2021 St. Petersburg Ladies' Trophy – Singles
| Singles | |
|---|---|
| 2021 St. Petersburg Ladies' Trophy | |
| Champion | Daria Kasatkina |
| Runner-up | Margarita Gasparyan |
| Score | 6–3, 2–1, ret. |
| Draw | 28 (6 Q / 4 WC ) |
| Seeds | 8 |
Daria Kasatkina won the women's singles title at the 2021 St. Petersburg Ladies' Trophy, after Margarita Gasparyan retired from the final with the scoreline at 6–3, 2–1.
Kiki Bertens was the two-time defending champion, but she chose not to participate.
This was the first tournament since Oakland in 1993 in which seven of the eight quarterfinalists were all from the same country. It was also the first tournament in WTA history in which all four semifinalists represented Russia.