2018 Mutua Madrid Open – Women's singles

Petra Kvitová defeated Kiki Bertens in the final, 7–6(8–6), 4–6, 6–3 to win the women's singles tennis title at the 2018 Madrid Open. It was Kvitová's third Madrid Open title, and she became the first player to win three women's singles titles at the Madrid Open.

Simona Halep was the two-time defending champion, but lost to Karolína Plíšková in the quarterfinals.

Halep and Caroline Wozniacki were in contention for the WTA no. 1 singles ranking at the beginning of the tournament. Halep retained the top ranking when Wozniacki lost to Bertens in the third round.

Seeds
• 🇷🇴 Simona Halep (quarterfinals)

• Caroline Wozniacki (third round)

• 🇪🇸 Garbiñe Muguruza (third round)

• 🇺🇦 Elina Svitolina (second round)

•  Jeļena Ostapenko (first round)

• 🇨🇿 Karolína Plíšková (semifinals)

• 🇫🇷 Caroline Garcia (semifinals)

• 🇺🇸 Venus Williams (first round)

• 🇺🇸 Sloane Stephens (third round)

• 🇨🇿 Petra Kvitová (champion)

• 🇩🇪 Julia Görges (third round)

• 🇺🇸 CoCo Vandeweghe (first round)

• 🇺🇸 Madison Keys (first round)

• 🇷🇺 Daria Kasatkina (quarterfinals)

•  Anastasija Sevastova (second round)

• 🇸🇰 Magdaléna Rybáriková (first round)

Seeds
• # 🇺🇸 Danielle Collins (qualified)

• # 🇧🇾 Aryna Sabalenka (qualified)

• # Hsieh Su-wei (withdrew, still playing in Rabat)

• # Polona Hercog (first round)

• # 🇧🇷 Beatriz Haddad Maia (first round)

• # 🇩🇪 Mona Barthel (qualifying competition, retired)

• # 🇷🇴 Ana Bogdan (qualifying competition)

• # 🇵🇱 Magda Linette (qualifying competition)

• # 🇧🇪 Kirsten Flipkens (qualifying competition)

• # 🇨🇿 Kristýna Plíšková (qualified)

• # 🇺🇦 Kateryna Bondarenko (first round)

• # 🇺🇸 Sachia Vickery (qualifying competition)

• # 🇺🇸 Jennifer Brady (first round)

• # 🇸🇪 Johanna Larsson (qualifying competition)

• # 🇷🇺 Natalia Vikhlyantseva (qualified)

• # 🇸🇰 Anna Karolína Schmiedlová (qualified)

Qualifiers
• # 🇺🇸 Danielle Collins

• # 🇧🇾 Aryna Sabalenka

• # 🇸🇰 Anna Karolína Schmiedlová

• # 🇺🇸 Bernarda Pera

• # 🇮🇹 Sara Errani

• # 🇪🇸 Sílvia Soler Espinosa

• # 🇨🇿 Kristýna Plíšková

• # 🇷🇺 Natalia Vikhlyantseva