Anastasia Pavlyuchenkova will play her first Grand Slam final at Roland Garros.
The 31st-seeded player defeated unseeded Tamara Zidansek 7-5; 6-3 to become the first Russian woman to reach a final at a major since Maria Sharapova at the 2015 Australian Open.
Both players struggled with their serves on Court Philippe Chatrier but Pavlyuchenkova managed to hold her nerves better on important points.
Zidansek, who had never been beyond the second round at a major before; hit some superb drop shots and forehand winners but also made 33 unforced errors.
“I wanted this so much that right now I don’t feel anything,” Pavlyuchenkova said.
“Tennis is such a mental sport. That’s what is really hard about tennis.”
None of the four women’s semifinalists had previously advanced so far at a Grand Slam tournament.
Pavlyuchenkova will either 17th-seeded Maria Sakkari or Barbora Krejcikova in Saturday’s final.