Saturday, December 5, 2026
Distance
Climb
Terrain
Difficulty
Les 40 Bosses is a challenging trail running event in the forest of Île-de-France, featuring races from 10km to 120km with significant elevation gain. It is the toughest trail in the region and includes a UTMB 100M Qualifier.
120km course in two loops covering the entire massif
75km in a single loop on the first part of the 120km
Historic 45km with 2000m elevation gain
Classic 20km with 850m elevation gain
10km sprint to discover trail running
Start / Finish
Saint-Leu-la-Forêt (probable)
Saint-Leu-la-Forêt (probable)
Route
On the day
Before you enter
Other questions
Registrations for the 2026 edition opened on March 20, 2026 at 12:00.
Yes, for full races (20km and 45km) you can sign up on a waitlist. Invitations are sent by email and valid for 48 hours.
No, bib resale is not allowed. Any bib sold through other channels will be automatically cancelled.
The start and finish are likely at Saint-Leu-la-Forêt in the Montmorency forest.
Yes, the 120km is a UTMB 100M Qualifier.
Saint-Leu-la-Forêt, France
Saturday, December 5, 2026
More races like this one
€110
entry fee