# 2021 IBG Prague Open – Singles

Aslan Karatsev was the defending champion but chose not to defend his title.
Franco Agamenone won the title after defeating Ryan Peniston 6–3, 6–1 in the final.

## Seeds

* Evgeny Karlovskiy (quarterfinals)
* Alexander Ritschard (second round)
* Evgenii Tiurnev (first round)
* Geoffrey Blancaneaux (second round)
* Jonáš Forejtek (first round)
* Michael Geerts (quarterfinals)
* Filip Jianu (first round)
* Miljan Zekić (first round, retired)

## 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 | Final | Final | Final |
| Genaro Alberto Olivieri | 1 | 5 | | | |
| Ryan Peniston | 6 | 7 | | | |
| Ryan Peniston | 6 | 7 | Ryan Peniston | 3 | 1 |
| | | | Franco Agamenone | 6 | 6 |
| Franco Agamenone | 6 | 6 | Franco Agamenone | 6 | 6 |
| Igor Sijsling | 3 | 0 | | | |

### 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 | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals |
| 1 | E Karlovskiy | 6 | 6 | | | | | | | | | | | | | | |
| | H Casanova | 2 | 3 | | 1 | E Karlovskiy | 5 | 6 | 6 | | | | | | | | |
| | R Molleker | 7 | 4 | 6 | | R Molleker | 7 | 4 | 2 | | | | | | | | |
| WC | A Paulson | 5 | 6 | 1 | | | | | | 1 | E Karlovskiy | 7$^8$ | 4 | 4 | | | |
| | Y-h Hsu | 6 | 6 | | | | | | | | GA Olivieri | 6$^6$ | 6 | 6 | | | |
| | A Vatutin | 3 | 0 | | | Y-h Hsu | 3 | 4 | | | | | | | | | |
| | GA Olivieri | 6 | 6 | | | GA Olivieri | 6 | 6 | | | | | | | | | |
| 5 | J Forejtek | 2 | 4 | | | | | | | | | | | | GA Olivieri | 1 | 5 |
| 3 | E Tiurnev | 6$^6$ | 2 | | | | | | | | | | | | R Peniston | 6 | 7 |
| | M Pecotić | 7$^8$ | 6 | | | M Pecotić | 3 | 6$^7$ | | | | | | | | | |
| Q | F Díaz Acosta | 6 | 6 | | Q | F Díaz Acosta | 6 | 7$^9$ | | | | | | | | | |
| PR | M Donati | 1 | 3 | | | | | | | Q | F Díaz Acosta | 3 | 1 | | | | |
| Q | Z Piros | 4 | 3 | | | | | | | | R Peniston | 6 | 6 | | | | |
| Q | U Ignatik | 6 | 6 | | Q | U Ignatik | 2 | 6 | 3 | | | | | | | | |
| | R Peniston | 6 | 4 | | | R Peniston | 6 | 2 | 6 | | | | | | | | |
| 8 | M Zekić | 0 | 1$^r$ | | | | | | | | | | | | | | |

### 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 |
| 6 | M Geerts | 6 | 6 | | | | | | | | | | | | | | |
| WC | Martin Krumich | 2 | 4 | | 6 | M Geerts | 6 | 6 | | | | | | | | | |
| | J Härteis | 4 | 2 | | Q | A Rybakov | 2 | 2 | | | | | | | | | |
| Q | A Rybakov | 6 | 6 | | | | | | | 6 | M Geerts | 7 | 5 | 3 | | | |
| | N Sánchez Izquierdo | 3 | 3 | | | | | | | | F Agamenone | 5 | 7 | 6 | | | |
| | F Agamenone | 6 | 6 | | | F Agamenone | 7 | 6 | | | | | | | | | |
| | A Cazaux | 4 | 6$^6$ | | 4 | G Blancaneaux | 5 | 4 | | | | | | | | | |
| 4 | G Blancaneaux | 6 | 7$^8$ | | | | | | | | | | | | F Agamenone | 6 | 6 |
| 7 | FC Jianu | 6$^4$ | 2 | | | | | | | | | | | | I Sijsling | 3 | 0 |
| | M Pucinelli de Almeida | 7$^7$ | 6 | | | M Pucinelli de Almeida | 2 | 6 | 2$^r$ | | | | | | | | |
| WC | Daniel Siniakov | 4 | 3 | | | I Sijsling | 6 | 2 | 3 | | | | | | | | |
| | I Sijsling | 6 | 6 | | | | | | | | I Sijsling | 7 | 6 | | | | |
| | K Uchida | 6 | 3 | 6 | | | | | | | K Uchida | 5 | 3 | | | | |
| | N Chappell | 4 | 6 | 1 | | K Uchida | 7$^7$ | 7 | | | | | | | | | |
| | R Ortega Olmedo | 1 | 1 | | 2 | A Ritschard | 6$^4$ | 5 | | | | | | | | | |
| 2 | A Ritschard | 6 | 6 | | | | | | | | | | | | | | |