2021 Kremlin Cup

• Aslan Karatsev def. Marin Čilić, 6–2, 6–4

• Anett Kontaveit def. Ekaterina Alexandrova, 4–6, 6–4, 7–5.

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

• Harri Heliövaara / Matwé Middelkoop def. Tomislav Brkić / Nikola Ćaćić, 7–5, 4–6, [11–9]

• Jeļena Ostapenko / Kateřina Siniaková def. Nadiia Kichenok / Raluca Olaru, 6–2, 4–6, [10–8]

Country	Player	Rank1	Seed
RUS	Andrey Rublev	5	1
RUS	Aslan Karatsev	23	2
RUS	Karen Khachanov	29	3
KAZ	Alexander Bublik	34	4
SRB	Filip Krajinović	37	5
CRO	Marin Čilić	41	6
BLR	Ilya Ivashka	45	7
SRB	Laslo Đere	47	8

• Rankings are as of October 4, 2021

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

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

Country	Player	Country	Player	Rank1	Seed
RSA	Raven Klaasen	JPN	Ben McLachlan	57	1
KAZ	Andrey Golubev	MON	Hugo Nys	94	2
AUS	Luke Saville	AUS	John-Patrick Smith	96	3
BIH	Tomislav Brkić	SRB	Nikola Ćaćić	97	4

• ¹ Rankings are as of October 4, 2021

The following pairs received wildcards into the doubles main draw:

• Aslan Karatsev / Richard Muzaev
• Pavel Kotov / Roman Safiullin

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

Country	Player	Rank1	Seed
BLR	Aryna Sabalenka	2	1
ESP	Garbiñe Muguruza	6	2
GRE	Maria Sakkari	9	3
RUS	Anastasia Pavlyuchenkova	13	4
TUN	Ons Jabeur	14	5
GER	Angelique Kerber	15	6
KAZ	Elena Rybakina	16	7
ROU	Simona Halep	17	8
EST	Anett Kontaveit	20	9

• Rankings are as of October 4, 2021 .[4]

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

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

Country	Player	Country	Player	Rank1	Seed
CHI	Alexa Guarachi	USA	Desirae Krawczyk	29	1
LAT	Jeļena Ostapenko	CZE	Kateřina Siniaková	35	2
CZE	Marie Bouzková	CZE	Lucie Hradecká	70	3
UKR	Nadiia Kichenok	ROU	Raluca Olaru	72	4

• ¹ Rankings are as of October 4, 2021

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

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