2021 Thoreau Tennis Open – Singles

Caroline Dolehide was the defending champion, having won the previous edition in 2019. She lost in the second round to Katrina Scott.

Magdalena Fręch won the title, defeating Renata Zarazúa in the final, 6–3, 7–6(7–4).

Seeds
• # 🇧🇪 Alison Van Uytvanck (withdrew)

• # Hsieh Su-wei (quarterfinals)

• # 🇺🇸 Madison Brengle (semifinals)

• # 🇷🇺 Vera Zvonareva (semifinals)

• # 🇺🇸 Lauren Davis (first round)

• # 🇺🇸 Christina McHale (first round)

• # 🇧🇪 Greet Minnen (second round)

• # 🇲🇽 Renata Zarazúa (final)

• # 🇦🇺 Storm Sanders (second round)

Seeds
• # Mariam Bolkvadze (qualified)

• #🇧🇷 Beatriz Haddad Maia (moved to main draw)

• #🇺🇦 Kateryna Bondarenko (first round)

• #🇺🇸 Robin Anderson (qualified)

• #🇩🇪 Mona Barthel (first round)

• #🇺🇸 Whitney Osuigwe (first round)

• #🇬🇧 Samantha Murray Sharan (qualifying competition)

• # Liang En-shuo (qualified)

Qualifiers
• # Mariam Bolkvadze

• #🇺🇸 Victoria Duval

• # Liang En-shuo

• #🇺🇸 Robin Anderson

Lucky loser
• #🇺🇸 Alexa Glatch