The 2021 Kremlin Cup (also known as the 2021 VTB Kremlin Cup for sponsorship reasons) was a professional tennis tournament played on indoor hard courts.

The tournament was part of the ATP 250 series of the 2021 ATP Tour,[1] and of the WTA 500 series of the 2021 WTA Tour.

[2] It was held at the Irina Viner-Usmanova Gymnastics Palace and the Luzhniki Palace of Sports in Moscow, Russia, from 18 October through 24 October 2021.

[3] This was Kontaveit's 4th WTA title, and 3rd of the year.

The following players received wildcards into the singles main draw: The following players received entry using a protected ranking: The following players received entry from the qualifying draw: The following player received entry as a lucky loser: The following pairs received wildcards into the doubles main draw: The following players received wildcards into the singles main draw: The following players received entry from the qualifying draw: The following player received entry as a lucky loser: The following pair received a wildcard into the doubles main draw: The following pair received entry using a protected ranking: