# 2023 Koblenz Open – Singles

Tomáš Macháč was the defending champion but chose not to defend his title.
Roman Safiullin won the title after defeating Vasek Pospisil 6–2, 7–5 in the final.

## Seeds

* Zhang Zhizhen (second round)
* Roman Safiullin (champion)
* Vasek Pospisil (final)
* Maximilian Marterer (quarterfinals, retired)
* Hugo Grenier (second round)
* Liam Broady (second round)
* Alexandre Müller (quarterfinals)
* Gijs Brouwer (first 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 |
| | Zdeněk Kolář | 1 | 3 | | | | | |
| 3 | Vasek Pospisil | 6 | 6 | | | | | |
| 3 | Vasek Pospisil | 6 | 6 | | 3 | Vasek Pospisil | 2 | 5 |
| | | | | | 2 | Roman Safiullin | 6 | 7 |
| Alt | Raphaël Collignon | 7 | 3 | 0 | 2 | Roman Safiullin | 6 | 7 |
| 2 | Roman Safiullin | 5 | 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | Zh Zhang | 6 | 5 | 6 | | | | | | | | | | | | | | |
| WC | H Squire | 1 | 7 | 4 | 1 | Zh Zhang | 6 | 3 | 3 | | | | | | | | | |
| | Z Kolář | 6 | 6 | | | Z Kolář | 3 | 6 | 6 | | | | | | | | | |
| | A Bellier | 2 | 4 | | | | | | | | Z Kolář | 7$^7$ | 4 | 7$^7$ | | | | |
| | J Choinski | 6 | 1 | 6 | | | | | | 7 | A Müller | 6$^5$ | 6 | 6$^3$ | | | | |
| Q | D Yevseyev | 4 | 6 | 2 | | J Choinski | 3 | 7$^7$ | 5 | | | | | | | | | |
| WC | MH Rehberg | 4 | 4 | | 7 | A Müller | 6 | 6$^4$ | 7 | | | | | | | | | |
| 7 | A Müller | 6 | 6 | | | | | | | | | | | | | Z Kolář | 1 | 3 |
| 3 | V Pospisil | 7 | 6 | | | | | | | | | | | | 3 | V Pospisil | 6 | 6 |
| | Em Nava | 5 | 2 | | 3 | V Pospisil | 7$^8$ | 7$^7$ | | | | | | | | | | |
| Q | M Rosenkranz | 4 | 6 | 6 | Q | M Rosenkranz | 6$^6$ | 6$^2$ | | | | | | | | | | |
| | L Lokoli | 6 | 4 | 3 | | | | | | 3 | V Pospisil | 6 | 6 | | | | | |
| Q | A Hoang | 6$^6$ | 6 | 2 | | | | | | Alt | L Wessels | 4 | 2 | | | | | |
| Alt | L Wessels | 7$^8$ | 3 | 6 | Alt | L Wessels | 6 | 6 | | | | | | | | | | |
| Alt | Lucas Gerch | 2 | 2 | | 5 | H Grenier | 4 | 3 | | | | | | | | | | |
| 5 | H Grenier | 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 |
| 8 | G Brouwer | 7 | 6$^2$ | 3 | | | | | | | | | | | | | | | |
| Alt | R Collignon | 5 | 7$^7$ | 6 | Alt | R Collignon | 7 | 6 | | | | | | | | | | | |
| | L Nardi | 6$^9$ | 3 | | | H Laaksonen | 5 | 4 | | | | | | | | | | | |
| | H Laaksonen | 7$^{11}$ | 6 | | | | | | | Alt | R Collignon | 5 | | | | | | | |
| Alt | D Masur | 5 | 3 | | | | | | | 4 | M Marterer | 2$^r$ | | | | | | | |
| | A Andreev | 7 | 6 | | | A Andreev | 3 | 3 | | | | | | | | | | | |
| Q | V Sachko | 5 | 2 | | 4 | M Marterer | 6 | 6 | | | | | | | | | | | |
| 4 | M Marterer | 7 | 6 | | | | | | | | | | | | Alt | R Collignon | 7 | 3 | 0 |
| 6 | L Broady | 7$^7$ | 6 | | | | | | | | | | | | 2 | R Safiullin | 5 | 6 | 6 |
| Alt | R Haase | 6$^2$ | 1 | | 6 | L Broady | 2 | 3 | | | | | | | | | | | |
| Q | A Vatutin | 7$^8$ | 6 | | Q | A Vatutin | 6 | 6 | | | | | | | | | | | |
| Q | J Härteis | 6$^6$ | 1 | | | | | | | Q | A Vatutin | 3 | 6 | 2 | | | | | |
| WC | M Topo | 4 | 7$^7$ | 6$^6$ | | | | | | 2 | R Safiullin | 6 | 1 | 6 | | | | | |
| | A Escoffier | 6 | 6$^5$ | 7$^8$ | | A Escoffier | 3 | 6 | 6$^2$ | | | | | | | | | | |
| | G Blancaneaux | 7 | 3 | 1 | 2 | R Safiullin | 6 | 4 | 7$^7$ | | | | | | | | | | |
| 2 | R Safiullin | 5 | 6 | 6 | | | | | | | | | | | | | | | |