The 2021 WTA Romanian Open, known as the Winners Open due to sponsorship reasons, was a professional women's tennis tournament played on outdoor clay courts at the Winners Sports Club. It was the 1st edition of the tournament held in the city of Cluj-Napoca and was a part of the 2021 WTA Tour.[1]
See main article: 2021 Winners Open – Singles.
Mayar Sherif, 6–1, 6–1.This was Petkovic's seventh WTA Tour singles title, and first since 2015.
See main article: 2021 Winners Open – Doubles.
Natela Dzalamidze / Kaja Juvan def. 
Katarzyna Piter / Mayar Sherif, 6–3, 6–4.This was the maiden WTA Tour title won by both Dzalamidze and Juvan.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 France | Alizé Cornet | 63 | 1 | |
| Andrea Petkovic | 97 | 2 | ||
 Romania | Ana Bogdan | 101 | 3 | |
 Italy | Martina Trevisan | 102 | 4 | |
| Romania | Elena-Gabriela Ruse | 105 | 5 | |
| Kaja Juvan | 114 | 6 | ||
| Viktoriya Tomova | 119 | 7 | ||
 Slovakia | Kristína Kučová | 120 | 8 |
The following players received wildcards into the main draw:
The following player received entry using a protected ranking:
The following players received entry from the qualifying draw:
Tímea Babos → replaced by Katarzyna Kawa Irina-Camelia Begu → replaced by Viktória Kužmová Elisabetta Cocciaretto → replaced by Mihaela Buzărnescu
Zarina Diyas → replaced by Jaqueline Cristian Sara Errani → replaced by Kristína Kučová Mayar Sherif Anna Karolína Schmiedlová
Tereza Martincová → replaced by 
Lesia Tsurenko Jasmine Paolini → replaced by Réka Luca Jani
Çağla Büyükakçay Patricia Maria Țig → replaced by 
Lara Arruabarrena| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
| Slovakia | Viktória Kužmová | Poland | Alicja Rosolska | 140 | 1 | |
 Serbia | Aleksandra Krunić |  Belarus | Lidziya Marozava | 150 | 2 | |
| Spain | Lara Arruabarrena | Romania | Andreea Mitu | 186 | 3 | |
 Georgia | Oksana Kalashnikova | Slovakia | Tereza Mihalíková | 233 | 4 |
The following pairs received wildcards into the doubles main draw:
The following pair received entry using a protected ranking:
Irina-Camelia Begu / Andreea Mitu → replaced by Lara Arruabarrena / Andreea Mitu Anna Bondár / Fanny Stollár → replaced by Katarzyna Piter / Mayar Sherif Anna Danilina / 
Ulrikke Eikeri → replaced by Anna Bondár / Ulrikke Eikeri Viktória Kužmová / Arantxa Rus → replaced by Alena Fomina / Ekaterina Yashina Alicja Rosolska → replaced by Viktória Kužmová / Alicja Rosolska Ekaterine Gorgodze / Paula Kania-Choduń → replaced by Oana Georgeta Simion / Gabriela Talabă
