The 2021 St. Petersburg Open was a tennis tournament played on indoor hard courts.

It was the 26th edition of the St. Petersburg Open, and part of the ATP World Tour 250 Series of the 2021 ATP Tour.

It took place at the Sibur Arena in Saint Petersburg, Russia, from October 25 through 31, 2021.

Taylor Fritz, 7–6(7–3), 4–6, 6–4 Jamie Murray / Bruno Soares def.

Andrey Golubev / Hugo Nys, 6–3, 6–4 The following players received wildcards into the singles main draw: The following player received entry using a protected ranking: The following players received entry from the qualifying draw: The following pairs received wildcards into the doubles main draw: