Williams had twice won 21 in a row before, although both of those streaks came a decade ago, in 2002 and 2003.
Martina Navratilova established the longest women's win streak in the Open Era at 74 matches in 1984.
"I've been pretty consistent, and pretty healthy knock on wood," Williams said. "I feel great never felt better."
In the other half of the draw, two-time defending champion Maria Sharapova withdrew before her quarterfinal match against seventh-seeded Sara Errani due to illness.
In men's play, 36th-ranked Benoit Paire of France cruised past Marcel Granollers of Spain 6-1, 6-0 to reach his first Masters series semifinal. His next opponent will be either 17-time Grand Slam winner Roger Federer or rising Polish player Jerzy Janowicz, who were playing in a night match.