Course
Marathon42.2 km
Half Marathon21.1 km
10K10 km
5K5 km
Key dates
- ★Race daySun 6 Dec 2026
Date confirmed with the organiser · entry window checked by RunCalendar
About
Les 40 bosses is a challenging trail running event in the forests of Île-de-France, France. The event offers several race distances, including a grueling 120km course with 5,500m of elevation gain.
Your next race, seen from above.
Save Les 40 Bosses to your season and RunCalendar reminds you the morning entries open and before they close. Free on iPhone, no account needed.
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Save Les 40 Bosses to your season and RunCalendar reminds you the morning entries open and before they close. Free on iPhone, no account needed.
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Essec Night Run
Passes Cergy-Pontoise's Axe Majeur landmark at night
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A confirmed date shows its day; a provisional one shows only its month, because we won't claim a day we don't have. This page is rebuilt every night from the RunCalendar catalogue.