Trail RunningUTMB Index Races

Trail Les 40 Bosses

Trail Running covering 10 km to 120 km with up to 4,900 m D+ in Saint-Leu-la-Forêt (Île-de-France, France)

LocationSaint-Leu-la-Forêt, Île-de-France, FranceShow on map(49.0177° N, 2.2454° E)
Date & StatusDecember 5, 2026 to December 6, 2026Date confirmed
Elevation gainUp to +4,900 m

Trail Les 40 Bosses is an endurance sporting event in Saint-Leu-la-Forêt, Île-de-France, FR focused on Trail Running. It is part of UTMB Index Races. Key features include Forest, Nature & Off-Road, Lakes & Ponds, Mountain.

The race program comprises 5 competitions, including Trail 120 km (120 km, +4,900 m D+), Trail 75 km (75 km, +3,000 m D+), Trail 45 km (45 km, +2,000 m D+), Trail 20 km (20 km, +850 m D+), and Trail 10 km (10 km, +400 m D+). The next edition is officially confirmed from December 5, 2026 to December 6, 2026. Official race regulations, course details, and registration information are provided on the organizer's website (les40bosses.fr).

Official website
Trail Les 40 Bosses in Saint-Leu-la-Forêt (Work: "Forêt de Fontainebleau-Les Rochers du Houx (DC n°7)-20170918", Photo: Daniel VILLAFRUELA, License: CC BY-SA 4.0, Source: Wikimedia Commons)
"Forêt de Fontainebleau-Les Rochers du Houx (DC n°7)-20170918" · Photo: Daniel VILLAFRUELA · Wikimedia CommonsCC BY-SA 4.0
Cropped to 16:9 (960 × 540 px), WebP · Shared under the same license

Event characteristics

ForestNature & Off-RoadLakes & PondsMountainHigh AltitudeIslandMulti-Day

Races & distances (5)

CompetitionDisciplineDistanceElevation gainAltitude rangeCourse typeCourse & profile
Trail 120 kmTrail Running120 km+4,900 m104 m - 2,162 mLoop courseRoute & profile
Trail 75 kmTrail Running75 km+3,000 m107 m - 1,367 mLoop courseRoute & profile
Trail 45 kmTrail Running45 km+2,000 m110 m - 950 mLoop courseRoute & profile
Trail 20 kmTrail Running20 km+850 m113 m - 470 mLoop courseRoute & profile
Trail 10 kmTrail Running10 km+400 m116 m - 284 mLoop courseRoute & profile
Course & Elevation Telemetry

Course route & map

Distance
120 km
Elevation gain
+4,900 m D+
Elevation loss
-4,900 m D-
Altitude range
104 m - 2,162 m
Gradient (Avg / Max)
8.2 % / 14.8 %
Course format
Loop course
120 km+4,900 m D+
Start (S)Finish (F)
N20406080100FS49.0178° N, 2.2454° E

Elevation profile & course telemetry

Altitude from 104 m to 2,162 m above sea level (+4,900 m D+, -4,900 m D-)

Peak: 2,162 m·at 61.5 km·Ø 8.2 %
104 m790 m1,476 m2,162 m0 km24 km48 km72 km96 km120 km2,162 m
Event Information & Answers

Frequently asked questions (FAQ)

When and where does Trail Les 40 Bosses take place?

Trail Les 40 Bosses takes place in Saint-Leu-la-Forêt, Île-de-France, FR (start area at coordinates 49.0177° N, 2.2454° E). The next edition is officially confirmed from December 5, 2026 to December 6, 2026.

What races and distances are offered at Trail Les 40 Bosses?

The race program comprises 5 competitions, including Trail 120 km (120 km, +4,900 m D+), Trail 75 km (75 km, +3,000 m D+), Trail 45 km (45 km, +2,000 m D+), Trail 20 km (20 km, +850 m D+), and Trail 10 km (10 km, +400 m D+). The competitions belong to Trail Running.

What is the course layout and elevation profile for Trail Les 40 Bosses?

The main competition (Trail 120 km over 120 km) is designed as a loop course featuring +4,900 m of elevation gain and -4,900 m of elevation loss, ranging between 104 m and 2,162 m above sea level. An interactive course map with route visualization, elevation profile, and GPX export is available in the course section on this page.

Where can I find registration and official race rules for Trail Les 40 Bosses?

Official race regulations, course details, and registration information are provided on the organizer's website (les40bosses.fr).