# 2021 Bratislava Open – Singles

Norbert Gombos was the defending champion but lost in the second round to Filip Horanský.
Tallon Griekspoor won the title after defeating Sebastián Báez 7–6$^{(8–6)}$, 6–3 in the final.

## Seeds

* Norbert Gombos (second round)
* Federico Coria (second round)
* Hugo Dellien (first round)
* Jozef Kovalík (second round)
* Tallon Griekspoor (champion)
* Juan Manuel Cerúndolo (second round)
* Blaž Rola (first round)
* Frederico Ferreira Silva (second round)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| | Filip Horanský | 7$^8$ | 4 | 6$^7$ | | | | |
| | Sebastián Báez | 6$^6$ | 6 | 7$^9$ | | | | |
| | Sebastián Báez | 6$^6$ | 6 | 7$^9$ | | Sebastián Báez | 6$^6$ | 3 |
| | | | | | 5 | Tallon Griekspoor | 7$^8$ | 6 |
| | Martin Kližan | 4 | 7 | 4 | 5 | Tallon Griekspoor | 7$^8$ | 6 |
| 5 | Tallon Griekspoor | 6 | 5 | 6 | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | N Gombos | 6 | 6 | | | | | | | | | | | | | |
| | Y Maden | 3 | 3 | | 1 | N Gombos | 2 | 2 | | | | | | | | |
| | M Marterer | 2 | 4 | | | F Horanský | 6 | 6 | | | | | | | | |
| | F Horanský | 6 | 6 | | | | | | | F Horanský | 6 | 6 | | | | |
| | E Benchetrit | 5 | 2 | | | | | | | C İlkel | 3 | 4 | | | | |
| | C İlkel | 7 | 6 | | | C İlkel | 6 | 6 | | | | | | | | |
| | F Mena | 6 | 6 | | | F Mena | 3 | 4 | | | | | | | | |
| 7 | B Rola | 4 | 2 | | | | | | | | | | F Horanský | 7$^8$ | 4 | 6$^7$ |
| 4 | J Kovalík | 6 | 6 | | | | | | | | | | S Báez | 6$^6$ | 6 | 7$^9$ |
| Q | V Kopřiva | 4 | 2 | | 4 | J Kovalík | 7$^7$ | 1 | 4 | | | | | | | |
| | Q Halys | 6$^3$ | 2 | | | M Bachinger | 6$^1$ | 6 | 6 | | | | | | | |
| | M Bachinger | 7$^7$ | 6 | | | | | | | M Bachinger | 6$^6$ | 6$^0$ | | | | |
| | S Báez | 1 | 6 | 6 | | | | | | S Báez | 7$^8$ | 7$^7$ | | | | |
| | R Olivo | 6 | 1 | 3 | | S Báez | 6 | 5 | 6 | | | | | | | |
| | T Kamke | 4 | 4 | | 8 | F Ferreira Silva | 3 | 7 | 4 | | | | | | | |
| 8 | F Ferreira Silva | 6 | 6 | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 6 | JM Cerúndolo | 6 | 6 | | | | | | | | | | | | | | | | |
| WC | M Karol | 4 | 2 | | 6 | JM Cerúndolo | 7$^7$ | 3 | 5 | | | | | | | | | | |
| | M Moraing | 6$^2$ | 7$^7$ | 5 | | M Kližan | 6$^0$ | 6 | 7 | | | | | | | | | | |
| | M Kližan | 7$^7$ | 6$^3$ | 7 | | | | | | | M Kližan | 7$^7$ | 6 | | | | | | |
| WC | A Molčan | 7$^8$ | 6 | | | | | | | PR | A Kuznetsov | 6$^4$ | 2 | | | | | | |
| Q | D Ajduković | 6$^6$ | 4 | | WC | A Molčan | 4 | 4 | | | | | | | | | | | |
| PR | A Kuznetsov | 6 | 4 | 6 | PR | A Kuznetsov | 6 | 6 | | | | | | | | | | | |
| 3 | H Dellien | 2 | 6 | 3 | | | | | | | | | | | | M Kližan | 4 | 7 | 4 |
| 5 | T Griekspoor | 7$^7$ | 7$^7$ | | | | | | | | | | | | 5 | T Griekspoor | 6 | 5 | 6 |
| Q | U Ignatik | 6$^1$ | 6$^2$ | | 5 | T Griekspoor | 6 | 3 | 6 | | | | | | | | | | |
| LL | L Miedler | 2 | 4 | | | S Diez | 4 | 6 | 4 | | | | | | | | | | |
| | S Diez | 6 | 6 | | | | | | | 5 | T Griekspoor | 2 | 6 | 6 | | | | | |
| WC | L Klein | 6 | 3 | 6$^4$ | | | | | | Q | J Lehečka | 6 | 3 | 2 | | | | | |
| Q | J Lehečka | 4 | 6 | 7$^7$ | Q | J Lehečka | 7$^7$ | 7$^8$ | | | | | | | | | | | |
| | Z Kolář | 7$^8$ | 0 | 5 | 2 | F Coria | 6$^5$ | 6$^6$ | | | | | | | | | | | |
| 2 | F Coria | 6$^6$ | 6 | 7 | | | | | | | | | | | | | | | |