# 2023 Oeiras Indoors II – Singles

Joris De Loore was the defending champion but lost in the final to Arthur Fils.
Fils won the title after defeating De Loore 6–1, 7–6$^{(7–4)}$ in the final.

## Seeds

* Ričardas Berankis (semifinals)
* Jay Clarke (second round)
* Matteo Gigante (first round)
* Arthur Fils (champion)
* Hamad Međedović (first round)
* Harold Mayot (first round)
* Nikolás Sánchez Izquierdo (first round)
* Steven Diez (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 | Final | Final | Final | Final |
| 1 | Ričardas Berankis | 5 | 3 | | | | |
| 4 | Arthur Fils | 7 | 6 | | | | |
| 4 | Arthur Fils | 7 | 6 | 4 | Arthur Fils | 6 | 7$^7$ |
| | | | | SE | Joris De Loore | 1 | 6$^4$ |
| | Pierre-Hugues Herbert | 2 | 4 | SE | Joris De Loore | 1 | 6$^4$ |
| SE | Joris De Loore | 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 | R Berankis | 7$^7$ | 6 | | | | | | | | | | | | | | |
| | M Valkusz | 6$^3$ | 1 | | 1 | R Berankis | 5 | 6 | 6 | | | | | | | | |
| Q | M Lajal | 4 | 4$^r$ | | | L Gerch | 7 | 4 | 4 | | | | | | | | |
| | Lucas Gerch | 6 | 5 | | | | | | | 1 | R Berankis | 7 | 7$^8$ | | | | |
| | E Karlovskiy | 0 | 0$^r$ | | | | | | | Q | D Prižmić | 5 | 6$^6$ | | | | |
| Q | D Prižmić | 6 | 3 | | Q | D Prižmić | 2 | 6 | 6 | | | | | | | | |
| Q | S Fanselow | 6 | 3 | 6 | Q | S Fanselow | 6 | 2 | 2 | | | | | | | | |
| 6 | H Mayot | 2 | 6 | 4 | | | | | | | | | | 1 | R Berankis | 5 | 3 |
| 4 | A Fils | 6 | 0 | 6 | | | | | | | | | | 4 | A Fils | 7 | 6 |
| | L Wessels | 3 | 6 | 2 | 4 | A Fils | 7 | 6 | | | | | | | | | |
| | J Domingues | 2 | 3 | | Q | C İlkel | 5 | 2 | | | | | | | | | |
| Q | C İlkel | 6 | 6 | | | | | | | 4 | A Fils | 6 | 6 | | | | |
| | L Neumayer | 2 | 2 | | | | | | | | M Neuchrist | 3 | 1 | | | | |
| WC | G Oliveira | 6 | 6 | | WC | G Oliveira | 6$^4$ | 3 | | | | | | | | | |
| | M Neuchrist | 4 | 6 | 7 | | M Neuchrist | 7$^7$ | 6 | | | | | | | | | |
| 8 | S Diez | 6 | 3 | 5 | | | | | | | | | | | | | |

### 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 |
| 7 | N Sánchez Izquierdo | 6$^3$ | 3 | | | | | | | | | | | | | | |
| WC | P Sousa | 7$^7$ | 6 | | WC | P Sousa | 3 | 7 | 6 | | | | | | | | |
| Q | G Décamps | 6$^1$ | 7$^7$ | 4 | | P Martín Tiffon | 6 | 5 | 4 | | | | | | | | |
| | Pol Martín Tiffon | 7$^7$ | 6$^5$ | 6 | | | | | | WC | P Sousa | 1 | 4 | | | | |
| | A Dougaz | 4 | 5 | | | | | | | | P-H Herbert | 6 | 6 | | | | |
| | FC Jianu | 6 | 7 | | | FC Jianu | 6 | 3 | 2 | | | | | | | | |
| | P-H Herbert | 3 | 6 | 6 | | P-H Herbert | 3 | 6 | 6 | | | | | | | | |
| 3 | M Gigante | 6 | 4 | 4 | | | | | | | | | | | P-H Herbert | 2 | 4 |
| 5 | H Međedović | 6$^4$ | 3 | | | | | | | | | | | SE | J De Loore | 6 | 6 |
| SE | J De Loore | 7$^7$ | 6 | | SE | J De Loore | 6 | 6 | | | | | | | | | |
| | V Vacherot | 5 | 4 | | | R Collignon | 4 | 3 | | | | | | | | | |
| | R Collignon | 7 | 6 | | | | | | | SE | J De Loore | 6 | 6 | | | | |
| Q | Elmar Ejupovic | 4 | 5 | | | | | | | | L Giustino | 2 | 4 | | | | |
| | L Giustino | 6 | 7 | | | L Giustino | 6 | 7$^7$ | | | | | | | | | |
| WC | J Faria | 4 | 3 | | 2 | J Clarke | 3 | 6$^4$ | | | | | | | | | |
| 2 | J Clarke | 6 | 6 | | | | | | | | | | | | | | |