The Polish crowd was left disappointed as home favourite Agnieszka Radwanska was beaten 0-6 6-2 6-4 by Alize Cornet in the semi-finals of the Katowice Open.
World No 3 Radwanska raced through the opening set without dropping a game before losing her way, and despite starting the decider strongly she faltered again.
For Cornet, who will play Camila Giorgi in the final, it was a remarkable victory given both her slow start and the fact she dropped the opening three games of the third set.
She had turned the momentum of the match at the start of the second set by stealing successive breaks of serve to lead 4-0, and held her nerve to close that one out and level the contest.
Radwanska looked to have overcome the disappointment of losing the middle set but her level fell as Cornet responded to the challenge to secure her first win in four matches against the 2012 Wimbledon runner-up.
Cornet will contest her eighth WTA career final on Sunday, seeking a fourth title.
Giorgi, meanwhile, will be playing in her maiden final at the WTA Tour level after the 22-year-old Italian knocked out third seed Carla Suarez Navarro with a 7-6 (7-2) 6-4 success.
"It was a tough match,” Giorgi told the WTA’s official website.
“It wasn't easy. I wasn't playing really well, and neither of us were that consistent today, but I tried my best and I think I was just a little bit better in the end. I played well on the important points today."