It will be for the third time that Federer will become the world number one.
In the intense heat of battle, with Nadal seemingly occupying every metre of the tennis court, Thiem was the first to crack.
Only Rafael Nadal truly knows what he saw reflected when he glanced into the belly of the big silver bowl, but as he pressed his 11th French Open championship trophy against his cheek, his face began to crumple.
But the Austrian had too many chinks in his game - not enough first serves (57%), 42 errors to 34 winners - to test Nadal for better part of the match.More news: Former Obama Adviser Suggests Trump Is Russia's 'Chief Advocate' and Defender
The problem for the 24-year-old was that his serve wasn't co-operating.
Nadal will have Federer's record of 20 Grand Slams in his sights, and will be hoping to challenge the Swiss at Wimbledon at the start of July. As the players engaged in intense, long-drawn rallies, and only six games of the opening set were over after 40 minutes, there was a feeling that something had to give. Over the last two tournaments, he's lost one set.
A dejected Nadal suffered a stunning loss against Robin Soderling at the French Open. It was his first defeat on the Parisian clay.
Australia's Rosewall was in the crowd on Sunday to see the final, 50 years after he won the title in Paris.
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He followed that up with his second title at Wimbledon with a straight-sets victory over Czech Tomas Berdych. Federer had ended Djokovic's 43-match undefeated run in the semi-finals.
The brutal truth, however, is that this young pretender to Nadal's clay throne was never at the races once Nadal had broken him at 4-4 in the first set. He was presented with the Coupe de Mousquetaires by another legend of the sport, Bjorn Borg. Like so numerous pretenders, Thiem just did not have quite the same level of consistency to derail the Spaniard, who ruthlessly targeted his flowing backhand. He has a record 11 wins at both the Monte-Carlo Masters and Barcelona Open, eight at the Rome Masters (Italian Open) and five more at the Madrid Open.
This year, Nadal dropped just one set in the entire tournament.
It was his most one-sided final win since allowing Federer just four games in the 2008 final.
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Victory at Roland Garros on Sunday proved memorable for Rafael Nadal, with the Spaniard securing his 11th success at the French Open, although he's since made clear that he was bothered by hand cramps in the third set which alarmed him due to the humidity.