Carlos Alcaraz defeated Richard Gasquet in the final, 6–2, 6–2 to win the singles tennis title at the 2021 Croatia Open Umag. It was his first ATP Tour title. Alcaraz was the youngest player to win an ATP Tour title since Kei Nishikori at the 2008 Delray Beach International Tennis Championships.
Dušan Lajović was the reigning champion from when the tournament was last held in 2019, but lost to Daniel Altmaier in the quarterfinals.
Seeds The top four seeds receive a bye into the second round.
Draw
Finals
Top half
Bottom half
Qualifying
Seeds
Qualifiers
Lucky loser
Qualifying draw
First qualifier
Second qualifier
Third qualifier
Fourth qualifier
References
External links Main draw Qualifying draw