Spain's Carlos Alcaraz recovered from a woeful start to beat an inconsistent Jannik Sinner 2-6, 6-3, 3-6, 6-4, 6-3 and qualify for his maiden French Open final after a see-saw encounter on Friday.
The third seed was a shadow of his brilliant self in the opening set before making the most of his Italian opponent's premature cramps to level before the bizarre match went into a decider.
Australian Open champion Sinner, who will take over as world number one next week, bowed out when he returned a massive forehand down the line wide on the third match point on court Philippe Chatrier.
Double Grand Slam champion Alcaraz, who is hoping to add to his Wimbledon and US Open titles, will face Germany's Alexander Zverev, who beat ailing seventh seed and two-time runner-up Casper Ruud of Norway 2-6, 6-2, 6-4, 6-2 in the second semi-final, on Sunday.
"You have to find the joy in suffering, I think that's the key, even more here on clay, here at Roland Garros, long rallies, four-hour matches, five sets, you have to fight, you have to suffer," said Alcaraz.
"Probably, the toughest matches that I've played in my short career have been against Jannik, the US Open 2022, this one, it shows the great player Jannik is... and I hope to play many, many more matches like this one against Jannik, but yes it's one of the toughest matches that I've played, for sure."
Sinner got off to an explosive start and his poise, pace and precision were too much to handle for an out-of-sorts Alcaraz as the Italian raced to a 4-0 lead.
The Spaniard, however, reacted and pulled a break back as Sinner's first-serve percentage took a dip.
But Alcaraz still could not find his stride and Sinner won another two games in a row to bag the opening set when his opponent netted an ill-timed drop shot.
Yet another unforced error handed Sinner the early break in the second set, but the Italian, who before the French Open had not played for almost a month because of a hip injury, suddenly lost his stride, allowing Alcaraz to use his forehand to devastating effect and level the match.
The Spaniard broke for 2-1 in the third set with a gravity-defying crosscourt passing shot as Sinner's freefall continued, but despite suffering from apparent hand cramps, the future world number one clawed his way back and saved break points in the fifth game to stay in the contest.
Sinner then broke twice more to take the set - a scenario that seemed highly unlikely when he was barely able to hold his racket a few minutes earlier.
The match finally lived up to its billing in the fourth set with both players trading impressive blows. Leading 5-4, Alcaraz rallied from 30-0 down on Sinner's serve to win four points in a row, forcing a decider with a crosscourt backhand winner at the end of a spectacular point.
He snatched the early break by wrongfooting Sinner in the second game and did not look back, despite some nerves on the first two match points.
Zverev downs ailing Ruud
Alexander Zverev wobbled early on but steadied himself to get past Casper Ruud in the second semi-final later on Friday.
The fourth seed, competing in his fourth straight Roland Garros semi-final, finally broke through to become the second German man to make the title clash in the Open Era and match Michael Stich's feat from 1996.
"I'm obviously extremely happy. I have so much history on this court, some of my best and my worst memories are on this court," said Zverev, who sustained a serious ankle ligament injury during his semi-final against Rafa Nadal in 2022.
"I'm happy to be in the final in my fourth attempt. I'm going to give it my all in the final on Sunday."
Zverev made a slow start as Ruud grabbed an early break and the first set with some clean ball-striking in front of a sparse crowd on Court Philippe Chatrier, as fans were still recovering from a four-hour epic between Alcaraz and Jannik Sinner.
Having found his range in the second set, Zverev squandered the opportunity to grab a double break with a wayward volley but the 27-year-old pulled away to level the match and broke in the fifth game of third set before extending his advantage.
The 25-year-old Ruud slowly looked like himself again after dealing with a stomach issue but his hopes of a third successive Paris final faded when Zverev struck in the Norwegian's opening service game in the fourth set and ran away with the match.
"I knew I had to be much more aggressive. The first two sets were a high level, then I saw he was struggling," Zverev said.
"Credit to him to play until the end and fight until the end. He's a great champion and person and definitely he's going to be back."
Having lost to Dominic Thiem in the 2020 US Open final, Zverev said he was ready to push for a first major title.
"I was two sets to love and a break up and two points away from winning," Zverev said of his Flushing Meadows title clash.
"But I wasn't ready to win my first Grand Slam final. I was too much of a kid. I'm 27 now, definitely not a kid anymore. If not now, then when? I'm in my first Roland Garros final and hopefully I can win my first Grand Slam."
