2021 Kremlin Cup

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. It was the 31st edition of the Kremlin Cup for the men and the 25th edition for the women. The tournament was part of the ATP 250 series of the 2021 ATP Tour, and of the WTA 500 series of the 2021 WTA Tour. 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.

Men's singles

 * 🇷🇺 Aslan Karatsev def. Marin Čilić, 6–2, 6–4

Women's singles

 * 🇪🇪 Anett Kontaveit def. 🇷🇺 Ekaterina Alexandrova, 4–6, 6–4, 7–5.

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

Men's doubles

 * 🇫🇮 Harri Heliövaara / Matwé Middelkoop def. 🇧🇦 Tomislav Brkić / 🇷🇸 Nikola Ćaćić, 7–5, 4–6, [11–9]

Women's doubles

 * Jeļena Ostapenko / 🇨🇿 Kateřina Siniaková def. 🇺🇦 Nadiia Kichenok / 🇷🇴 Raluca Olaru, 6–2, 4–6, [10–8]

Seeds

 * Rankings are as of October 4, 2021

Other entrants
The following players received wildcards into the singles main draw:
 * 🇷🇺 Evgeny Donskoy
 * 🇷🇺 Alibek Kachmazov
 * 🇷🇺 Roman Safiullin

The following players received entry using a protected ranking:
 * 🇦🇷 Guido Pella
 * 🇫🇷 Gilles Simon

The following players received entry from the qualifying draw:
 * 🇧🇦 Damir Džumhur
 * 🇧🇾 Egor Gerasimov
 * Borna Gojo
 * 🇺🇦 Illya Marchenko

The following player received entry as a lucky loser:
 * 🇱🇹 Ričardas Berankis

Withdrawals

 * Before the tournament
 * 🇪🇸 Pablo Andújar → replaced by 🇦🇷 Federico Coria
 * 🇧🇾 Ilya Ivashka → replaced by 🇱🇹 Ričardas Berankis
 * 🇺🇸 Sebastian Korda → replaced by 🇫🇷 Gilles Simon
 * 🇷🇺 Daniil Medvedev → replaced by 🇸🇪 Mikael Ymer

Seeds

 * 1 Rankings are as of October 4, 2021

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇷🇺 Aslan Karatsev / 🇷🇺 Richard Muzaev
 * 🇷🇺 Pavel Kotov / 🇷🇺 Roman Safiullin

Withdrawals

 * Before the tournament
 * 🇪🇸 Pablo Andújar / 🇷🇸 Laslo Đere → replaced by 🇷🇸 Laslo Đere / 🇦🇷 Guido Pella
 * Marcelo Arévalo / Matwé Middelkoop → replaced by 🇫🇮 Harri Heliövaara /  Matwé Middelkoop
 * Marin Čilić / 🇺🇸 Sebastian Korda → replaced by 🇧🇾 Ilya Ivashka / 🇪🇸 Pedro Martínez

Seeds

 * Rankings are as of October 4, 2021.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇷🇴 Simona Halep
 * 🇪🇪 Anett Kontaveit
 * 🇷🇺 Anastasia Potapova
 * 🇧🇾 Aryna Sabalenka

The following players received entry from the qualifying draw:
 * 🇷🇺 Anna Kalinskaya
 * 🇷🇸 Aleksandra Krunić
 * 🇺🇸 Bernarda Pera
 * 🇷🇺 Oksana Selekhmeteva
 * 🇺🇦 Lesia Tsurenko
 * 🇨🇳 Zheng Qinwen

The following player received entry as a lucky loser:
 * 🇷🇴 Irina Bara

Withdrawals

 * Before the tournament
 * 🇨🇦 Bianca Andreescu → replaced by 🇺🇦 Anhelina Kalinina
 * 🇪🇸 Paula Badosa → replaced by 🇩🇪 Andrea Petkovic
 * Belinda Bencic → replaced by 🇺🇦 Dayana Yastremska
 * 🇺🇸 Danielle Collins → replaced by 🇨🇿 Markéta Vondroušová
 * 🇩🇪 Angelique Kerber → replaced by 🇷🇴 Irina Bara
 * Petra Martić → replaced by 🇨🇿 Kateřina Siniaková
 * 🇧🇪 Elise Mertens → replaced by 🇷🇺 Liudmila Samsonova
 * 🇬🇧 Emma Raducanu → replaced by 🇨🇿 Tereza Martincová

Seeds

 * 1 Rankings are as of October 4, 2021

Other entrants
The following pair received a wildcard into the doubles main draw:
 * 🇷🇺 Oksana Selekhmeteva / 🇷🇺 Anastasia Tikhonova

The following pair received entry using a protected ranking:
 * 🇧🇾 Vera Lapko / 🇧🇾 Lidziya Marozava

Withdrawals

 * Before the tournament
 * 🇨🇦 Sharon Fichman / 🇲🇽 Giuliana Olmos → replaced by 🇷🇺 Anna Kalinskaya / 🇷🇺 Anastasia Potapova
 * 🇷🇺 Veronika Kudermetova / 🇷🇺 Elena Vesnina → replaced by 🇷🇺 Natela Dzalamidze / 🇷🇺 Kamilla Rakhimova
 * 🇦🇺 Arina Rodionova / 🇧🇾 Aliaksandra Sasnovich → replaced by 🇰🇿 Anna Danilina / 🇦🇺 Arina Rodionova
 * 🇷🇴 Monica Niculescu / 🇷🇴 Elena-Gabriela Ruse → replaced by 🇧🇾 Vera Lapko / 🇧🇾 Lidziya Marozava