Polish top seed Iga Swiatek saw her 25-match winning streak on the Paris clay ended by China's Zheng Qinwen in the Olympics semi-finals.
Swiatek, 23, has won the past three French Opens at Roland Garros, but was beaten 6-2, 7-5 by sixth seed Zheng at the same venue.
Losing there for the first time since 2021 was a tough blow for the long-time world number one to take.
She was the overwhelming favourite to add Olympic gold to her five Grand Slam titles.
Swiatek was visibly upset when she tried to speak to broadcast journalists about an hour after the match and decided not to speak to written journalists - as she is entitled to do under Olympic rules.
Zheng, 21, lost in the Australian Open final earlier this year and now has a shot at earning the biggest title of her career.
The world number seven will play either Croatia's Donna Vekicor Slovakia's Anna Karolina Schmiedlova in Saturday's gold medal match.
Spanish second seed Carlos Alcaraz continued his bid to become the youngest player to win Olympic men's singles gold.
The reigning French Open and Wimbledon champion reached the semi-finals with a 6-3 7-6 (9-7) win over American ninth seed Tommy Paul.
Alcaraz, 21, will play either Norwegian sixth seed Casper Ruud or Canadian 13th seed Felix Auger-Aliassime in the last four.
