MB80 2026 Guide: everything about the 90 km du Mont-Blanc

What makes this race difficult is concentration. Unlike a 100-miler where the pace naturally settles into restraint, the 90 km du Mont-Blanc keeps inviting you to run, surge and attack climbs without much real downtime. Trails around Chamonix combine runnable sections, rockier traverses, steep climbs and descents where efficient hiking matters as much as running speed. Many runners underestimate the format because it sits below the symbolic 100 km line. The combination of elevation, altitude and technical stress makes it far more expensive than that simple label suggests.

The Mont Blanc massif also imposes its own rules. Even in late June, conditions can swing from heat in the valley to cold wind higher up. Light changes quickly, footing becomes less precise once fatigue builds and the final descents still demand concentration after many hours of climbing. The challenge is therefore not just to cover 88 km. It is to cover 88 km of mountain decisions while still eating, drinking and adjusting to terrain changes at the right moment.

Preparation should look like training for a high-output alpine ultra. You need a robust aerobic base, but more importantly long vertical days, back-to-back mountain weekends and specific work on damaged downhill legs. Poles are a real advantage if you already know how to use them efficiently. Fueling also needs rehearsal at moderate to moderately high intensity because this sort of race encourages late eating. Since the official 2026 course is listed at 88 km and 6,200 m of climbing, it is smarter to calibrate training around expected time on feet than around distance alone.

Logistics are standard for Chamonix, which means they become difficult when handled late. Accommodation disappears quickly across Marathon du Mont-Blanc weekend, especially within walking distance of the centre. If Chamonix is full, Les Houches, Argentière, Servoz and Sallanches are workable bases as long as transport is planned early. By rail, the valley is reachable from Paris via Bellegarde or Annecy and then onward through Saint-Gervais to Chamonix. By car, parking, traffic and bib pickup timing all need to be solved before race week.

It also helps to treat the weekend as a full project rather than a single race morning. Check bib pickup hours, start procedures, possible shuttles and mandatory kit directly on the Marathon du Mont-Blanc site. Keep the day before calm: minimal walking, simple meals, a pack prepared with weather margin and a clear post-race plan. TrailCompanion is especially useful here because it turns a busy race week into a concrete checklist, which reduces mental load before the start.

MB80 / the 90 km du Mont-Blanc rewards runners who arrive already organised. If you respect the density of the profile, prepare descents as seriously as climbs and lock Chamonix logistics early, this becomes an ambitious but entirely coherent alpine goal.