Federer had gone into the final insisting that he believed he could win, despite a 1-8 record against Nadal on clay and having seen the Spaniard demolish all comers on his way through the draw.
And any belief that Federer did have began to disappear almost immediately, as he made four unforced errors to give away a break of serve in game one.
The top seed appeared to be using a more attacking strategy than in past years and the high-risk tactics almost got him back on level terms in game two, but he could not convert a break point and the set ran away from him.
When Federer dropped serve at the start of the second with his 15th unforced error of the match he looked a beaten man, but a superb angled backhand helped him recover the break in the following game.
And as the set progressed, Federer began to suggest he could threaten the champion.
The key moment came at 3-3 when the Swiss earned a break point and a chance to finally move ahead, but Nadal drew him into the net and Federer caught the tape as he went for too much with a low backhand.
With the chance gone, Nadal inevitably made him pay in the next game, taking his third break point by punching a backhand pass down the line with Federer stranded at the net.
Things got even worse for the Wimbledon champion in the third, as he lost his first love set at a Grand Slam since facing Pat Rafter at the French Open in 1999.
In the closing stages Nadal was picking him apart, with one stunning lob in game four a particular highlight and evidence that the Mallorcan's game has come on in leaps and bounds.
He sealed victory when the world number one made his 35th unforced error of the match - to Nadal's seven - and left an embarrassed Federer to pay tribute as the trophy was handed over for a fourth time.
"Rafa is very, very strong and he dominates this tournament like never before," said Federer. "Congratulations Rafa."
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