# 2023 Open de Oeiras II – Singles

Zsombor Piros was the defending champion but chose not to defend his title.
Facundo Díaz Acosta won the title after defeating Aleksandar Vukic 6–4, 6–3 in the final.

## Seeds

* Pedro Cachin (quarterfinals)
* Hugo Gaston (first round, retired)
* Radu Albot (quarterfinals)
* Emilio Gómez (first round)
* Facundo Bagnis (first round)
* Aleksandar Vukic (final)
* Facundo Díaz Acosta (champion)
* Rinky Hijikata (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 |
| | Nicolas Moreno de Alboran | 6$^9$ | 2 | | | | | |
| 7 | Facundo Díaz Acosta | 7$^{11}$ | 6 | | | | | |
| 7 | Facundo Díaz Acosta | 7$^{11}$ | 6 | | 7 | Facundo Díaz Acosta | 6 | 6 |
| | | | | | 6 | Aleksandar Vukic | 4 | 3 |
| 6 | Aleksandar Vukic | 5 | 6 | 6 | 6 | Aleksandar Vukic | 4 | 3 |
| | Felipe Meligeni Alves | 7 | 4 | 4 | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | P Cachin | 5 | 7$^7$ | 6 | | | | | | | | | | | | |
| Q | E Ribeiro | 7 | 6$^5$ | 3 | 1 | P Cachin | 6 | 6 | | | | | | | | |
| | H Dellien | 6 | 6 | | | H Dellien | 4 | 2 | | | | | | | | |
| | I Gakhov | 1 | 3 | | | | | | 1 | P Cachin | 1 | 4 | | | | |
| | N Moreno de Alboran | 6 | 2 | 6 | | | | | | N Moreno de Alboran | 6 | 6 | | | | |
| Alt | F Delbonis | 2 | 6 | 1 | | N Moreno de Alboran | 6 | 6 | | | | | | | | |
| | S Johnson | 1 | 7$^7$ | 6 | | S Johnson | 3 | 0 | | | | | | | | |
| 8 | R Hijikata | 6 | 6$^3$ | 1 | | | | | | | | | | N Moreno de Alboran | 6$^9$ | 2 |
| 3 | R Albot | 6 | 6 | | | | | | | | | | 7 | F Díaz Acosta | 7$^{11}$ | 6 |
| Alt | A Andreev | 1 | 3 | | 3 | R Albot | 7$^7$ | 6 | | | | | | | | |
| | J Choinski | 6 | 4 | 6 | | J Choinski | 6$^3$ | 4 | | | | | | | | |
| Q | A Giannessi | 3 | 6 | 4 | | | | | 3 | R Albot | 2 | 2 | | | | |
| Q | U Blanch | 6 | 7$^7$ | | | | | | 7 | F Díaz Acosta | 6 | 6 | | | | |
| WC | P Sousa | 2 | 6$^4$ | | Q | U Blanch | 4 | 5 | | | | | | | | |
| | Em Nava | 1 | 6$^3$ | | 7 | F Díaz Acosta | 6 | 7 | | | | | | | | |
| 7 | F Díaz Acosta | 6 | 7$^7$ | | | | | | | | | | | | | |

### 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 | Semifinals |
| 6 | A Vukic | 7$^7$ | 6 | | | | | | | | | | | | | | | |
| WC | F Ferreira Silva | 6$^3$ | 3 | | 6 | A Vukic | 6 | 4 | 6 | | | | | | | | | |
| | Gerard Campana Lee | 6 | 6 | | | G Campana Lee | 4 | 6 | 3 | | | | | | | | | |
| Q | M Guinard | 3 | 2 | | | | | | | 6 | A Vukic | 7 | 6 | | | | | |
| | M Landaluce | 5 | 1 | | | | | | | | A Ritschard | 5 | 3 | | | | | |
| | A Ritschard | 7 | 6 | | | A Ritschard | 6 | 6 | | | | | | | | | | |
| Q | M Valkusz | 6 | 6 | | Q | M Valkusz | 3 | 0 | | | | | | | | | | |
| 4 | E Gómez | 0 | 1 | | | | | | | | | | | 6 | A Vukic | 5 | 6 | 6 |
| 5 | F Bagnis | 4 | 4 | | | | | | | | | | | | F Meligeni Alves | 7 | 4 | 4 |
| | O Krutykh | 6 | 6 | | | O Krutykh | 6$^2$ | 6$^4$ | | | | | | | | | | |
| | F Meligeni Alves | 6 | 6 | | | F Meligeni Alves | 7$^7$ | 7$^7$ | | | | | | | | | | |
| | R Brancaccio | 1 | 2 | | | | | | | | F Meligeni Alves | 7 | 6 | | | | | |
| WC | J Domingues | 6 | 0 | 2 | | | | | | | P Martínez | 5 | 3 | | | | | |
| Q | N Serdarušić | 4 | 6 | 6 | Q | N Serdarušić | 3 | 6$^5$ | | | | | | | | | | |
| | P Martínez | 6 | 3 | | | P Martínez | 6 | 7$^7$ | | | | | | | | | | |
| 2 | H Gaston | 3 | 0$^r$ | | | | | | | | | | | | | | | |