It snapped Djokovic's 26-match winning streak in Grand Slam matches and ended the Serbian's hopes of holding all four of the sport's major prizes simultaneously for the second time, having achieved it by winning his only French Open in 2016.
The clay courts of Roland Garros host the second Grand Slam of the season. Thiem won the encounter 6-4, 6-4 on his way to the title. On the women's side, can Simona Halep defend her title?
The pair have met on 12 occasions with the 11-times French Open champion Nadal winning eight times.
"Credit to him. He just played the right shots and put me out of the comfortable position in the court".
"But I'll try to keep all the positive emotions I'm having right now from this fantastic match today, and go with a really positive mind into the match tomorrow, and then we'll see".
More than an hour after the women's final should have started on another stormy day on Court Philippe Chatrier, fourth seed Thiem thumped a forehand victor past Djokovic to seal victory after squandering two earlier match points.
The semi-final match against Djokovic was played on the Phillipe-Chatrier Court and the full match lasted for four hours and 13 minutes.
Thiem's coach Nicolas Massu said he would prefer the final to be shifted to Monday but the Austrian insisted he was happy to play Sunday.
"When you play in the middle of a hurricane it's hard to play well", Djokovic said.
"I was not unhappy yesterday, because I went to the locker room with 3-1 lead in the third set".
The match lasted two days after it was suspended early in the third set due to rain on Friday. He struck a backhand into the net on Nadal's third break point in the second game.
Thiem leads 4-1 in the fifth set.
There was confusion still about why the match was not concluded on Friday as there was a three-hour spell of dry and breezy weather after the decision was made to call off play.
The top seed broke again for 3-2, held for 4-2 but the dogged Thiem would not relent and brought the set back on serve at 4-4. Austria's Dominic Thiem reacts after his semifinal match against Serbia's Novak Djokovic.
With the bulk of crowd support behind him, Thiem dug deep and stretched to a 4-1 lead in the decider as Djokovic's error count at the net piled up.
"It's just unfortunate. These kind of matches, one or two points decide a victor".
There was one final twist as Djokovic's 53rd unforced error on a wild forehand set up a third match point which the Austrian gobbled up with his 52nd victor.
The Spaniard had never lost to Federer in their five previous French Open meetings, but hadn't beaten the Swiss in their last five matches overall, a run stretching back five years.
