# 2021 İstanbul Cup – Singles

Sorana Cîrstea defeated Elise Mertens in the final, 6–1, 7–6$^{(7–3)}$ to win the women's singles tennis title at the 2021 İstanbul Cup. This was Cîrstea's first title since 2008. Cîrstea did not drop a set throughout the tournament.
Patricia Maria Țig was the defending champion, but she chose not to participate this year.

## Seeds

* Elise Mertens (final)
* Petra Martić (first round)
* Veronika Kudermetova (semifinals)
* Daria Kasatkina (second round)
* Barbora Krejčíková (second round)
* Anastasia Pavlyuchenkova (first round)
* Zheng Saisai (withdrew)
* Wang Qiang (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 | Final |
| 1/WC | Elise Mertens | 6 | 6 | | | | |
| 3 | Veronika Kudermetova | 1 | 4 | | | | |
| 3 | Veronika Kudermetova | 1 | 4 | 1/WC | Elise Mertens | 1 | 6$^3$ |
| | | | | | Sorana Cîrstea | 6 | 7$^7$ |
| | Marta Kostyuk | 4 | 4 | | Sorana Cîrstea | 6 | 7$^7$ |
| | Sorana Cîrstea | 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 | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1/WC | E Mertens | 6 | 6 | | | | | | | | | | | | | | | |
| Q | L Arruabarrena | 2 | 0 | | 1/WC | E Mertens | 6 | 4 | 6 | | | | | | | | | |
| Q | N Párrizas Díaz | 4 | 6 | 3 | | V Golubic | 4 | 6 | 1 | | | | | | | | | |
| | V Golubic | 6 | 2 | 6 | | | | | | 1/WC | E Mertens | 6 | 6 | | | | | |
| | K Siniaková | 7$^7$ | 3 | 6 | | | | | | | K Siniaková | 4 | 4 | | | | | |
| Q | C Bucșa | 6$^5$ | 6 | 3 | | K Siniaková | 6 | 3 | 6 | | | | | | | | | |
| | K Mladenovic | 6 | 6 | | | K Mladenovic | 4 | 6 | 4 | | | | | | | | | |
| LL | B Haas | 4 | 3 | | | | | | | | | | | | 1/WC | E Mertens | 6 | 6 |
| 3 | V Kudermetova | 6 | 3 | 7$^7$ | | | | | | | | | | | 3 | V Kudermetova | 1 | 4 |
| | B Pera | 4 | 6 | 6$^4$ | 3 | V Kudermetova | 6 | 6 | | | | | | | | | | |
| | Z Diyas | 4 | 4 | | | K Kanepi | 4 | 3 | | | | | | | | | | |
| | K Kanepi | 6 | 6 | | | | | | | 3 | V Kudermetova | 2 | 6 | 6 | | | | |
| | N Hibino | 3 | 3 | | | | | | | | A Bogdan | 6 | 3 | 3 | | | | |
| | A Bogdan | 6 | 6 | | | A Bogdan | 6 | 6 | | | | | | | | | | |
| WC | Ç Büyükakçay | 7$^{10}$ | 2 | 0 | 5 | B Krejčíková | 3 | 3 | | | | | | | | | | |
| 5 | B Krejčíková | 6$^8$ | 6 | 6 | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals |
| 8 | Q Wang | 4 | 6 | 6 | | | | | | | | | | | | |
| Q | A Gasanova | 6 | 1 | 2 | 8 | Q Wang | 1 | 4 | | | | | | | | |
| WC | A Konjuh | 7 | 6 | | WC | A Konjuh | 6 | 6 | | | | | | | | |
| | S Errani | 5 | 2 | | | | | | WC | A Konjuh | 5 | 6 | 3 | | | |
| Q | K Rakhimova | 4 | 3 | | | | | | | M Kostyuk | 7 | 4 | 6 | | | |
| | M Kostyuk | 6 | 6 | | | M Kostyuk | 6 | 7 | | | | | | | | |
| Q | T Mrdeža | 1 | 0 | | 4 | D Kasatkina | 3 | 5 | | | | | | | | |
| 4 | D Kasatkina | 6 | 6 | | | | | | | | | | | M Kostyuk | 4 | 4 |
| 6 | A Pavlyuchenkova | 6$^2$ | 7$^{10}$ | 4 | | | | | | | | | | S Cîrstea | 6 | 6 |
| | A Potapova | 7$^7$ | 6$^8$ | 6 | | A Potapova | 6$^6$ | 4 | | | | | | | | |
| | K Kozlova | 4 | 6$^6$ | | | S Cîrstea | 7$^8$ | 6 | | | | | | | | |
| | S Cîrstea | 6 | 7$^8$ | | | | | | | S Cîrstea | 6 | 0 | | | | |
| WC | V Zvonareva | 6 | 6 | | | | | | | F Ferro | 4 | 0$^r$ | | | | |
| | P Hercog | 3 | 3 | | WC | V Zvonareva | 3 | 3 | | | | | | | | |
| | F Ferro | 7 | 6 | | | F Ferro | 6 | 6 | | | | | | | | |
| 2 | P Martić | 5 | 2 | | | | | | | | | | | | | |

## Qualifying
### Seeds

* Océane Dodin (first round)
* Kamilla Rakhimova (qualified)
* Jaqueline Cristian (qualifying competition)
* Leonie Küng (first round)
* Barbara Haas (qualifying competition, lucky loser)
* Harmony Tan (qualifying competition)
* Nuria Párrizas Díaz (qualified)
* Cristina Bucșa (qualified)
* Lara Arruabarrena (qualified)
* Anastasia Gasanova (qualified)
* Mariam Bolkvadze (qualifying competition)
* Liang En-shuo (first round)

### Qualifiers

* Tereza Mrdeža
* Kamilla Rakhimova
* Cristina Bucșa
* Anastasia Gasanova
* Nuria Párrizas Díaz
* Lara Arruabarrena

### Lucky loser

* Barbara Haas

### Draw
#### First qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition |
| 1 | Océane Dodin | 6$^3$ | 6 | 0 | | | |
| | Tereza Mrdeža | 7$^7$ | 3 | 6 | | | |
| | Tereza Mrdeža | 7$^7$ | 3 | 6 | Tereza Mrdeža | 6 | 6 |
| | | | | | Irene Burillo Escorihuela | 4 | 2 |
| | Irene Burillo Escorihuela | 6 | 6 | | Irene Burillo Escorihuela | 4 | 2 |
| 12 | Liang En-shuo | 1 | 4 | | | | |

#### Second qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 2 | Kamilla Rakhimova | 6 | 1 | 6 | | | | |
| | Tessah Andrianjafitrimo | 2 | 6 | 1 | | | | |
| | Tessah Andrianjafitrimo | 2 | 6 | 1 | 2 | Kamilla Rakhimova | 6 | 6 |
| | | | | | 11 | Mariam Bolkvadze | 4 | 3 |
| | Yuliya Hatouka | 4 | 4 | | 11 | Mariam Bolkvadze | 4 | 3 |
| 11 | Mariam Bolkvadze | 6 | 6 | | | | | |

#### Third qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 3 | Jaqueline Cristian | 6 | 6 | | | | |
| | Pemra Özgen | 4 | 3 | | | | |
| | Pemra Özgen | 4 | 3 | 3 | Jaqueline Cristian | 1 | 3 |
| | | | | 8 | Cristina Bucșa | 6 | 6 |
| | Dalila Jakupović | 1 | 2 | 8 | Cristina Bucșa | 6 | 6 |
| 8 | Cristina Bucșa | 6 | 6 | | | | |

#### Fourth qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 4 | Leonie Küng | 3 | 6 | 3 | | | | | |
| WC | Nikola Bartůňková | 6 | 4 | 6 | | | | | |
| WC | Nikola Bartůňková | 6 | 4 | 6 | WC | Nikola Bartůňková | 4 | 7 | 3 |
| | | | | | 10 | Anastasia Gasanova | 6 | 5 | 6 |
| | Irina Fetecău | 2 | 3 | | 10 | Anastasia Gasanova | 6 | 5 | 6 |
| 10 | Anastasia Gasanova | 6 | 6 | | | | | | |

#### Fifth qualifier

| First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 5 | Barbara Haas | 6 | 7 | | | | | |
| WC | Zeynep Sönmez | 3 | 5 | | | | | |
| WC | Zeynep Sönmez | 3 | 5 | 5 | Barbara Haas | 6 | 1 | 0 |
| | | | | 7 | Nuria Párrizas Díaz | 2 | 6 | 6 |
| WC | İpek Öz | 3 | 4 | 7 | Nuria Párrizas Díaz | 2 | 6 | 6 |
| 7 | Nuria Párrizas Díaz | 6 | 6 | | | | | |

#### Sixth qualifier

| First round | First round | First round | First round | First round | Qualifying competition | Qualifying competition | Qualifying competition | Qualifying competition |
| 6 | Harmony Tan | 6$^1$ | 6 | 6 | | | | |
| | Dalma Gálfi | 7$^7$ | 3 | 1 | | | | |
| | Dalma Gálfi | 7$^7$ | 3 | 1 | 6 | Harmony Tan | 3 | 3 |
| | | | | | 9 | Lara Arruabarrena | 6 | 6 |
| WC | Berfu Cengiz | 5 | 3 | | 9 | Lara Arruabarrena | 6 | 6 |
| 9 | Lara Arruabarrena | 7 | 6 | | | | | |