Barbora Krejcikova has become the first Czech woman in 40 years to reach the French Open final, as she beat Greek 17th seed Maria Sakkari 7-5 4-6 9-7 in a nail-biting, see-saw contest on Friday (NZ time).
The world No. 33 struggled with nerves throughout but eventually proved more consistent than Sakkari, who got tight when she served for the match at 5-4 in the third set.
Krejcikova will face Russian 31st seed Anastasia Pavlyuchenkova, who will also be making her maiden appearance in a major singles final.
"When I was young, a junior, I wanted to play matches like this, such challenging matches," says Krejcikova.
"Even if I had lost today, I would have been proud of myself. I was just fighting, that's the most important."
With both Sakkari and Krejcikova playing in their first Grand Slam semi-final, the match got off to a shaky start.
Sakkari was the first to hold serve on a sunbaked court Philippe Chatrier to open a 3-1 lead but her advantage was shortlived.
Krejcikova, who came into the semi-final on a 10-match winning streak after claiming the title in Strasbourg last month, rallied back as Sakkari lost her way in the sixth game.
Krejcikova then broke for 5-3 with a superb lob as she retrieved a drop shot, but dropped serve straight after with a double fault on game point.
She sealed the opening set with yet another break, however, when Sakkari's crosscourt forehand went wide after clipping the net cord.
Sakkari raced to a 4-0 lead in the second set but Krejcikova cancelled out one of the two breaks of serve to narrow the deficit to 3-4, only for the Greek to serve it out, letting out a huge scream out as she sent the contest into a decider.
Sakkari broke in the first game and managed to hold after conceding five breaks of serve in the first two sets.
Krejcikova saved a match point on her serve at 3-5, forcing Sakkari to serve for the match.
The Greek fell 0-30 behind after two unforced errors before saving a break point with a sizzling crosscourt backhand winner.
She was broken, however, when she sent a backhand into the net to allow Krejcikova to level for 5-5.
Serving at 6-7, Sakkari saved three match points. Krejcikova thought she had it in the bag on her fourth match point at 7-8 when Sakkari's forehand was called long, only for the chair umpire to rule it was in.
On the fifth, however, Krejcikova ended the contest with a backhand winner after three hours and 18 minutes.
Earlier, Pavlyuchenkova has held steady to beat an erratic Tamara Zidansek in straight sets to reach the final at her 52nd Grand Slam tournament.
The 29-year-old's 7-5 6-3 win made her the woman with the most attempts ever needed to reach the final of one of the four majors.
It was a reward for her patience throughout a career that has earned her 12 titles but none on the biggest of stages, and also for her calmness against a player who blew hot and cold.
Pavlyuchenkova, the oldest of the four first-time semi-finalists here, will play 17th seed Maria Sakkari of Greece or the unseeded Czech Barbora Krejcikova in Saturday's final.
"I am so tired and so happy, it is very emotional," Pavlyuchenkova says.
"It was difficult, I tried to fight very hard and to work on the tactical side. It is important to stay focused and in the right zone for the final."
While 31st seed Pavlyuchenkova had reached the quarter-finals at six Grand Slams, Zidansek had only managed three match wins at Grand Slams before arriving in Paris.
Her destructive forehand worked well initially and she broke Pavlyuchenkova's opening service game before holding to love. But she missed a smash at 2-1 as Pavlyuchenkova got back on level terms and the Russian then broke for a 5-3 lead.
Zidansek produced an incredible improvised lob volley and some crunching forehand winners to break back and was 15-40, when Pavlyuchenkova served at 5-5 but could not convert the chance.
Pavlyuchenkova absorbed Zidansek's best shots and was gifted the first set with a double-fault.
The Russian forged 4-1 ahead in the second set and snuffed out an attempted Zidansek comeback, clinching victory when her opponent blazed a backhand wide, her 33rd unforced error.
There was little by way of celebration for Pavlyuchenkova, who looked relieved more than anything, as she became the first Russian woman to reach a Grand Slam final since Maria Sharapova lost to Serena Williams at the 2015 Australian Open.
She also surpassed Roberta Vinci, who took 44 Grand Slam attempts before reaching the 2015 US Open final.