2021 Porsche Tennis Grand Prix – Singles

Ashleigh Barty defeated Aryna Sabalenka in the final, 3–6, 6–0, 6–3 to win the women's singles tennis title at the 2021 Stuttgart Open. It marked her 11th career Women's Tennis Association (WTA) singles title and her second on clay. She became the first reigning world No. 1 to win the title since Justine Henin in 2007.

Petra Kvitová was the defending champion from when the tournament was last held in 2019, but lost in the quarterfinals to Elina Svitolina.

Seeds
The top four seeds received a bye into the second round. • #🇦🇺 Ashleigh Barty (champion)

• #🇷🇴 Simona Halep (semifinals)

• #🇺🇸 Sofia Kenin (second round)

• #🇺🇦 Elina Svitolina (semifinals)

• #🇧🇾 Aryna Sabalenka (final)

• #🇨🇿 Karolína Plíšková (quarterfinals)

• #🇨🇿 Petra Kvitová (quarterfinals)

• # Belinda Bencic (second round)

Seeds
• # 🇷🇺 Margarita Gasparyan (first round)

• # 🇷🇺 Varvara Gracheva (qualifying competition)

• # 🇨🇳 Wang Yafan (withdrew)

• # 🇩🇪 Anna-Lena Friedsam (qualified)

• # Stefanie Vögele (qualified)

• # 🇩🇪 Tamara Korpatsch (qualifying competition, lucky loser)

• # 🇩🇪 Mona Barthel (qualified)

• # Daniela Seguel (first round)

• # Jana Fett (first round)

• # Indy de Vroome (first round)

• # 🇩🇪 Antonia Lottner (first round)

• # 🇷🇴 Laura Ioana Paar (first round)

Qualifiers
• # 🇩🇪 Nastasja Schunk

• # 🇩🇪 Mona Barthel

• # 🇳🇴 Ulrikke Eikeri

• # 🇩🇪 Anna-Lena Friedsam

• # Stefanie Vögele

• # 🇩🇪 Julia Middendorf

Lucky losers
• # 🇩🇪 Tamara Korpatsch

• # Ekaterine Gorgodze