This was the first edition of the event. Kurumi Nara won the title, defeating Klára Zakopalová in the final, 6–1, 4–6, 6–1.
Monica Niculescu was the defending champion, but retired in the quarterfinals against Carla Suárez Navarro.
Klára Zakopalová won the title, defeating Garbiñe Muguruza in the final, 4–6, 7–5, 6–0.
Elina Svitolina was the defending champion, and successfully defended her title, defeating Bojana Jovanovski in the final 6–1, 7–6(7–2).
Agnieszka Radwańska was the defending champion, but lost to Varvara Lepchenko in the quarterfinals.
Heather Watson was the defending champion, but lost to Polona Hercog in the first round.
Laura Siegemund was the defending champion, but could not defend her title due to a right knee injury.
Christina McHale was the defending champion, but lost in the semifinals to Zarina Diyas.
Markéta Vondroušová was the defending champion, but lost in the second round to Elise Mertens.
Elina Svitolina was the defending champion, but chose to compete in Stuttgart instead.
Anastasia Pavlyuchenkova was the defending champion, but chose not to participate.
Irina-Camelia Begu and Raluca Olaru were the defending champions, but chose not to participate together. Olaru played alongside Mihaela Buzărnescu, but lost in the semifinals to Danka Kovinić and Maryna Zanevska. Begu teamed up with Andreea Mitu and successfully defended the title, defeating Kovinić and Zanevska in the final, 6–3, 6–4.
Jessica Moore and Jocelyn Rae were the defending champions, however Rae retired from professional tennis in December 2017, while Moore decided not to participate.
Belinda Bencic was the champion the last time the event was held in 2017, but chose to compete in St. Petersburg instead.
Simona Halep won her first Italian Open title, after the defending champion Karolína Plíšková retired from the final, with the scoreline at 6–0, 2–1.
Aryna Sabalenka defeated Ashleigh Barty in the final, 6–0, 3–6, 6–4, to win the women's singles tennis title at the 2021 Madrid Open. It was Sabalenka's 10th career WTA Tour singles title and her first title on clay.
Barbora Krejčíková and Kateřina Siniaková defeated Gabriela Dabrowski and Demi Schuurs in the final, 6–4, 6–3, to win the women's doubles tennis title at the 2021 Madrid Open. It marked the second-seeded duo's first victory in Madrid and their seventh career WTA Tour doubles title together, as well as Krejčíková's eighth individual doubles title and Siniaková's 10th. Dabrowski and Schuurs were competing as a first-time pairing and bidding to win their first title at the tournament; Dabrowski was also aiming for her 10th doubles title and Schuurs, her 15th.
Barbora Krejčíková and Kateřina Siniaková defeated Bethanie Mattek-Sands and Iga Świątek in the final, 6–4, 6–2, to win the women's doubles tennis title at the 2021 French Open. It was the pair's second French Open title and third major together. Krejčíková became the first woman to win both the singles and doubles tournaments at a Grand Slam since Serena Williams at the 2016 Wimbledon Championships, and the first to do so at the French Open since Mary Pierce in 2000, making her the seventh woman to accomplish the sweep in French Open history.
Defending champion Hsieh Su-wei and her partner, Elise Mertens, defeated Veronika Kudermetova and Elena Vesnina in the final, 3–6, 7–5, 9–7, to win the ladies' doubles tennis title at the 2021 Wimbledon Championships. The pair saved two championship points in the final en route to winning their first major together.
This was the first edition of the tournament.
Anna Bondár was the defending champion but chose not to participate.
Misaki Doi 
Natalia Vikhlyantseva 
Alexa Guarachi 
Danka Kovinić 
