Paris - Stan Wawrinka became the oldest French Open finalist in 44 years on Friday with an epic 6-7 (6/8), 6-3, 5-7, 7-6 (7/3), 6-1 win over world number one Andy Murray.
The 2015 champion will face nine-time winner Rafael Nadal, who thrashed Dominic Thiem 6-3, 6-4, 6-0, for the title after avenging his loss to Murray at the same stage in Paris last year.
US Open champion Wawrinka, 32, triumphed in a pulsating four-hour 34-minute battle of shotmaking and endurance and will target a fourth Slam title on Sunday.
His win atoned for defeat to Murray in the semi-finals a year ago and the Swiss suggested that the Briton was nowhere near that form on Friday.
"Last year he was much more aggressive but last year he was stronger," said Wawrinka after reaching his fourth final at the majors.
"Today I think he's less confident. He played a bit less fast. He was a little more hesitant, and that gave me a bit more time to actually install my game.
"You know, when you start hesitating, you don't necessarily make the right picks," added Wawrinka, the oldest finalist in Paris since 33-year-old Niki Pilic was runner-up in 1973.
For Murray, his wait to become Britain's first men's champion in Paris since Fred Perry in 1935 goes on.
The 30-year-old admitted that Wawrinka was the stronger of the two.
"I tried to keep fighting, but he played well at the end," said Murray, the 2016 runner-up to Novak Djokovic.
"I was a tiebreak from getting to the final in a tournament which I came into struggling. So I can be proud of what I have done."
Wawrinka broke for a 5-3 lead in the opener but handed the advantage straight back to the Scot in his next service game.
In a gripping tiebreak, an instinctive, point-blank backhand volley gave the Swiss a set point.
Again he was unable to take advantage and it was Murray who pounced for the opening set after 71 minutes when his opponent netted a backhand return off a second serve.
Murray only notched nine winners in the set but Wawrinka's 23 unforced errors proved his undoing as he shipped his first set of the tournament.
However, Wawrinka quickly hit back, breaking first again for 4-3 in the second set and again in the ninth game to level the semi-final, running around a second serve to bury a forehand winner.
Wawrinka raced into a 3-0 lead in the third before Murray halted a seven-game losing streak and retrieved the break in the fifth game.
A further break apiece followed before Murray, with his trademark defensive skills in overdrive, edged back in front for 6-5 followed by the set-clinching hold.
The pair had already been on court for three hours.
Solid serving, counter-punching and stunning attack by both men sent the fourth set to a tiebreak without a single break point given up.
Wawrinka took it to level the semi-final after four hours, another laser forehand speeding past Murray.
The US Open champion was now in the ascendancy, breaking in the first game of the decider and backing it with a comfortable hold.
An astonishing triple break took him to 5-0 and although Murray clawed one back, the marathon battle - the longest of the tournament - had taken its toll.
Wawrinka booked his place in his fourth Slam final with another stylish backhand down the line winner.
The Swiss, who has won all his three Slam finals, ended with 87 winners and 77 unforced errors.
Murray had 36 of each.