Venus Williams reached the US Open quarter-finals for the second time in three years with a 6-3, 3-6, 6-1 victory over Carla Suarez Navarro of Spain.
The 37-year-old American is the oldest woman in the draw.
She has seven Grand Slam titles, including two in New York in 2000 and 2001.
The No. 9-seeded Williams is trying to get to her third Grand Slam final of the season.
She lost to her younger sister Serena Williams at the Australian Open and to Garbine Muguruza at Wimbledon.
Williams will meet Petra Kvitova next at Flushing Meadows. She is the only past US Open winner left in the draw.