federer
And he is the first man outside the ‘big four’ of Nadal, Federer, Novak Djokovic and Andy Murray to win a Grand Slam since Juan Martin Del Potro at the 2009 US Open.
Fortunes fluctuated wildly over the course of two hours and 21 minutes as Wawrinka opened in scintillating form before a tearful Nadal appeared close to quitting at two sets down, only to stage a remarkable recovery in the third.
The Spaniard, 27, showed great spirit to hit back once again from a break down in the fourth, but a forehand winner gave Wawrinka the decisive break at 5-3 and he served out the biggest win of his life with a love game.
“I still think that I’m dreaming,” said Wawrinka. “It’s a strange feeling. I saw so many finals. I always try to watch the finals of Grand Slams because that’s where the best players are playing.
“Before today, for me it wasn’t a dream. I never expected to play a final. I never expected to win a Grand Slam. And right now I just did it.”
Nadal, who revealed he felt the back problem in the warm-up, said: “It is a tournament that I really had some troubles physically in my career and is something that is painful for me.