2021 Western & Southern Open

The 2021 Western & Southern Open was a men's and women's tennis tournament played on outdoor hard courts from August 15–22, 2021, as part of the US Open Series. It was a Masters 1000 tournament on the 2021 ATP Tour and a WTA 1000 tournament on the 2021 WTA Tour.

The 2021 tournament was the 120th men's edition and the 93rd women's edition of the Cincinnati Open and took place at the Lindner Family Tennis Center in Mason, Ohio, a northern suburb of Cincinnati, in the United States, making its return to Ohio for the first time since the 2019 tournament after being held in New York City for 2020 due to the COVID-19 pandemic in the United States. It operated at full spectator capacity as participants were required to have tested negative for COVID-19 or be fully vaccinated.

Men's singles

 * 🇩🇪 Alexander Zverev def. 🇷🇺 Andrey Rublev, 6–2, 6–3

Women's singles

 * 🇦🇺 Ashleigh Barty def. Jil Teichmann, 6–3, 6–1

This was Barty's 13th WTA singles title, and fifth of the year.

Men's doubles

 * 🇪🇸 Marcel Granollers / 🇦🇷 Horacio Zeballos def. 🇺🇸 Steve Johnson / 🇺🇸 Austin Krajicek, 7–6(7–5), 7–6(7–5)

Women's doubles

 * 🇦🇺 Samantha Stosur / 🇨🇳 Zhang Shuai def. 🇨🇦 Gabriela Dabrowski / 🇧🇷 Luisa Stefani, 7–5, 6–3

Seeds
The following were the seeded players. Seedings were based on ATP rankings as of August 9, 2021. Rank and points before were as of August 16, 2021.

For the first time since the ATP Tour resumed from its pandemic suspension in August 2020, ATP rankings points were added and dropped per traditional methodology beginning 23 August 2021 (the rankings after the 2021 Western & Southern Open in Cincinnati). A player's current Western & Southern Open ATP ranking points (the greater from 2019 and 2020) dropped 23 August 2021 and were replaced with points earned by the player at this year's Western & Southern Open. Those new points would stay on a player's breakdown for 52 weeks, dropping 22 August 2022. Players who had Western & Southern Open points in their breakdown and did not compete in this year's event also had their existing Cincinnati ranking points drop on 23 August 2021.

† The player is also defending points from the 2019 Winston-Salem Open, which was played during this calendar week in 2019.

‡ The player did not qualify for the tournament in 2019 or 2020. Accordingly, points for his 19th best result are deducted instead.

^ Because the 2021 tournament was non-mandatory, the player substituted his 19th best result in place of the points won in this tournament.

Other entrants
The following players received wild cards into the main singles draw:
 * 🇺🇸 Mackenzie McDonald
 * 🇬🇧 Andy Murray
 * 🇺🇸 Brandon Nakashima
 * 🇺🇸 Frances Tiafoe

The following player received entry using a protected ranking into the main singles draw:
 * 🇦🇷 Guido Pella

The following players received entry from the singles qualifying draw:
 * 🇪🇸 Carlos Alcaraz
 * Kevin Anderson
 * 🇫🇷 Richard Gasquet
 * 🇺🇸 Marcos Giron
 * 🇫🇷 Corentin Moutet
 * 🇯🇵 Yoshihito Nishioka
 * 🇺🇸 Tommy Paul

The following player received entry as a lucky loser:
 * 🇩🇪 Dominik Koepfer

Withdrawals

 * Before the tournament
 * Borna Ćorić → replaced by 🇺🇸 Sebastian Korda
 * 🇷🇸 Novak Djokovic → replaced by 🇩🇪 Jan-Lennard Struff
 * Roger Federer → replaced by 🇦🇷 Federico Delbonis
 * 🇫🇷 Adrian Mannarino → replaced by 🇷🇸 Miomir Kecmanović
 * 🇦🇺 John Millman → replaced by 🇩🇪 Dominik Koepfer
 * 🇪🇸 Rafael Nadal → replaced by 🇦🇷 Guido Pella
 * 🇯🇵 Kei Nishikori → replaced by 🇷🇸 Laslo Đere
 * 🇨🇦 Milos Raonic → replaced by 🇫🇷 Benoît Paire
 * 🇦🇹 Dominic Thiem → replaced by 🇩🇪 Dominik Koepfer
 * Stan Wawrinka → replaced by 🇷🇸 Dušan Lajović

Seeds

 * Rankings are as of August 9, 2021.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇺🇸 Steve Johnson / 🇺🇸 Austin Krajicek
 * 🇺🇸 Nicholas Monroe / 🇺🇸 Frances Tiafoe
 * 🇨🇦 Denis Shapovalov / 🇺🇸 Jack Sock

The following pairs received entry as an alternates:
 * Marcelo Arévalo / 🇮🇹 Fabio Fognini
 * 🇷🇺 Aslan Karatsev / 🇷🇸 Dušan Lajović

Withdrawals

 * Before the tournament
 * Wesley Koolhof / Jean-Julien Rojer → replaced by  Wesley Koolhof / 🇩🇪 Jan-Lennard Struff
 * 🇫🇷 Nicolas Mahut / 🇫🇷 Fabrice Martin → replaced by 🇷🇸 Filip Krajinović / 🇫🇷 Fabrice Martin
 * 🇬🇧 Jamie Murray / 🇦🇺 Max Purcell → replaced by 🇷🇺 Aslan Karatsev / 🇷🇸 Dušan Lajović
 * 🇨🇦 Denis Shapovalov / 🇺🇸 Jack Sock → replaced by Marcelo Arévalo / 🇮🇹 Fabio Fognini

Seeds

 * 1 Rankings are as of August 9, 2021

Other entrants
The following players received wild cards into the main singles draw:
 * 🇺🇸 Caty McNally
 * 🇺🇸 Bernarda Pera
 * 🇺🇸 Sloane Stephens
 * 🇦🇺 Samantha Stosur
 * Jil Teichmann

The following player received entry using a special exempt into the main singles draw:
 * 🇮🇹 Camila Giorgi

The following players received entry from the singles qualifying draw:
 * 🇨🇦 Leylah Annie Fernandez
 * 🇫🇷 Caroline Garcia
 * Hsieh Su-wei
 * 🇮🇹 Jasmine Paolini
 * 🇷🇺 Liudmila Samsonova
 * 🇧🇾 Aliaksandra Sasnovich
 * 🇬🇧 Heather Watson
 * 🇨🇳 Zhang Shuai

The following player received entry as a lucky loser:
 * 🇸🇪 Rebecca Peterson

Withdrawals

 * Before the tournament
 * 🇺🇸 Sofia Kenin → replaced by 🇵🇱 Magda Linette
 * 🇷🇺 Anastasia Pavlyuchenkova → replaced by 🇸🇪 Rebecca Peterson
 * 🇺🇸 Serena Williams → replaced by 🇺🇦 Dayana Yastremska


 * During the tournament
 * 🇷🇴 Simona Halep (right adductor injury)

Retirements

 * 🇪🇸 Paula Badosa (right shoulder injury)
 * 🇺🇸 Jennifer Brady (right knee injury)
 * 🇺🇸 Danielle Collins (exhaustion)
 * 🇨🇿 Petra Kvitová (stomach issue)
 * 🇨🇿 Karolína Muchová (abdominal injury)

Seeds

 * Rankings are as of August 9, 2021.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇵🇱 Magda Linette / 🇺🇸 Bernarda Pera
 * 🇺🇸 Emma Navarro / 🇺🇸 Peyton Stearns

The following pairs received entry using protected rankings:
 * 🇰🇿 Anna Danilina / 🇰🇿 Yaroslava Shvedova
 * 🇹🇳 Ons Jabeur / 🇮🇳 Sania Mirza
 * 🇰🇿 Galina Voskoboeva / 🇷🇺 Vera Zvonareva

Withdrawals

 * Before the tournament
 * 🇺🇸 Sofia Kenin / Jeļena Ostapenko → replaced by  Jeļena Ostapenko /  Jil Teichmann
 * 🇷🇺 Veronika Kudermetova / 🇷🇺 Elena Vesnina → replaced by 🇷🇺 Anna Blinkova / 🇧🇾 Aliaksandra Sasnovich

Prize money

 * per team