The 2021 Split Open was a professional tennis tournament played on clay courts. It was part of the 2021 ATP Challenger Tour. It took place in Split, Croatia between 5 and 11 April 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Pedro Sousa | 111 | 1 | ||
 Australia | Marc Polmans | 137 | 2 | |
 Austria | Sebastian Ofner | 152 | 3 | |
 Egypt | Mohamed Safwat | 159 | 4 | |
 Serbia | Danilo Petrović | 160 | 5 | |
| Blaž Rola | 166 | 6 | ||
 Belgium | Kimmer Coppejans | 170 | 7 | |
 Slovakia | Filip Horanský | 175 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry into the singles main draw using protected rankings:
The following player received entry into the singles main draw as a special exempt:
The following player received entry into the singles main draw as an alternate:
The following players received entry from the qualifying draw:
See main article: 2021 Split Open – Singles.
See main article: 2021 Split Open – Doubles.
Andrey Golubev / Aleksandr Nedovyesov def. 
Szymon Walków / Jan Zieliński 7–5, 6–7(5–7), [10–5].
