Nestled in the heart of the French Alps, the Mont Blanc Marathon is one of the most prestigious trail running events in the world. Held annually in Chamonix, the race offers participants the opportunity to challenge themselves on some of the most breathtaking and technical mountain trails in Europe. With a range of distances, from the grueling 90 km ultra to the beginner-friendly 10 km, this event caters to runners of all skill levels, providing a world-class racing experience amidst stunning alpine scenery.
This comprehensive guide covers everything you need to know about the Mont Blanc Marathon, including detailed race overviews, terrain insights, training tips, nutrition strategies, and mental preparation techniques to ensure you’re fully equipped for race day.
A Legacy of Mountain Running Excellence
The Mont Blanc Marathon has become a premier event in the international trail running calendar, attracting elite and amateur runners alike. Chamonix, often regarded as the birthplace of alpinism, serves as the perfect backdrop for this race, with its dramatic peaks, high-altitude trails, and steep elevation gains.
The event spans three days, offering multiple races that showcase the diverse landscapes of the Mont Blanc Massif. Runners will experience forested trails, open alpine meadows, rocky ridgelines, and panoramic viewpoints, making it one of the most scenic and challenging races in the world.
Race Categories: Choose Your Challenge
1. 90 km du Mont-Blanc – The Ultimate Alpine Ultra
The 90 km race is the toughest event of the weekend, designed for seasoned ultra-trail runners who are ready to take on an extreme challenge.
Distance: 90 km (56 miles)
Elevation Gain: 6,220 meters (20,400 feet)
Start Time: Friday, June 27, 2025, at 4:00 AM
Course Overview:
Starting in Chamonix, runners embark on a punishing course featuring relentless climbs, technical ridgelines, and steep descents. The trail weaves through high-altitude alpine terrain, with sections reaching over 2,500 meters (8,200 feet). The course is a mix of rocky, single-track trails, snow-covered paths, and breathtaking ridges, making it as technically demanding as it is beautiful.
This race tests endurance, resilience, and strategic pacing, requiring runners to manage their energy over an ultra-distance course with extreme elevation gain. The cutoff time is 24 hours, making it a race that only the toughest competitors will complete.
2. 42 km du Mont-Blanc – A Marathon Like No Other
The Mont Blanc Marathon is one of the most iconic trail marathons in the world, offering stunning scenery, challenging ascents, and technical terrain.
Distance: 42 km (26.2 miles)
Elevation Gain: 2,540 meters (8,330 feet)
Start Time: Sunday, June 29, 2025
Course Overview:
This marathon is nothing like a traditional road race. Runners will ascend over 2,500 meters, tackling steep climbs and exhilarating downhills while navigating rocky trails, alpine pastures, and dense forests. The final descent into Chamonix is one of the most thrilling sections of the course, offering stunning views of Mont Blanc and the Aiguilles Rouges.
The challenging elevation profile requires strong hill climbing ability, technical downhill skills, and endurance to sustain effort over rugged terrain.
3. 23 km du Mont-Blanc – A Shorter Yet Intense Challenge
Distance: 23 km (14.3 miles)
Elevation Gain: 1,680 meters (5,510 feet)
Start Time: Saturday, June 28, 2025
Course Overview:
First held in 1979, this race is one of the oldest and most respected short-distance mountain races in Europe. While shorter than the marathon, the course features substantial elevation gain and technical terrain, making it physically demanding. Runners will climb through alpine forests and rocky mountain trails, experiencing a true mountain running adventure in a condensed format.
This race is perfect for intermediate trail runners looking for a challenge that doesn’t require ultra-distance endurance but still demands technical ability and strength.
4. 10 km du Mont-Blanc – The Gateway to Trail Running
Distance: 10 km (6.2 miles)
Elevation Gain: 325 meters (1,065 feet)
Start Time: Saturday, June 28, 2025
Course Overview:
Designed for beginners and those who want a faster, less intense race, the 10 km course takes runners on a scenic loop around Chamonix, featuring rolling trails with gentle climbs. This race is ideal for first-time trail runners, offering a fun and accessible introduction to mountain running.
5. Kilomètre Vertical (Vertical KM) – A Pure Climbing Challenge
Distance: 3.8 km (2.4 miles)
Elevation Gain: 1,000 meters (3,280 feet)
Start Time: Friday, June 27, 2025
Course Overview:
The Vertical Kilometer (VK) is a brutal but exhilarating race, requiring runners to climb 1,000 meters over a short distance. The course follows an unrelenting uphill trail, finishing at Brevent, one of the most scenic viewpoints in Chamonix.
This race is a pure test of uphill endurance, leg strength, and mental toughness, making it one of the most intense short-distance challenges in trail running.
Preparing for the Mont Blanc Marathon
1. Strength and Conditioning for Mountain Running
The steep climbs and technical descents of Mont Blanc require specific strength training:
- Hill Repeats & Stair Climbing – Simulate the relentless ascents.
- Squats, Lunges & Step-Ups – Build quad, hamstring, and glute strength.
- Downhill Training – Improve control and stability for steep descents.
2. Adapting to Altitude
- Train on Hills & Trails – If you don’t live at altitude, focus on hill workouts to mimic the race effort.
- Breathing Techniques – Practice deep breathing to improve oxygen efficiency.
- Hydration & Electrolytes – Dehydration happens faster at altitude, so stay hydrated and replace lost electrolytes.
3. Race-Day Nutrition and Hydration
- Eat Every 45 Minutes – Consume 200-300 calories per hour for sustained energy.
- Hydration Plan – Drink 500-750ml per hour, adjusting for effort and temperature.
- Electrolyte Balance – Use salt capsules or electrolyte drinks to avoid cramps.
4. Mental Preparation
- Break the Race into Sections – Focus on one climb or checkpoint at a time.
- Embrace Discomfort – Expect fatigue, but train yourself to keep pushing forward.
- Visualize Success – Picture yourself crossing the finish line to stay motivated.
The Mont Blanc Marathon is one of the most beautiful, prestigious, and challenging trail running events in the world. Whether you’re tackling the brutal 90 km ultra, the iconic 42 km marathon, or testing yourself on the Vertical KM, this race will push your limits and reward you with unforgettable mountain views and a sense of incredible accomplishment.
With the right training, nutrition, and mindset, you’ll be ready to take on the trails of Mont Blanc and experience one of the greatest trail running adventures of your life.
Good luck, and see you on the trails of Chamonix!
