Dutch teenager Michaella Krajicek saved one match-point to upset top-seeded Elena Dementieva 1-6, 7-6 (5), 6-4 and move into the Ordina Open final.
The 17-year-old Krajicek will play today against Dinara Safina, who beat 2002 winner Eleni Daniilidou of Greece 6-3, 3-6, 6-4.
"I can't believe I have won," Krajicek said. "This was the best match of my career."
On the men's side, defending champion Mario Ancic of Croatia reached the final by beating Marcos Baghdatis of Cyprus 7-6 (4), 6-3.
Ancic, defending his only ATP title, will meet Jan Hernych of the Czech Republic, who defeated Florent Serra of France 6-2, 7-6 (3) at the Netherlands' only grass-court event.
After racing through the first set, Dementieva was in disbelief in the second when serving on match-point a shot by Krajicek was called in. Krajicek went on to force a tie-breaker to take the set.
She then broke Dementieva in the 10th game to win the decider.
Dementieva said the linesman's decision had left her "disappointed."
"It has never happened to me before. It has to be fair play," she said.
The Ordina Open hasn't been won by a Dutchwoman since the women's event was introduced in 1996.