Unseeded Karolina Muchova defeated second seed Aryna Sabalenka to reach the French Open final and end the Belarusian's dream of becoming world number one.
Australian Open champion Sabalenka, the overwhelming favourite to win the last-four showdown, would have taken over the top spot in the rankings by winning the title in Paris.
But she failed to convert her chance at 5-2 in the third set and bowed out to the gifted Czech 7-6(5) 6-7(5) 7-5.
The last unseeded player left in the men's and women's draw, Muchova did not attempt to match Sabalenka's massive hitting power from the baseline.
Instead the Czech, who battled back from the mid-200s into the top 50 after an injury in 2021, opted for a lighter touch.
She sliced the ball to take the pace off, playing Sabalenka's backhand and hitting drop shots to force the tall Belarusian into the net.
"I don't really know what happened," a beaming Muchova said.
"The atmosphere, the people pushing me in all the match. I just keep fighting and it worked. I really don't know what happened. I am so happy."
Muchova is only the third player ranked outside the top-40 to reach the final at Roland Garros after Jelena Ostapenko (2017) and Iga Swiatek (2020), with both of the previous two winning their respective finals.