# 2021 I.ČLTK Prague Open – Men's singles

The men's singles of the 2021 I.ČLTK Prague Open tournament was played on clay in Prague, Czech Republic.
Stan Wawrinka was the defending champion but chose not to partake in this edition.
Tallon Griekspoor won the title after defeating Oscar Otte 5–7, 6–4, 6–4 in the final.

## Seeds

* Norbert Gombos (semifinals)
* Yūichi Sugita (first round, retired)
* Andrej Martin (second round)
* Dennis Novak (first round)
* Denis Kudla (first round)
* Kamil Majchrzak (first round)
* Peter Gojowczyk (first round)
* Sumit Nagal (quarterfinals)

## 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 | Final | Final | Final | Final |
| 1 | Norbert Gombos | 6$^5$ | 3 | | | | |
| | Tallon Griekspoor | 7$^7$ | 6 | | | | |
| | Tallon Griekspoor | 7$^7$ | 6 | Tallon Griekspoor | 5 | 6 | 6 |
| | | | | Oscar Otte | 7 | 4 | 4 |
| WC | Michael Vrbenský | 3 | 3 | Oscar Otte | 7 | 4 | 4 |
| | Oscar Otte | 6 | 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | N Gombos | 6$^6$ | 6 | 6 | | | | | | | | | | | | | |
| | H Laaksonen | 7$^8$ | 4 | 3 | 1 | N Gombos | 6 | 6$^1$ | 6 | | | | | | | | |
| Q | K Żuk | 7$^7$ | 2 | 7 | Q | K Żuk | 3 | 7$^7$ | 3 | | | | | | | | |
| | M Vilella Martínez | 6$^5$ | 6 | 5 | | | | | | 1 | N Gombos | 6 | 6 | | | | |
| | D Popko | 3 | 4 | | | | | | | 8 | S Nagal | 4 | 2 | | | | |
| Q | S Stakhovsky | 6 | 6 | | Q | S Stakhovsky | 6 | 1 | 4 | | | | | | | | |
| Q | Z Kolář | 2 | 4 | | 8 | S Nagal | 4 | 6 | 6 | | | | | | | | |
| 8 | S Nagal | 6 | 6 | | | | | | | | | | | 1 | N Gombos | 6$^5$ | 3 |
| 4 | D Novak | 4 | 6$^1$ | | | | | | | | | | | | T Griekspoor | 7$^7$ | 6 |
| SE | R Olivo | 6 | 7$^7$ | | SE | R Olivo | 3 | 6$^3$ | | | | | | | | | |
| | L Rosol | 3 | 0 | | | T Griekspoor | 6 | 7$^7$ | | | | | | | | | |
| | T Griekspoor | 6 | 6 | | | | | | | | T Griekspoor | 6 | 6 | | | | |
| | R Marcora | 6$^4$ | 2 | | | | | | | | F Ferreira Silva | 2 | 4 | | | | |
| | M Polmans | 7$^7$ | 6 | | | M Polmans | 2 | 6 | 4 | | | | | | | | |
| | F Ferreira Silva | 6 | 6$^5$ | 6 | | F Ferreira Silva | 6 | 3 | 6 | | | | | | | | |
| 6 | K Majchrzak | 4 | 7$^7$ | 1 | | | | | | | | | | | | | |

### 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 | Semifinals | Semifinals | Semifinals | Semifinals |
| 5 | D Kudla | 1 | 4 | | | | | | | | | | | | | | |
| | Y Maden | 6 | 6 | | | Y Maden | 6 | 4 | 1 | | | | | | | | |
| Q | V Kopřiva | 6 | 6$^4$ | 7$^8$ | Q | V Kopřiva | 4 | 6 | 6 | | | | | | | | |
| | I Marchenko | 2 | 7$^7$ | 6$^6$ | | | | | | Q | V Kopřiva | 1 | 4 | | | | |
| WC | M Vrbenský | 7$^7$ | 6 | | | | | | | WC | M Vrbenský | 6 | 6 | | | | |
| | S Ofner | 6$^4$ | 3 | | WC | M Vrbenský | 6 | 1 | 6 | | | | | | | | |
| WC | A Paulson | 3 | 3 | | 3 | A Martin | 4 | 6 | 4 | | | | | | | | |
| 3 | A Martin | 6 | 6 | | | | | | | | | | | WC | M Vrbenský | 3 | 3 |
| 7 | P Gojowczyk | 3 | 1 | | | | | | | | | | | | O Otte | 6 | 6 |
| | O Otte | 6 | 6 | | | O Otte | 6 | 3 | 6 | | | | | | | | |
| WC | J Lehečka | 4 | 6 | 7$^7$ | WC | J Lehečka | 1 | 6 | 3 | | | | | | | | |
| | R Safiullin | 6 | 3 | 6$^4$ | | | | | | | O Otte | 6 | 7 | | | | |
| | M Cressy | 6 | 6 | | | | | | | | M Cressy | 3 | 5 | | | | |
| | M Safwat | 2 | 2 | | | M Cressy | 6 | 7 | | | | | | | | | |
| | A Tabilo | 7 | 4 | | | A Tabilo | 2 | 5 | | | | | | | | | |
| 2 | Y Sugita | 5 | 0$^r$ | | | | | | | | | | | | | | |