| 2021 Banja Luka Challenger | |
|---|---|
| Date | 6–12 September |
| Edition | 19th |
| Surface | Clay |
| Location | Banja Luka, Bosnia and Herzegovina |
| Champions | |
| Singles | |
 Juan Manuel Cerúndolo | |
| Doubles | |
 Antonio Šančić / Nino Serdarušić | |
The 2021 Banja Luka Challenger was a professional tennis tournament played on clay courts. It was the nineteenth edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Banja Luka, Bosnia and Herzegovina from 6 to 12 September 2021.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 SVK | Andrej Martin | 122 | 1 |
| ARG | Juan Manuel Cerúndolo | 135 | 2 |
| ARG | Tomás Martín Etcheverry | 142 | 3 |
 SRB | Nikola Milojević | 160 | 4 |
 IND | Sumit Nagal | 164 | 5 |
| SRB | Danilo Petrović | 177 | 6 |
 CZE | Zdeněk Kolář | 182 | 7 |
| CZE | Vít Kopřiva | 202 | 8 |
The following players received wildcards into the singles main draw:
Dražen Petrović Vladan Tadić Marko Topo The following players received entry from the qualifying draw:
Martín Cuevas 
Jonathan Mridha David Poljak Marko Tepavac Juan Manuel Cerúndolo def. Nikola Milojević 6–3, 6–1. Antonio Šančić / Nino Serdarušić def. Ivan Sabanov / Matej Sabanov 6–3, 6–3.