2021 Swiss Open Gstaad
The 2021 Swiss Open Gstaad was a men's tennis tournament played on outdoor clay courts. It was the 53rd edition of the Swiss Open, and part of the ATP Tour 250 Series of the 2021 ATP Tour. It took place at the Roy Emerson Arena in Gstaad, Switzerland, from 19 July through 25 July 2021.
Champions
Singles
Casper Ruud def. Hugo Gaston, 6–3, 6–2Doubles
Marc-Andrea Hüsler / Dominic Stricker def. Szymon Walków / Jan Zieliński, 6–1, 7–6Points and prize money
Prize money
| Event | W | F | SF | QF | Round of 16 | Round of 32 | Q2 | Q1 |
| Singles | €41,145 | €29,500 | €21,000 | €14,000 | €9,000 | €5,415 | €2,645 | €1,375 |
| Doubles* | €15,360 | €11,000 | €7,250 | €4,710 | €2,760 |
*per team
Singles main draw entrants
Seeds
1 Rankings are as of July 12, 2021Other entrants
The following players received wildcards into the main draw:The following players received entry from the qualifying draw:
The following players received entry as lucky losers:
Withdrawals
;Before the tournament- Facundo Bagnis → replaced by Juan Ignacio Londero
- Roberto Carballés Baena → replaced by Tallon Griekspoor
- Federico Coria → replaced by Hugo Gaston
- Norbert Gombos → replaced by Dennis Novak
- Yannick Hanfmann → replaced by Kacper Żuk
- Philipp Kohlschreiber → replaced by Enzo Couacaud
- Kamil Majchrzak → replaced by Marc-Andrea Hüsler
- Dominic Thiem → replaced by Arthur Rinderknech
- Jo-Wilfried Tsonga → replaced by Marc Polmans
- Fernando Verdasco → replaced by Thiago Seyboth Wild
Retirements
Doubles main draw entrants
Seeds
- 1 Rankings are as of 12 July 2021.
Other entrants
The following pairs received wildcards into the doubles main draw:Withdrawals
;Before the tournament- Kamil Majchrzak / Szymon Walków → replaced by Szymon Walków / Jan Zieliński
- Elias Ymer / Mikael Ymer → replaced by Dustin Brown / Tristan-Samuel Weissborn
- Yannick Hanfmann / Marc Polmans → replaced by Zizou Bergs / Tallon Griekspoor