The 2018 Open Harmonie mutuelle was a professional tennis tournament played on hard courts. It was the fifteenth edition of the tournament which was part of the 2018 ATP Challenger Tour. It took place in Saint-Brieuc, France between 26 March and 1 April 2018.
Singles main-draw entrants
Seeds
Rankings are as of 19 March 2018.
Other entrants
The following players received wildcards into the singles main draw: Evan Furness Manuel Guinard Antoine Hoang Ugo Humbert
The following players received entry into the singles main draw as special exempts: Grégoire Barrère Maxime Janvier
The following players received entry from the qualifying draw: Joris De Loore Laurynas Grigelis Tristan Lamasine Constant Lestienne
Champions
Singles
Ričardas Berankis def. Constant Lestienne 6–2, 5–7, 6–4.
Doubles
Sander Arends / Tristan-Samuel Weissborn def. Luke Bambridge / Joe Salisbury 4–6, 6–1, [10–7].