The 2021 Transylvania Open was a women's tennis tournament played on indoor hard courts.[1] It was the first edition of the Transylvania Open, and part of the WTA 250 series of the 2021 WTA Tour. It was held at the BT Arena in Cluj-Napoca, Romania, from 25 October until 31 October 2021. Second-seeded Anett Kontaveit won the singles title. By winning the title, Kontaveit qualified for the WTA Finals.[2]
See main article: 2021 Transylvania Open – Singles. 
Anett Kontaveit defeated 
Simona Halep, 6–2, 6–3
See main article: 2021 Transylvania Open – Doubles. Irina Bara / 
Ekaterine Gorgodze defeated 
Aleksandra Krunić / Lesley Pattinama Kerkhove, 4–6, 6–1, [11–9].
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Romania | Simona Halep | 19 | 1 | |
| Estonia | Anett Kontaveit | 20 | 2 | |
 United Kingdom | 24 | 3 | ||
| Jil Teichmann | 39 | 4 | ||
 Australia | Ajla Tomljanović | 43 | 5 | |
 Ukraine | Marta Kostyuk | 53 | 6 | |
| Romania | Irina-Camelia Begu | 56 | 7 | |
| Ukraine | Anhelina Kalinina | 57 | 8 |
The following players received wildcards into the main draw:
The following players received entry using a protected ranking:
The following players received entry from the qualifying draw:
The following player received entry as a lucky loser:
Ekaterina Alexandrova → replaced by Polona Hercog
Paula Badosa → replaced by Anna-Lena Friedsam
Alison Van Uytvanck Kaia Kanepi → replaced by Ivana Jorović Veronika Kudermetova → replaced by 
Bernarda Pera Elise Mertens → replaced by Elena-Gabriela Ruse
Camila Osorio → replaced by Jana Fett
Mayar Sherif → replaced by Mona Barthel| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
| United States | Kaitlyn Christian |  New Zealand | Erin Routliffe | 107 | 1 | |
| Serbia | Aleksandra Krunić | Lesley Pattinama Kerkhove | 123 | 2 | ||
| Romania | Monica Niculescu | Romania | Elena-Gabriela Ruse | 140 | 3 | |
 Kazakhstan | Anna Danilina |  Norway | Ulrikke Eikeri | 153 | 4 |
The following pairs received wildcards into the doubles main draw:
Sharon Fichman / 
Giuliana Olmos → replaced by Alena Fomina-Klotz / Ekaterina Yashina Ulrikke Eikeri / Catherine Harrison → replaced by Anna Danilina / Ulrikke Eikeri