Djokovic needed two more victories to hold all four grand slam titles for a second time but Thiem cemented his status as the heir apparent to Rafael Nadal on clay with a dramatic 6-2 3-6 7-5 5-7 7-5 victory.
The pair battled the weather and their own nerves as well as each other during a two-day roller-coaster that was eventually decided when Thiem planted a forehand into the corner on his third match point.
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His reward, if you can call it that, is a repeat of last year's final, which he lost in straight sets to Nadal.
The Spaniard, who has won all 11 of his previous finals at Roland Garros, was able to put his feet up after defeating Roger Federer in straight sets on Friday.
Thiem said: "To play Rafa here on this court is always the ultimate challenge, one of the toughest challenges sports in general can give.
"But I'll try to keep all the positive emotions I'm having right now from this amazing match today, and go with a really positive mind into the match tomorrow, and then we'll see."
The 25-year-old will need to show the same fighting spirit, physical resilience and tactical astuteness that he did against Djokovic while trying to cut out the nervous moments, such as the two match points he let slip away at 5-3 in a wild deciding set.
Thiem will of course be the underdog, and his cause has not been helped by having to play four days in a row because of bad weather.
He does have youth on his side, and he said: "I'm feeling fine. I'm full of adrenaline, of course, and I will have that tomorrow. So I'm not going to be tired. I'm ready to leave everything what I have out on the court tomorrow."
Thiem had been 3-1 up in the third set on Friday when play was called off for the night, with Djokovic having allowed the extremely windy conditions to get in his head.
The world number one's haste to leave the court led to speculation he had forced the tournament referee's hand in cancelling play when it was not actually raining, but officials insisted it was the stormy conditions that prompted the questionable decision.
Djokovic did not want to elaborate on how the discussions had gone, but said: "Obviously when you're playing in hurricane kind of conditions, it's hard to perform your best. One of the worst conditions I have ever been part of.
"What I was explained yesterday on the court in the first set when I asked the
supervisor, he came on the court and he said as long as there are no flying
objects coming to the court, we're good.
"I didn't know that an umbrella is not a flying object, which flew in in the
first game of the match, but that's their decision. I guess they know tennis
The decision to postpone the match was widely thought to have been in Djokovic's favour but Thiem was also happy, saying: "Conditions were very, very tough yesterday. I think I never played in such a wind."
Djokovic certainly looked more focused on the restart, although it was still breezy and cool, and he quickly retrieved the break only to give the advantage away when he served at 5-6.
The world number one battled back to take the fourth set but was in huge trouble in the fifth at 1-4 when a sharp shower forced another delay.
Djokovic levelled at 5-5 with considerable help from Thiem but for the third time in the set he came unstuck serving into the wind, seeing his winning grand slam run ended at 26 matches.
He insisted the weight of history had not been too heavy and instead chose to praise Thiem for his performance.
"There is always something large at stake when you're one of the top players of the world and play in the biggest tournaments," he said. "It's not any different this time.
"Credit to him. He just played the right shots and put me out of the comfortable position in the court.
"I don't think I have done too much wrong in the entire tournament. This match was always going to be tough because Dominic is a fantastic player on clay – in general, but especially on clay.
"It's just unfortunate. These kind of matches, one or two points decide a winner."