They're also two of 10 Americans in the provisional field, the most of any country.
The U.S. Tennis Association said Thursday that 100 of the top 102 in the WTA rankings are in the field. Serena Williams has won four of her 16 Grand Slam singles titles at Flushing Meadows, including last year, while Venus Williams won the tournament in 2000 and 2001.
Other past champions in the field are Maria Sharapova, Samantha Stosur and Svetlana Kuznetsova, along with two-time Australian Open winner Victoria Azarenka and recent Wimbledon champion Marion Bartoli.
The hard-court tournament begins Aug. 26, with the women's final scheduled for Sunday, Sept. 8.