2021 Geneva Open – Singles

Alexander Zverev was the defending champion from when the event was held in 2019, but chose not to defend his title.

Casper Ruud won the title, defeating Denis Shapovalov in the final, 7–6(8–6), 6–4.

Seeds
The top four seeds received a bye into the second round. • # Roger Federer (second round)

• #🇨🇦 Denis Shapovalov (final)

• #🇳🇴 Casper Ruud (champion)

• #🇧🇬 Grigor Dimitrov (quarterfinals)

• # Cristian Garín (withdrew)

• #🇮🇹 Fabio Fognini (second round)

• #🇫🇷 Benoît Paire (first round)

• #🇫🇷 Adrian Mannarino (first round)

Seeds
• # 🇧🇾 Ilya Ivashka (qualified)

• # 🇮🇹 Marco Cecchinato (qualified)

• # 🇰🇿 Mikhail Kukushkin (first round)

• # Pablo Cuevas (qualified)

• # 🇺🇸 Mackenzie McDonald (qualifying competition)

• # 🇩🇪 Peter Gojowczyk (first round)

• # 🇩🇪 Cedrik-Marcel Stebe (first round)

• # 🇩🇪 Daniel Altmaier (qualifying competition, lucky loser)

Qualifiers
• # 🇧🇾 Ilya Ivashka

• # 🇮🇹 Marco Cecchinato

• # Henri Laaksonen

• # Pablo Cuevas

Lucky loser

 * 1) 🇩🇪 Daniel Altmaier