Williams won the first four games and final 10 points Sunday and easily took a 6-1, 6-3 decision from 15th-seeded Roberta Vinci. Williams improved to 40-2 on the year. The 28-match winning streak is a career best.
She opened the match with two unforced errors but still ended up with a break en route to a 4-0 lead and closed out the set with her third break of the day.
Vinci held at love to get to 3-3 of the second set but Williams, who only had to deal with one break point on the day, held. She won the last two points in that game and broke at love and served out a four-point game to end the match in 68 minutes.
Williams, who has lost just 10 games over her first four matches in Paris, heads into the quarterfinals against Svetlana Kuznetsova, who eliminated eighth-seeded Angelique Kerber 6-4, 4-6, 6-3 earlier Sunday. Kuznetsova claimed her third Grand Slam quarterfinal since she won the 2009 French Open with a pair of third-set breaks.
Kuznetsova beat Williams in three sets in the quarterfinals in Paris in 2009 but Williams has won six of their eight previous meetings.