# 2023 Lisboa Belém Open – Men's singles

Marco Cecchinato was the defending champion but chose not to defend his title.
Flavio Cobolli won the title after defeating Benjamin Hassan 7–5, 7–5 in the final.

## Seeds

* Albert Ramos Viñolas (semifinals)
* Flavio Cobolli (champion)
* Timofey Skatov (first round)
* Pablo Llamas Ruiz (second round)
* Ivan Gakhov (second round)
* Titouan Droguet (first round)
* Zdeněk Kolář (first round)
* Matteo Gigante (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 | Albert Ramos Viñolas | 3 | 3 | | | | |
| | Benjamin Hassan | 6 | 6 | | | | |
| | Benjamin Hassan | 6 | 6 | | Benjamin Hassan | 5 | 5 |
| | | | | 2 | Flavio Cobolli | 7 | 7 |
| | Franco Agamenone | 4 | 1 | 2 | Flavio Cobolli | 7 | 7 |
| 2 | Flavio Cobolli | 6 | 6 | | | | |

### 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 | A Ramos Viñolas | 6 | 3 | 6 | | | | | | | | | | | | |
| LL | H Laaksonen | 4 | 6 | 2 | 1 | A Ramos Viñolas | 7$^9$ | 6 | | | | | | | | |
| WC | G Elias | 6 | 6 | | WC | G Elias | 6$^7$ | 4 | | | | | | | | |
| | N Fatić | 2 | 2 | | | | | | 1 | A Ramos Viñolas | 6 | 6 | | | | |
| WC | J Sousa | 6 | 7 | | | | | | WC | J Sousa | 4 | 2 | | | | |
| LL | H Rocha | 2 | 5 | | WC | J Sousa | 6 | 6 | | | | | | | | |
| WC | P Sousa | 6 | 6 | | WC | P Sousa | 2 | 3 | | | | | | | | |
| 6 | T Droguet | 4 | 4 | | | | | | | | | | 1 | A Ramos Viñolas | 3 | 3 |
| 4 | P Llamas Ruiz | 6 | 6 | | | | | | | | | | | B Hassan | 6 | 6 |
| | A Giannessi | 3 | 1 | | 4 | P Llamas Ruiz | 4 | 6$^2$ | | | | | | | | |
| Q | J Barranco Cosano | 3 | 4 | | SE | O Roca Batalla | 6 | 7$^7$ | | | | | | | | |
| SE | O Roca Batalla | 6 | 6 | | | | | | SE | O Roca Batalla | 6$^1$ | 4 | | | | |
| Q | F Forti | 6 | 1 | 3 | | | | | | B Hassan | 7$^7$ | 6 | | | | |
| | B Hassan | 3 | 6 | 6 | | B Hassan | 7 | 6 | | | | | | | | |
| | G Blancaneaux | 4 | 2 | | 5 | I Gakhov | 5 | 1 | | | | | | | | |
| 5 | I Gakhov | 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 | Semifinals | Semifinals | Semifinals | Semifinals |
| 8 | M Gigante | 4 | 6$^4$ | | | | | | | | | | | | | | |
| | F Agamenone | 6 | 7$^7$ | | | F Agamenone | 7$^7$ | 6 | | | | | | | | | |
| | S Travaglia | 6 | 2 | 6$^1$ | Q | L Mikrut | 6$^4$ | 3 | | | | | | | | | |
| Q | L Mikrut | 1 | 6 | 7$^7$ | | | | | | | F Agamenone | 7$^7$ | 7 | | | | |
| | M Valkusz | 6 | 6$^4$ | 0$^r$ | | | | | | | R Bonadio | 6$^5$ | 5 | | | | |
| | Edoardo Lavagno | 3 | 7$^7$ | 0 | | E Lavagno | 6 | 3 | 2 | | | | | | | | |
| | R Bonadio | 6 | 6 | | | R Bonadio | 3 | 6 | 6 | | | | | | | | |
| 3 | T Skatov | 4 | 3 | | | | | | | | | | | | F Agamenone | 4 | 1 |
| 7 | Z Kolář | 4 | 3 | | | | | | | | | | | 2 | F Cobolli | 6 | 6 |
| | G-A Bailly | 6 | 6 | | | G-A Bailly | 5 | 7$^7$ | 1 | | | | | | | | |
| Q | Alexander Weis | 1 | 3 | | | C Hemery | 7 | 6$^4$ | 6 | | | | | | | | |
| | C Hemery | 6 | 6 | | | | | | | | C Hemery | 4 | 3 | | | | |
| Q | O Krutykh | 5 | 6 | 6 | | | | | | 2 | F Cobolli | 6 | 6 | | | | |
| | Gerard Campana Lee | 7 | 2 | 3 | Q | O Krutykh | 6$^2$ | 3 | | | | | | | | | |
| Q | E Dalla Valle | 4 | 7 | 0 | 2 | F Cobolli | 7$^7$ | 6 | | | | | | | | | |
| 2 | F Cobolli | 6 | 5 | 6 | | | | | | | | | | | | | |