| Date: | 7–13 June |
| Edition: | 2nd |
| Category: | ATP Challenger Tour |
| Surface: | Clay |
| Location: | Bratislava, Slovakia |
| Champs: | Tallon Griekspoor |
| Champd: |  Denys Molchanov /  Aleksandr Nedovyesov |
| Before Year: | 2019 |
The 2021 Bratislava Open was a professional tennis tournament played on clay courts. It was the 2nd edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Bratislava, Slovakia between 7 and 13 June 2021.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Slovakia | Norbert Gombos | 81 | 1 | |
 Argentina | Federico Coria | 94 | 2 | |
 Bolivia, Plurination;al State of | Hugo Dellien | 124 | 3 | |
| Slovakia | Jozef Kovalík | 127 | 4 | |
| Tallon Griekspoor | 131 | 5 | ||
| Argentina | Juan Manuel Cerúndolo | 147 | 6 | |
| Blaž Rola | 155 | 7 | ||
| Frederico Ferreira Silva | 168 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw using a protected ranking:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
See main article: 2021 Bratislava Open – Singles.
Sebastián Báez 7–6(8–6), 6–3.See main article: 2021 Bratislava Open – Doubles.
Denys Molchanov / Aleksandr Nedovyesov def. Sander Arends / 
Luis David Martínez 7–6(7–5), 6–1.
