# 2021 Porto Open – Singles

This was the first edition of the tournament.
Altuğ Çelikbilek won the title after defeating Quentin Halys 6–2, 6–1 in the final.

## Seeds

* Thiago Seyboth Wild (second round)
* Prajnesh Gunneswaran (second round)
* Emilio Gómez (semifinals)
* Alejandro Tabilo (first round)
* Frederico Ferreira Silva (second round, retired)
* Go Soeda (first round)
* Thanasi Kokkinakis (second round)
* Denis Istomin (second 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 |
| | Altuğ Çelikbilek | 6 | 6 | | | |
| | Sergiy Stakhovsky | 2 | 1 | | | |
| | Sergiy Stakhovsky | 2 | 1 | Altuğ Çelikbilek | 6 | 6 |
| | | | | Quentin Halys | 2 | 1 |
| 3 | Emilio Gómez | 4 | 4 | Quentin Halys | 2 | 1 |
| | Quentin Halys | 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 |
| 1 | T Seyboth Wild | 6 | 6 | | | | | | | | | | | | | |
| | R Olivo | 4 | 2 | | 1 | T Seyboth Wild | 6$^5$ | 3 | | | | | | | | |
| | A Çelikbilek | 6 | 6$^5$ | 6 | | A Çelikbilek | 7$^7$ | 6 | | | | | | | | |
| Q | Yo Watanuki | 3 | 7$^7$ | 3 | | | | | | | A Çelikbilek | 7 | 6 | | | |
| | T Ito | 6 | 6 | | | | | | | | T Ito | 5 | 3 | | | |
| LL | Luís Faria | 0 | 2 | | | T Ito | 6 | 1 | | | | | | | | |
| | L Giustino | 4 | 6 | 3 | 5 | F Ferreira Silva | 4 | 0$^r$ | | | | | | | | |
| 5 | F Ferreira Silva | 6 | 4 | 6 | | | | | | | | | | A Çelikbilek | 6 | 6 |
| 4 | A Tabilo | 6 | 1 | 2 | | | | | | | | | | S Stakhovsky | 2 | 1 |
| Alt | P Polansky | 1 | 6 | 6 | Alt | P Polansky | 6$^3$ | 4 | | | | | | | | |
| WC | G Oliveira | 6 | 6 | | WC | G Oliveira | 7$^7$ | 6 | | | | | | | | |
| WC | N Borges | 1 | 2 | | | | | | | WC | G Oliveira | 6$^2$ | 6$^5$ | | | |
| | R Cid Subervi | 1 | 1$^r$ | | | | | | | | S Stakhovsky | 7$^7$ | 7$^7$ | | | |
| Alt | M Viola | 6 | 4 | | Alt | M Viola | 2 | 6 | 5 | | | | | | | |
| | S Stakhovsky | 2 | 6 | 7$^7$ | | S Stakhovsky | 6 | 4 | 7 | | | | | | | |
| 6 | G Soeda | 6 | 2 | 6$^5$ | | | | | | | | | | | | |

### 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 |
| 8 | D Istomin | 6 | 6 | | | | | | | | | | | | | | |
| | G Andreozzi | 4 | 3 | | 8 | D Istomin | 5 | 4 | | | | | | | | | |
| Q | S Verbeek | 7$^9$ | 4 | 1 | WC | G Elias | 7 | 6 | | | | | | | | | |
| WC | G Elias | 6$^7$ | 6 | 6 | | | | | | WC | G Elias | 3 | 6$^4$ | | | | |
| Q | G Blancaneaux | 6$^5$ | 6 | 6 | | | | | | 3 | E Gómez | 6 | 7$^7$ | | | | |
| | J Domingues | 7$^7$ | 2 | 4 | Q | G Blancaneaux | 1 | 7$^9$ | 1 | | | | | | | | |
| Alt | N Kuhn | 5 | 2 | | 3 | E Gómez | 6 | 6$^7$ | 6 | | | | | | | | |
| 3 | E Gómez | 7 | 6 | | | | | | | | | | | 3 | E Gómez | 4 | 4 |
| 7 | T Kokkinakis | 7$^7$ | 6 | | | | | | | | | | | | Q Halys | 6 | 6 |
| | R Marcora | 6$^3$ | 1 | | 7 | T Kokkinakis | 6$^5$ | 4 | | | | | | | | | |
| Q | U Blanch | 3 | 6 | 1 | | Q Halys | 7$^7$ | 6 | | | | | | | | | |
| | Q Halys | 6 | 3 | 6 | | | | | | | Q Halys | 6 | 6 | | | | |
| | M Janvier | 5 | 6 | 6$^5$ | | | | | | | S Diez | 3 | 0 | | | | |
| | S Diez | 7 | 2 | 7$^7$ | | S Diez | 6 | 1 | 6 | | | | | | | | |
| | M Bourgue | 2 | 6 | 1 | 2 | P Gunneswaran | 3 | 6 | 4 | | | | | | | | |
| 2 | P Gunneswaran | 6 | 3 | 6 | | | | | | | | | | | | | |