# 2021 Portugal Ladies Open – Singles

Isabella Shinikova was the defending champion but chose to compete at the 2021 BGL Luxembourg Open instead.
Zheng Saisai won the title, defeating Harmony Tan in the final, 6–4, 3–6, 6–3.

## Seeds

* Zheng Saisai
* Wang Xinyu (quarterfinals)
* Harmony Tan (final)
* Maddison Inglis (semifinals)
* Arina Rodionova (first round)
* Lizette Cabrera (first round)
* Beatriz Haddad Maia (semifinals)
* Daria Snigur (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 | Final |
| 1 | Zheng Saisai | 6 | 6 | | | | | |
| 4 | Maddison Inglis | 2 | 3 | | | | | |
| 4 | Maddison Inglis | 2 | 3 | 1 | Zheng Saisai | 6 | 3 | 6 |
| | | | | 3 | Harmony Tan | 4 | 6 | 3 |
| 3 | Harmony Tan | 7$^7$ | 7$^7$ | 3 | Harmony Tan | 4 | 6 | 3 |
| 7 | Beatriz Haddad Maia | 6$^5$ | 6$^4$ | | | | | |

### 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 | S Zheng | 6 | 6 | | | | | | | | | | | | | | | |
| | K Okamura | 2 | 1 | | 1 | S Zheng | 2 | 7 | 7 | | | | | | | | | |
| | A Hesse | 6 | 6 | | | A Hesse | 6 | 5 | 5 | | | | | | | | | |
| | C Monnet | 1 | 4 | | | | | | | 1 | S Zheng | 6 | 6 | | | | | |
| | M Benoît | 6 | 6 | | | | | | | | M Benoît | 3 | 1 | | | | | |
| WC | S Lança | 2 | 0 | | | M Benoît | 4 | 6 | 6 | | | | | | | | | |
| Q | IL Roșca | 4 | 6 | 7$^7$ | Q | IL Roșca | 6 | 4 | 4 | | | | | | | | | |
| 6 | L Cabrera | 6 | 3 | 6$^4$ | | | | | | | | | | | 1 | S Zheng | 6 | 6 |
| 4 | M Inglis | 3 | 7 | 6 | | | | | | | | | | | 4 | M Inglis | 2 | 3 |
| Q | W Falkowska | 6 | 5 | 3 | 4 | M Inglis | 6 | 6 | | | | | | | | | | |
| | R Anderson | 7$^7$ | 3 | 5 | | N Stevanović | 2 | 1 | | | | | | | | | | |
| | N Stevanović | 6$^3$ | 6 | 7 | | | | | | 4 | M Inglis | 6 | 4 | 6 | | | | |
| Q | O Gadecki | 4 | 6 | 6 | | | | | | SE | A Kulikova | 2 | 6 | 3 | | | | |
| WC | D Spiteri | 6 | 1 | 1 | Q | O Gadecki | 6 | 4 | 4 | | | | | | | | | |
| SE | A Kulikova | 6 | 6 | | SE | A Kulikova | 2 | 6 | 6 | | | | | | | | | |
| 5 | Ar Rodionova | 0 | 4 | | | | | | | | | | | | | | | |

### Bottom 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 |
| 8/JE | D Snigur | 3 | 4 | | | | | | | | | | | | | |
| | J Ponchet | 6 | 6 | | | J Ponchet | 5 | 4 | | | | | | | | |
| WC | I Murta | 3 | 3 | | Q | R Șerban | 7 | 6 | | | | | | | | |
| Q | R Șerban | 6 | 6 | | | | | | Q | R Șerban | 6$^4$ | 5 | | | | |
| WC | F Jorge | 6 | 6$^6$ | 6 | | | | | 3 | H Tan | 7$^7$ | 7 | | | | |
| | C Alves | 2 | 7$^8$ | 2 | WC | F Jorge | 2 | 2 | | | | | | | | |
| Q | S Djoubri | 3 | 3 | | 3 | H Tan | 6 | 6 | | | | | | | | |
| 3 | H Tan | 6 | 6 | | | | | | | | | | 3 | H Tan | 7$^7$ | 7$^7$ |
| 7 | B Haddad Maia | 6 | 6 | | | | | | | | | | 7 | B Haddad Maia | 6$^5$ | 6$^4$ |
| Q | E Silva | 0 | 1 | | 7 | B Haddad Maia | 6 | 6 | | | | | | | | |
| | E Perez | 6 | 6 | | | E Perez | 4 | 4 | | | | | | | | |
| Q | S-R Sekulic | 2 | 2 | | | | | | 7 | B Haddad Maia | 6 | 6 | | | | |
| | T Maria | 6 | 6 | | | | | | 2 | Xin Wang | 3 | 4 | | | | |
| Q | E Bogdan | 2 | 4 | | | T Maria | 2 | 1 | | | | | | | | |
| | A Tikhonova | 3 | 5 | | 2 | Xin Wang | 6 | 6 | | | | | | | | |
| 2 | Xin Wang | 6 | 7 | | | | | | | | | | | | | |