Serena Williams, the top seed, came back from a set down in her Roland Garros quarterfinal against the Russian Svetlana Kuznetsova, to win 6-1, 3-6, 6-3.
The Italian Sara Errani, the No. 5 seed, beat Agnieszka Radwanska of Poland, the No. 4 seed, 6-4, 7-6(6) to advance to the semifinals.
Williams and Errani will face off on Thursday to determine who will be in the final.