| Champ: | Roger Federer |
| Runner: |  Milos Raonic |
| Score: | 6–4, 7–6(7–3) |
| Draw: | 28 (4 / 3) |
| Seeds: | 8 |
| Type: | singles doubles |
| Before Name: | Stuttgart Open – Singles |
| After Name: | Stuttgart Open – Singles |
| Main Name: | Stuttgart Open |
See main article: article and 2018 MercedesCup.
Lucas Pouille was the defending champion, but lost in the semifinals to Milos Raonic.
Roger Federer won his first title in Stuttgart, defeating Raonic in the final, 6–4, 7–6(7–3). By reaching the final, Federer regained the ATP no. 1 singles ranking. This was his record extending 18th Grass Court Title and his final ATP 250 title before retiring in 2022.
The top four seeds receive a bye into the second round.