(CNN) -- Samantha Stosur of Australia inflicted Justine Henin's first French Open defeat since 2004 to set up a quarterfinal against Serena Williams.
Stosur, the seventh seed who reached the semifinals at Roland Garros last year, rallied after losing the first set to stun the Belgian with a 2-6 6-1 6-4 victory.
Henin has been looking to regain the title she won four years in a row before taking a break from the game in 2008.
"Of course it's disappointing," Henin told reporters. "It's never easy to lose, especially in this kind of situation. I just wanted so much to let the adventure keep going.
"I haven't been at my best today and Samantha was the best player on the court. She took her chances."
Top seed Williams was at her imperious best in easily defeating Shahar Peer of Israel 6-2 6-2.
The American surprisingly lost the first seven points of the match on a cold, windy day, but rebounded to win the next nine and took the first set 6-2
The second set was a tight affair before Williams went up a gear and won the last three games to take the match.
"I felt really powerful today and strong and able to dictate," Williams said.
"Even though sometimes she put me on the run, I felt like I was able to still be on the offence.
Jelena Jankovic of Serbia will meet Kazakhstan's Yarolslava Shvedova in the last eight after both won their last 16 matches.
Jankovic beat Slovakia's Daniele Hantuchova 6-4 6-2, while Shvedova defeated Jarmila Groth of Australia 6-4 6-3.