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.

[1] *per team The following players received wildcards into the singles main draw: The following players received entry from the qualifying draw: The following player received entry as a lucky loser: The following pairs received wildcards into the doubles main draw: