| 2021 Zadar Open | |
|---|---|
| Date | 22–28 March |
| Edition | 1st |
| Surface | Clay |
| Location | Zadar, Croatia |
| Champions | |
| Singles | |
 Nikola Milojević | |
| Doubles | |
 Blaž Kavčič / Blaž Rola | |
The 2021 Zadar Open was a professional tennis tournament played on clay courts. It was the first edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Zadar, Croatia between 22 and 28 March 2021.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 ITA | Gianluca Mager | 101 | 1 |
 IND | Sumit Nagal | 139 | 2 |
| SRB | Nikola Milojević | 146 | 3 |
| SLO | Blaž Rola | 165 | 4 |
| ITA | Alessandro Giannessi | 167 | 5 |
 SVK | Filip Horanský | 173 | 6 |
 FRA | Enzo Couacaud | 185 | 7 |
| ITA | Gian Marco Moroni | 233 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
The following players received entry as lucky losers:
Nikola Milojević def. 
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