2018 St. Petersburg Open – Singles

Damir Džumhur was the defending champion, but lost in the quarterfinals to Stan Wawrinka.

Dominic Thiem won the title after defeating Martin Kližan 6–3, 6–1 in the final. Notably, this was Kližan's first defeat in a deciding match, after 10 consecutive titles at ATP World Tour level.

The tournament marked the last appearance of Mikhail Youzhny in professional tennis.

Seeds
The top four seeds receive a bye into the second round. • #🇦🇹 Dominic Thiem (champion)

• #🇮🇹 Fabio Fognini (second round)

• #🇮🇹 Marco Cecchinato (quarterfinals)

• #🇷🇺 Karen Khachanov (second round)

• #🇪🇸 Roberto Bautista Agut (semifinals)

• #🇧🇦 Damir Džumhur (quarterfinals)

• #🇨🇦 Denis Shapovalov (quarterfinals)

• #🇷🇺 Daniil Medvedev (quarterfinals)

Seeds
• # 🇮🇹 Lorenzo Sonego (first round)

• # 🇧🇾 Ilya Ivashka (qualified)

• # 🇧🇪 Ruben Bemelmans (qualifying competition, lucky loser)

• # 🇷🇸 Viktor Troicki (first round)

• # 🇪🇸 Adrián Menéndez Maceiras (qualified)

• # 🇫🇷 Stéphane Robert (first round)

• # 🇮🇹 Luca Vanni (qualified)

• # 🇷🇺 Alexey Vatutin (first round)

Qualifiers
• # 🇮🇹 Luca Vanni

• # 🇧🇾 Ilya Ivashka

• # 🇪🇸 Adrián Menéndez Maceiras

• # 🇦🇹 Lucas Miedler

Lucky loser
• # 🇧🇪 Ruben Bemelmans