Australian Samantha Stosur pulled off a stunning 6-2, 6-7, 8-6 victory over top seed Serena Williams on Wednesday to reach the semi-finals of the French Open for the second year in succession.

Williams recovered had a match point at 5-4 in the third set of see-sawing contest but seventh seed Stosur battled back to clinch a dramatic victory and set up a last-four clash with fourth seed Jelena Jankovic of Serbia.

Stosur used her fierce forehand to force a succession of errors from the world number one, breaking twice to take the opening set and surge ahead 5-3 in the second.

Stosur had earlier, in the fourth round, accounted for four-time champion Justine Henin of Belgium.

Williams slowly found her range and broke back and after taking the tiebreak 7-2 she looked set for victory when Stosur wavered when serving to stay in the match in the 10th game of a tense deciding set.

Williams just missed a forehand pass on her only match point and was broken in the next game before Stosur held serve to wrap up victory after two hours and 24 minutes.

Williams won the Roland Garros title in 2002 but has largely struggled to assert her authority on the red clay of Paris.

Jelena Jankovic reached the French Open semi-finals for the third time in her career on Wednesday with a 7-5, 6-4 defeat of Kazakhstan's Yaroslava Shvedova.

The fourth seed was given a tough time by the world number 36 but enjoyed some unlikely assistance from her opponent near the end of the one hour 31 minute contest.

Shvedova, who wore sunglasses, completely missed an easy smash to hand Jankovic a break of serve and level the second set at 4-4 and then served a double fault on match point down.

Serbia's Jankovic will face Samantha Stosur of Australia in the last four.