See main article: 2018 Porsche Tennis Grand Prix.
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.[1]
The top four seeds received a bye into the second round.