Marathon du Mont-Blanc 2026

The Marathon du Mont-Blanc is a trail-running weekend held in the Chamonix valley of Haute-Savoie, featuring eight races situated below the Mont Blanc range. Its main event is the 42 km trail marathon, taking place in late June, with 2,540 m of elevation gain and loss. This is mountain running, not a road marathon with scenery: participants require experience on uneven terrain, must carry essential equipment, and compete in semi-autonomy with only three aid stations before reaching the finish. The 42 km route begins on undulating trails before becoming more challenging on steep, technical sections. The primary difficulty lies in the ascent around the Aiguillette des Posettes, where adaptability across varied terrain is more crucial than flat-ground pace. The event is limited to 2,300 participants across six start waves, with a 10-hour time limit. Skilled trail runners compete alongside seasoned amateurs, though organizers advise that those with a UTMB performance index below 350 are unlikely to complete the race and should consider an alternative event from the weekend.