| 2021 Zagreb Open | |
|---|---|
| Date | 10–16 May 2021 |
| Edition | 17th |
| Surface | Clay |
| Location | Zagreb, Croatia |
| Champions | |
| Singles | |
 Sebastián Báez | |
| Doubles | |
 Evan King / Hunter Reese | |
The 2021 Zagreb Open was a professional tennis tournament played on clay courts. It was part of the 2021 ATP Challenger Tour. It took place in Zagreb, Croatia between 10 and 16 May 2021.