| Champ: |  Pablo Carreño Busta |
| Runner: |  Filip Krajinović |
| Score: | 6–2, 6–4 |
| Draw: | 28 (6 / 4) |
| Seeds: | 8 |
| Main Name: | Hamburg European Open |
| Before Name: | Hamburg European Open – Singles |
See main article: article and 2021 Hamburg European Open.
Andrey Rublev was the defending champion,[1] but chose to not defend his title as he and other Russian Olympic athletes were sent to Yuzhno-Sakhalinsk for training sessions.[2]
Pablo Carreño Busta won his maiden ATP Tour 500 singles title, defeating Filip Krajinović in the final, 6–2, 6–4.
The top four seeds received a bye into the second round.