2021 Geneva Open

The 2021 Geneva Open (sponsored by Gonet) was a men's tennis tournament played on outdoor clay courts. It was the 18th edition of the Geneva Open and part of the ATP Tour 250 series of the 2021 ATP Tour. It took place at the Tennis Club de Genève in Geneva, Switzerland, from May 15 through May 22, 2021.

Singles

 * 🇳🇴 Casper Ruud def. 🇨🇦 Denis Shapovalov, 7–6(8–6), 6–4

Doubles

 * 🇦🇺 John Peers / 🇳🇿 Michael Venus def. 🇮🇹 Simone Bolelli / 🇦🇷 Máximo González, 6–2, 7–5

Prize money

 * per team

Seeds

 * Rankings are as of May 10, 2021.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇧🇬 Grigor Dimitrov
 * 🇫🇷 Arthur Cazaux
 * Dominic Stricker

The following players received entry from the qualifying draw:
 * 🇮🇹 Marco Cecchinato
 * Pablo Cuevas
 * 🇧🇾 Ilya Ivashka
 * Henri Laaksonen

The following player received entry as a lucky loser:
 * 🇩🇪 Daniel Altmaier

Withdrawals

 * Before the tournament
 * 🇰🇿 Alexander Bublik → replaced by 🇺🇸 Tennys Sandgren
 * Borna Ćorić → replaced by 🇪🇸 Feliciano López
 * 🇪🇸 Alejandro Davidovich Fokina → replaced by 🇧🇷 Thiago Monteiro
 * 🇦🇺 Alex de Minaur → replaced by 🇦🇺 Jordan Thompson
 * Cristian Garín → replaced by 🇩🇪 Daniel Altmaier
 * 🇷🇸 Filip Krajinović → replaced by 🇮🇹 Salvatore Caruso
 * 🇩🇪 Jan-Lennard Struff → replaced by 🇪🇸 Fernando Verdasco

Retirements

 * 🇮🇹 Stefano Travaglia

Seeds

 * Rankings are as of May 10, 2021.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇫🇷 Arthur Cazaux / 🇨🇳 Li Hanwen
 * Marc-Andrea Hüsler / Dominic Stricker

Withdrawals

 * Before the tournament
 * 🇦🇺 Alex de Minaur / 🇦🇺 Jordan Thompson → replaced by 🇺🇸 Nathaniel Lammons / 🇺🇸 Jackson Withrow
 * Wesley Koolhof / Jean-Julien Rojer → replaced by  Marin Čilić / 🇰🇿 Andrey Golubev
 * 🇺🇸 Nicholas Monroe / 🇺🇸 Reilly Opelka → replaced by 🇺🇸 Nicholas Monroe / 🇫🇷 Benoît Paire
 * 🇺🇸 Rajeev Ram / 🇬🇧 Joe Salisbury → replaced by Pablo Cuevas / 🇦🇷 Guido Pella