Serena Williams's quest for a record-equalling 24th Grand Slam singles title was put on hold on Saturday after the former world number one was knocked out of the French Open in the third round following a 6-2 7-5 defeat by fellow American Sofia Kenin.
Chasing Margaret Smith Court's all-time record, which was built over the amateur and professional eras, Williams failed to recover from a woeful opening set on Court Philippe Chatrier.
In the players' first meeting, world number 35 Kenin pulled Williams around the court and made the most of her opponent's unforced errors to set up a last-16 encounter with Australian eighth seed Ashleigh Barty.
Williams, who won the last of her 23 major singles titles at the 2017 Australian Open, suffered her earliest Grand Slam exit since Wimbledon 2014.
"It's a lot of emotion, she's such a great player, a true champion, so much respect for her," said Kenin, who was booed by a fraction of the crowd while Williams left the court to a standing ovation.
"Playing against Serena, you've got to fight for every point, she's such tough player, I'm so happy with this win."
Kenin, who won her maiden singles WTA title this season in Hobart, made the most of Williams's shaky start, breaking for 3-2 as the 10th seed sprayed the court with unforced errors.
Williams's forehand was woeful and her opponent piled on the pressure to move 5-2 up with another break.
Serving for the set, Kenin thought she had bagged it when Williams returned long, only for the umpire to rule her serve out.
Kenin smacked the netcord with her racket in frustration, drawing jeers from the Paris crowd, before regaining her composure and wrapping it on her second opportunity.
Williams was broken to love in the first game of the second set and looked nothing close to finding a solution against Kenin's pace.
She screamed her lungs out after winning the first two points of the following game, but Kenin was not impressed and snatched her seventh consecutive game.
Williams was hitting short, however, allowing Kenin to step into the court and dictate play. But in the sixth game, Williams finally broke to level for 3-3 as Kenin showed more signs of nerves, disputing several calls from the umpire or the linesmen.
It was her way to stay in the game, however, and she claimed the decisive break for 6-5 with a lighting-quick service return that left Williams stranded.
Kenin missed a forehand on her first match point, and it was Williams who handed her the win when she sent a backhand long, filling the youngster's eyes with tears.