# 2023 Heilbronner Neckarcup – Singles

Daniel Altmaier was the defending champion but chose not to defend his title.
Matteo Arnaldi won the title after defeating Facundo Díaz Acosta 7–6$^{(7–4)}$, 6–1 in the final.

## Seeds

* Marco Cecchinato (first round)
* Jaume Munar (quarterfinals)
* Daniel Elahi Galán (quarterfinals)
* Dominic Thiem (second round)
* Matteo Arnaldi (champion)
* Fábián Marozsán (second round)
* Oscar Otte (first round)
* Pavel Kotov (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 |
| | Facundo Díaz Acosta | 7 | 6 | | | | |
| WC | Rudolf Molleker | 5 | 3 | | | | |
| WC | Rudolf Molleker | 5 | 3 | | Facundo Díaz Acosta | 6$^4$ | 1 |
| | | | | 5 | Matteo Arnaldi | 7$^7$ | 6 |
| | Pedro Martínez | 6$^4$ | 5 | 5 | Matteo Arnaldi | 7$^7$ | 6 |
| 5 | Matteo Arnaldi | 7$^7$ | 7 | | | | |

### 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 | M Cecchinato | 5 | 3 | | | | | | | | | | | | | | | |
| Q | A Santillan | 7 | 6 | | Q | A Santillan | 6 | 3 | 6 | | | | | | | | | |
| | J Kovalík | 3 | 6 | 7$^7$ | | J Kovalík | 2 | 6 | 3 | | | | | | | | | |
| | M Marterer | 6 | 2 | 6$^5$ | | | | | | Q | A Santillan | 5 | 3 | | | | | |
| LL | M Janvier | 6 | 6 | | | | | | | | F Díaz Acosta | 7 | 6 | | | | | |
| Q | Lucas Gerch | 4 | 3 | | LL | M Janvier | 1 | 6 | 6$^5$ | | | | | | | | | |
| | F Díaz Acosta | 6 | 6$^1$ | 6 | | F Díaz Acosta | 6 | 3 | 7$^7$ | | | | | | | | | |
| 7 | O Otte | 4 | 7$^7$ | 1 | | | | | | | | | | | | F Díaz Acosta | 7 | 6 |
| 3 | DE Galán | 6 | 7$^7$ | | | | | | | | | | | | WC | R Molleker | 5 | 3 |
| Alt | C İlkel | 4 | 6$^3$ | | 3 | DE Galán | 5 | 6 | 6 | | | | | | | | | |
| Q | J Kym | 6$^2$ | 3 | | | F Meligeni Alves | 7 | 0 | 2 | | | | | | | | | |
| | F Meligeni Alves | 7$^7$ | 6 | | | | | | | 3 | DE Galán | 4 | 7 | 5 | | | | |
| Q | S Fanselow | 4 | 7$^7$ | 1 | | | | | | WC | R Molleker | 6 | 5 | 7 | | | | |
| WC | R Molleker | 6 | 6$^5$ | 6 | WC | R Molleker | 7 | 6 | | | | | | | | | | |
| Alt | H Casanova | 3 | 4 | | 6 | F Marozsán | 5 | 4 | | | | | | | | | | |
| 6 | F Marozsán | 6 | 6 | | | | | | | | | | | | | | | |

### Bottom half

| 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 |
| 8 | P Kotov | 7$^8$ | 6 | | | | | | | | | | | | | | |
| | A Pellegrino | 6$^6$ | 2 | 8 | P Kotov | 6 | 6 | | | | | | | | | | |
| Q | MH Rehberg | 2 | 4$^r$ | Alt | D Added | 2 | 2 | | | | | | | | | | |
| Alt | D Added | 6 | 5 | | | | | | 8 | P Kotov | 4 | 6 | 6$^3$ | | | | |
| Q | H Squire | 4 | 2 | | | | | | | P Martínez | 6 | 4 | 7$^7$ | | | | |
| | P Martínez | 6 | 6 | | P Martínez | 2 | 6 | 6 | | | | | | | | | |
| | K Uchida | 4 | 4 | 4/WC | D Thiem | 6 | 3 | 1 | | | | | | | | | |
| 4/WC | D Thiem | 6 | 6 | | | | | | | | | | | | P Martínez | 6$^4$ | 5 |
| 5 | M Arnaldi | 7 | 6 | | | | | | | | | | | 5 | M Arnaldi | 7$^7$ | 7 |
| | N Gombos | 5 | 3 | 5 | M Arnaldi | 2 | 6 | 6 | | | | | | | | | |
| | O Krutykh | 4 | 4 | WC | M Topo | 6 | 3 | 1 | | | | | | | | | |
| WC | M Topo | 6 | 6 | | | | | | 5 | M Arnaldi | 1 | 6 | 7 | | | | |
| | D Džumhur | 5 | 1 | | | | | | 2 | J Munar | 6 | 4 | 5 | | | | |
| | T Skatov | 7 | 6 | | T Skatov | 2 | 5 | | | | | | | | | | |
| | H Dellien | 1 | 1 | 2 | J Munar | 6 | 7 | | | | | | | | | | |
| 2 | J Munar | 6 | 6 | | | | | | | | | | | | | | |