Mont-Blanc 42K is the 42.0km trail race at Mont-Blanc Marathon 2027 (Chamonix, France). The race starts on June 27, 2027.
Hold a steady pace and save energy for every section.
The course climbs 2540m+. With 60m/km of climbing, this is a true mountain course with sustained climbs and descents. By gradient, 43% of the distance is uphill, 41% downhill and 16% flat. The longest climb runs 6.8km at an average 13.8% grade (942m of vertical). The longest descent runs 7.0km at an average 13.0% grade (911m of vertical). The steepest climb averages 29.2% over 0.8km. The steepest descent drops at 32.8% over 0.3km. Surface: 84% trail, 10% road, and 6% smooth.
The highest summit on the course is Aiguillette des Posettes (2201m), 17.1km from the start. Other named summits along the route: Le Béchar (1720m).
Poles bring little benefit here: only about 9.0km of pole-friendly terrain.
Quad damage risk is moderate (index 33 of 100), with 45% of the load in the first half: 1 descent deserves a plan and a couple of downhill sessions before race day.
This page has a pacing and nutrition planner, a gradient matrix, an interactive elevation profile and historical weather for Mont-Blanc 42K.
Other distances of Mont-Blanc Marathon 2027Mont-Blanc 23K (23.0km)·Mont-Blanc 10K (10.0km)·Mont-Blanc KM Vertical (3.8km)
Other editions of Mont-Blanc 42K2026
Official websitewww.marathonmontblanc.fr/en