2021 Swiss Open Gstaad – Singles
| Singles | |
|---|---|
| 2021 Swiss Open Gstaad | |
| Champion | Casper Ruud |
| Runner-up | Hugo Gaston |
| Score | 6–3, 6–2 |
| Draw | 28 (4 Q / 3 WC ) |
| Seeds | 8 |
Casper Ruud defeated Hugo Gaston in the final, 6–3, 6–2, to win the men's singles tennis title at the 2021 Swiss Open.
Albert Ramos Viñolas was the reigning champion from when the tournament was last held in 2019, but chose to compete in Umag instead.