2018 Porsche Tennis Grand Prix – Singles

Laura Siegemund was the defending champion, but lost in the second round to CoCo Vandeweghe.

Karolína Plíšková won the title, defeating Vandeweghe in the final, 7–6(7–2), 6–4.

15-year-old Marta Kostyuk became the youngest player to win a main draw match in Stuttgart since Martina Hingis in October 1994.

Seeds
The top four seeds received a bye into the second round. • #🇷🇴 Simona Halep (quarterfinals)

• #🇪🇸 Garbiñe Muguruza (second round, retired)

• #🇺🇦 Elina Svitolina (quarterfinals)

• # Jeļena Ostapenko (quarterfinals)

• #🇨🇿 Karolína Plíšková (champion)

• #🇫🇷 Caroline Garcia (semifinals)

• #🇺🇸 Sloane Stephens (first round)

• #🇨🇿 Petra Kvitová (first round)

Seeds
• #🇫🇷 Alizé Cornet (qualifying competition)

• #🇰🇿 Zarina Diyas (qualified)

• #🇩🇪 Carina Witthöft (qualifying competition, lucky loser)

• # Hsieh Su-wei (second round)

• #🇪🇪 Kaia Kanepi (qualifying competition)

• #🇨🇿 Markéta Vondroušová (qualified)

• #🇺🇸 Varvara Lepchenko (qualifying competition)

• # 🇺🇸 Bernarda Pera (first round)

Qualifiers
• # 🇺🇦 Marta Kostyuk

• # 🇰🇿 Zarina Diyas

• # 🇨🇿 Markéta Vondroušová

• # 🇷🇺 Veronika Kudermetova

Lucky loser
• # 🇩🇪 Carina Witthöft