| Champ: |  Dominic Thiem |
| Runner: |  Martin Kližan |
| Score: | 6–3, 6–1 |
| Draw: | 28 (4 / 3) |
| Seeds: | 8 |
| Type: | singles doubles |
See main article: article and 2018 St. Petersburg Open.
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.[1]
The top four seeds receive a bye into the second round.