2018 US Open – Women's singles

Naomi Osaka defeated Serena Williams in the final, 6–2, 6–4 to win the women's singles tennis title at the 2018 US Open. It was her first major title, and she lost only one set en route (to Aryna Sabalenka in the fourth round). Osaka became the first Japanese player to win a major singles title. Following the win, Osaka made her top 10 rankings debut. Williams was attempting to equal Margaret Court's all-time record of 24 major singles titles, and to set a new Open Era record by winning a seventh US Open singles title.

Sloane Stephens was the defending champion, but lost to Anastasija Sevastova in the quarterfinals.

Simona Halep's first-round loss to Kaia Kanepi marked the first time in the Open Era that the top seed lost in the first round. The losses of Halep in the first round and second seed Caroline Wozniacki in the second round marked the first time that the top two seeds failed to reach the third round, and the second time this happened at any major in the Open Era (following the 2014 French Open).

This marked the final major appearance for former world No. 2 and 2015 WTA Finals champion Agnieszka Radwańska, who lost in the first round to Tatjana Maria.

Seeds
• 🇷🇴 Simona Halep (first round)

• Caroline Wozniacki (second round)

• 🇺🇸 Sloane Stephens (quarterfinals)

• 🇩🇪 Angelique Kerber (third round)

• 🇨🇿 Petra Kvitová (third round)

• 🇫🇷 Caroline Garcia (third round)

• 🇺🇦 Elina Svitolina (fourth round)

• 🇨🇿 Karolína Plíšková (quarterfinals)

• 🇩🇪 Julia Görges (second round)

•  Jeļena Ostapenko (third round)

• 🇷🇺 Daria Kasatkina (second round)

• 🇪🇸 Garbiñe Muguruza (second round)

•  Kiki Bertens (third round)

• 🇺🇸 Madison Keys (semifinals)

• 🇧🇪 Elise Mertens (fourth round)

• 🇺🇸 Venus Williams (third round)

• 🇺🇸 Serena Williams (final)

• 🇦🇺 Ashleigh Barty (fourth round)

•  Anastasija Sevastova (semifinals)

• 🇯🇵 Naomi Osaka (champion)

• 🇷🇴 Mihaela Buzărnescu (withdrew)

• 🇷🇺 Maria Sharapova (fourth round)

• 🇨🇿 Barbora Strýcová (third round)

• 🇺🇸 CoCo Vandeweghe (first round)

• 🇦🇺 Daria Gavrilova (second round)

• 🇧🇾 Aryna Sabalenka (fourth round)

• 🇷🇺 Anastasia Pavlyuchenkova (first round)

• 🇪🇪 Anett Kontaveit (first round)

• 🇸🇰 Dominika Cibulková (fourth round)

• 🇪🇸 Carla Suárez Navarro (quarterfinals)

• 🇸🇰 Magdaléna Rybáriková (first round)

•  Maria Sakkari (second round)