Marathon du Mont-Blanc

Course & Elevation

The 42 km du Mont-Blanc is a trail marathon through the Chamonix valley and the main race of the Marathon du Mont-Blanc, a four-day trail festival held in late June. The Club des Sports de Chamonix, a non-profit association founded in 1905, organises the event. It began as the Cross du Mont-Blanc on 1 July 1979 with 450 participants, and it became the Marathon du Mont-Blanc in 2003, when the 42 km was added to the 23 km. The 42 km is run on the Sunday, covers 42 km with about 2,540 m of climbing and finishes in Chamonix. The organisers describe a fast, runnable first section followed by the steep, technical slopes of the Aiguillette des Posettes, with views of the Mont-Blanc range. Aid stations stand at Le Tour (km 13.5), Vallorcine (km 23.5) and La Flégère (km 34.2), plus one at the finish. Cut-offs are counted from the start of the last wave: 2 hours 45 at Le Tour, 5 hours 30 at Vallorcine and 8 hours 30 at La Flégère, and the overall limit is 10 hours. Mandatory kit includes a waterproof jacket, a 1-litre water reserve and a survival blanket. The 90 km, 23 km, 10 km, a vertical kilometre and other races run alongside, and more than 10,000 runners take part across the programme. The 42 km was part of the Golden Trail World Series from 2018 to 2024.