The Mont-Blanc Marathon is a trail running event in Chamonix, organised by the nonprofit Club des Sports de Chamonix, with eight races and around 10,000 runners over four days in late June. Its 42km du Mont-Blanc, which the organisers call the highlight of the weekend, is a 42 km loop from the centre of Chamonix with 2,540 m of climbing, run on the final day, limited to 2,300 runners and raced by some of the best trail runners in the sport.
Entry opens in phases each autumn. Bibs reserved for Chamonix Valley residents and for runners who commit to arriving by train or bus are sold first-come, first-served, and the other half go through a free lottery that stays open for a week. In a recent lottery, 12,800 runners applied for 1,150 places on the 42 km, about one chance in eleven. For official updates, head to the Mont-Blanc Marathon website.
Key dates
- Registration WindowExpected Oct 2027
- Race dayJun 27, 2027
Windows are shown to the month until the organiser confirms them. Subscribers get the exact day, by email, on the morning it opens.
Don't miss the opening. The Mont-Blanc Marathon is first-come, first-served and sells out. Set up a BibsAlert and we'll email you the moment registration goes live.
How to enter the Mont-Blanc Marathon
The 42km du Mont-Blanc has four ways in, all online with card payment. Every entrant pays a mandatory carbon offset based on the round trip from home to Chamonix and uploads a proof of address. Entries are personal and final: no transfers, and no refunds unless you took the optional cancellation insurance when registering.
1. Chamonix Valley Residents (First-Come, First-Served)
10% of the bibs, 230 for the 42 km, go to residents of Servoz, Les Houches, Chamonix-Mont-Blanc and Vallorcine who commit to coming by public transport, on foot or by bike, with no lottery. You upload a proof of address when you register, plus your ViaCham card if you come by train or bus. In the last round this phase opened first, a few days before the others.
2. Train/Bus Bibs (First-Come, First-Served)
40% of the bibs, 920 for the 42 km, go to runners who commit to travelling to Chamonix by train or bus, with no lottery. More than half of the journey from home and back must be by train or bus, and a round-trip ticket covering race day must be uploaded to your runner account by early May. A missing ticket or proven fraud cancels the entry without refund.
3. Lottery (Free to Enter)
The remaining 50% of the bibs, 1,150 for the 42 km, are drawn by lottery for runners using any other means of transport. Entering is free and the window stays open for a week. You can enter the draw only once, for a single race: a second entry cancels all of them. Groups of 2 to 10 runners can enter together and share one result, with the same odds as a solo entry. Results arrive by email, and selected runners then have about two weeks to complete their registration and pay.
4. Solidarity and Environmental Bibs
A limited number of solidarity and environmental bibs guarantee a place without the draw, in exchange for a donation to the Club des Sports de Chamonix, local environmental projects or partner charities. They have opened in early November.
The course
A loop from the centre of Chamonix on mountain trails between about 1,000 m and 2,200 m. The organisers describe a fast, rolling first section, then very technical trails with big climbs and descents.
- Start: Place du Triangle de l'Amitié, Chamonix
- Finish: Place du Triangle de l'Amitié, Chamonix
- Distance: 42 km (26.1 miles)
- Elevation gain: 2,540 m D+ and 2,540 m D-
- Start Time: 6:45 AM for the elite women, 7:15 AM for the elite men and wave 1, then waves 2 to 6 every ten minutes until 8:05 AM
- Time Limit: 10 hours from your wave's start. Cut-offs, counted from the last wave's start: Le Tour (km 13.5) after 2h45, Vallorcine (km 23.5) after 5h30, La Flégère (km 34.2) after 8h30
The route heads up the valley through Le Lavancher and Argentière to the Le Tour feed station, then climbs to the Aiguillette des Posettes at 2,200 m, the course's main challenge, before dropping to Vallorcine. From the Col des Montets it climbs again past Le Béchar to La Flégère, then drops past Charlanon to the finish in Chamonix, with a panoramic view of the Mont Blanc massif on the way. The race is semi-autonomous, with three full feed stations plus one at the finish, and poles are allowed if you carry them from the start. The organisers say a runner with a UTMB index below 350 has very little chance of finishing.
Why run the Mont-Blanc Marathon?
- The highlight of the weekend: the organisers' flagship race, where some of the best trail runners in the sport battle on the trails above Chamonix.
- Mont Blanc views: after the steep, technical climb to the Aiguillette des Posettes, the course finishes with a panoramic view of the Mont Blanc massif.
- A whole festival: eight races and around 10,000 runners over four days in Chamonix, with the Trail Camp expo on Place du Mont-Blanc.
Missed out?
Spots for the Mont-Blanc Marathon sell out fast. If you missed this year's window, you still have options:
- Charity & partner entries: Many races reserve guaranteed places with charity partners and official tour operators, even after general entry sells out. Check the official website for partners.
- Enter the lottery: If the first-come residents' or train/bus bibs are gone, half of the 42 km bibs are still drawn in the free lottery, open to runners using any means of transport. You can enter the draw only once, for a single race.
- Solidarity and environmental bibs: A limited number guarantee a place without the draw, in exchange for a donation to the Club des Sports de Chamonix, local environmental projects or partner charities.
- Run the 10km du Mont-Blanc: Entry has opened in early November with no lottery, first-come until all places are filled.
- Try a similar race: Check the related races below for races with similar entry types, dates, or locations.
- Be ready next year: Set up a BibsAlert so you don't miss the moment registration opens.
Questions runners ask
How do I get a bib for the 42km du Mont-Blanc?
Half the bibs are sold first-come, first-served: 40% to runners who commit to travelling to Chamonix by train or bus, and 10% to Chamonix Valley residents who come by public transport, on foot or by bike. The other half are drawn in a free lottery open to everyone, and a limited number of solidarity and environmental bibs guarantee a place in exchange for a donation.
What are my chances in the lottery?
In a recent draw, 12,800 runners entered the 42 km lottery for 1,150 places, which the organisers put at about one chance in eleven. Entering as a group of up to 10 runners gives everyone the same result but does not change the odds.
Do I need a medical certificate?
Adults need either a valid FFA Athlé Compétition, Athlé Entreprise or Athlé Running licence, or a certificate from the FFA Health Prevention Course (PPS), completed within three months of the race and uploaded to your runner account by the end of May. You also need personal accident insurance covering search and rescue costs.
Can I transfer my bib or get a refund?
No. Entries are personal and final, and transfers, exchanges and resales are banned, with a 10-year ban for anyone caught. Only runners who took the optional cancellation insurance when registering can claim a refund, from the insurer.
What mandatory kit do I need?
A working phone, at least 1 litre of water, a properly fitting hooded waterproof jacket, a survival blanket (140 x 200 cm), a cup, a whistle and cash. Bibs are only handed over after a kit check, so bring your race bag to the bib pickup.
Looking ahead
Registration for the next edition is expected between late October and early November, in several phases. Last time, first-come bibs for Chamonix Valley residents and for runners travelling by train or bus came first, then a one-week free lottery for everyone else, with solidarity bibs opening in early November. Set up a BibsAlert to get notified when registration for the 42km du Mont-Blanc opens.