2018 Citi Open – Women's singles

Ekaterina Makarova was the defending champion, but lost in the first round to Ana Bogdan.

Svetlana Kuznetsova won the title, beating Donna Vekić in the final, 4–6, 7–6(9–7), 6–2, despite being four match points down in the second set.

Seeds
• # Caroline Wozniacki (withdrew due to leg injury)

• # 🇺🇸 Sloane Stephens (second round)

• # 🇯🇵 Naomi Osaka (second round)

• # 🇷🇺 Ekaterina Makarova (first round)

• # 🇷🇸 Aleksandra Krunić (first round)

• # Belinda Bencic (quarterfinals)

• # Donna Vekić (final)

• # 🇰🇿 Yulia Putintseva (quarterfinals)

Seeds
• # 🇧🇪 Ysaline Bonaventure (qualifying competition, lucky loser)

• # 🇺🇦 Anhelina Kalinina (qualified)

• # 🇷🇺 Sofya Zhuk (qualified)

• # 🇬🇧 Harriet Dart (qualified)

• # 🇺🇸 Francesca Di Lorenzo (first round)

• # 🇯🇵 Mayo Hibi (qualifying competition, lucky loser)

• # 🇺🇸 Allie Kiick (qualified)

• # 🇺🇸 Lauren Davis (first round)

Qualifiers
• # 🇺🇸 Allie Kiick

• # 🇺🇦 Anhelina Kalinina

• # 🇷🇺 Sofya Zhuk

• # 🇬🇧 Harriet Dart

Lucky losers
• # 🇯🇵 Mayo Hibi

• # 🇧🇪 Ysaline Bonaventure