Course Highlights — 90km du Mont-Blanc 2026 Kilometre by Kilometre
Seven sections, one night and one day of racing. The 90km du Mont-Blanc is run in two radically different states: the first 40 km in darkness through the Aiguilles Rouges and Switzerland, the next 50 in full daylight across the balconies of Chamonix and high alpine terrain. Here is how to approach each segment.
The Night Start and the Climb to the Brévent (km 0 – 15)
4:45am, Place du Triangle de l’Amitié, Chamonix. The June chill of the high alpine valley, hundreds of headtorches blazing, stars overhead in the Mont-Blanc massif — one of the most striking starts on the ultra-trail calendar. The route immediately climbs from the town toward Planpraz and then the Brévent (2,525 m), the first major high point. This night climb of over 1,500 m D+ is the opening test of the 90km: technical, exposed, with cliff-edge passages on terrain that can be icy at this hour. Runners who fly up the Brévent with energy to spare have usually misjudged their start. The golden rule for this section: target heart rate, poles out, eyes on the trail rather than the lights of Chamonix below. A misstep at 4am at 2,000 m can compromise 84 km of racing.
Across the Aiguilles Rouges and into Switzerland — Lac d’Émosson (km 15 – 40)
After the Brévent, the route traces the western ridges of the Aiguilles Rouges Nature Reserve in wild, unspoilt alpine terrain. The climb to the Lac d’Émosson (1,930 m, Switzerland) is the centrepiece of this section — a reservoir lake suspended in a high mountain cirque, with views across the glaciers and the Mont-Blanc massif. Crossing into Switzerland means two practical points that must not be overlooked: your mobile phone needs a plan that works on the Swiss network, and your personal accident insurance must cover search and rescue costs in Switzerland. Over these 25 km, daylight arrives progressively. Drink regularly even without feeling thirsty.
Col des Posettes and the Return to France (km 40 – 55)
From Émosson, the route climbs toward the Col des Posettes (1,997 m), the border crossing back into France. The ascent is sustained and technical, the terrain rocky and exposed. The descent from the col to Vallorcine (1,260 m) is one of the longest negative descent sections on the course: nearly 1,000 m of D- over 5.5 km, starting rocky and technical at the top before giving way to a single-track through forest. On quadriceps that have already climbed the Brévent and Émosson, this descent will hurt badly if you take it without care. Ultra-short stride, knees bent, no rushing. Vallorcine is the first full valley aid station after Switzerland: reload completely here.
Col des Montets and the Flégère (km 55 – 70)
From Vallorcine, the route heads to the hamlet of Buet, then follows the Chemin des Diligences to the Col des Montets (1,461 m), at the heart of the Aiguilles Rouges Nature Reserve. Now with the Mont-Blanc chain exposed to the east, the trail climbs toward the Flégère (1,875 m), a panoramic balcony with direct views over the Argentière glacier and the massif’s great north faces. The traverse across the balcony to the Combe de la Charlanon is one of the most spectacular passages on the course: a narrow trail along a grass cliff with the Chamonix plain 800 m below. Maximum concentration required on this section.
Montenvers and the Mer de Glace (km 70 – 75)
Montenvers (1,913 m) hosts the km 75 aid station, with a cut-off time set at last wave start time + 19h45. It is the most iconic moment of the finale: from the Montenvers terrace, the Mer de Glace — France’s largest glacier at 7 km long — stretches out below. Arriving at this point after 70+ km of racing, in the full morning light, with this staggering view, is a moment that finishers consistently describe as the emotional turning point of the race. If you pass Montenvers within the cut-off, you have every chance of finishing.
Plan de l’Aiguille — The Last Mountain (km 75 – 81)
From Montenvers, the route takes on the final major climb: the Plan de l’Aiguille refuge (2,310 m), at km 81 with a cut-off of start time + 21h45. At 75 km of racing with 5,400 m D+ already in the legs, this ascent is as much a test of character as physical fitness. Plan de l’Aiguille is the last high point before the final descent: panoramic views across the entire chain, the Vallée Blanche and, on a clear day, the summit of Mont-Blanc itself. It is also, for many runners, where cramps hit. Electrolytes, controlled climbing stride, poles — everything counts here.
The Final Descent to Chamonix (km 81 – 88)
From Plan de l’Aiguille, the descent to Chamonix: 7 km over 1,300 m of D-, on technical trails alternating scree, forest and exposed passages. The urge to accelerate and “come home” is strong, but exhausted quadriceps on a steep technical descent is a guaranteed recipe for a fall or a cramp. Treat these 7 km with the same focus as Plan de l’Aiguille: short stride, deliberate footfall, progressive acceleration over the final 2 km as the trail eases. The finish at the Place du Triangle de l’Amitié, in the mid-morning Chamonix sunshine with Mont-Blanc as a backdrop, is an image that stays with finishers for life.
Course Summary — Kilometre by Kilometre
| Section |
Key locations |
Profile and terrain |
| 0 – 15 km |
Chamonix (1,035 m, 4:45am), Planpraz, Brévent (2,525 m) — full darkness |
Steep climb +1,500 m D+, night, exposed |
| 15 – 40 km |
Aiguilles Rouges, Buet, Lac d’Émosson (1,930 m, Switzerland) — sunrise |
Ridges, international crossing, high alpine |
| 40 – 55 km |
Col des Posettes (1,997 m) back to France, Vallorcine (1,260 m) — aid station |
Technical descent 1,000 m D-, valley floor |
| 55 – 70 km |
Buet, Chemin des Diligences, Col des Montets, Flégère (1,875 m), Combe Charlanon |
Panoramic balcony, narrow trail, exposed passages |
| 70 – 75 km |
Montenvers (1,913 m), Mer de Glace — aid station km 75 (cut-off +19h45) |
Glacier view, emotional turning point |
| 75 – 81 km |
Plan de l’Aiguille (2,310 m) — aid station km 81 (cut-off +21h45) |
Final climb, alpine terrain, Mont-Blanc view |
| 81 – 88 km |
Final descent to Chamonix — Place du Triangle de l’Amitié |
1,300 m D- descent, scree then forest |
Elevation Profile
With 6,200 m of elevation gain across 88 km, the 90km du Mont-Blanc is the most demanding race in this article cluster by D+/km (70 m/km). The profile is not a single dome: it includes six distinct climbs (Brévent, Émosson, Col des Posettes, Flégère, Montenvers, Plan de l’Aiguille), each preceded or followed by a technical descent. Maximum altitude is around 2,525 m (Brévent), reached in darkness around the second hour of racing. The course frequently sits above 2,000 m altitude, with residual snow sections virtually guaranteed in June. The final descent from Plan de l’Aiguille (2,310 m) to Chamonix (1,035 m) packs 1,300 m D- into 7 km.
Key warnings for the 90km du Mont-Blanc 2026: four elements that must be anticipated. First: snow. The regulations explicitly state that “some sections of the course take place exclusively in snow.” In June at 2,000–2,500 m in the Mont-Blanc massif, snow sections are virtually certain, particularly on the ridges between Émosson and the Col des Posettes. Second: Swiss insurance. The course crosses into Switzerland. Your personal accident insurance must cover search and rescue costs in Switzerland as well as France. Third: mobile phone coverage. Your phone needs a data plan that works on both French and Swiss networks. Fourth: the Montenvers cut-off. Runners who arrive at km 75 just inside the cut-off with spent legs have very little chance of reaching Plan de l’Aiguille (km 81) in time. Assess your condition at Montenvers, not just your clock time.
Race Strategy for the 90km du Mont-Blanc 2026
The 90km du Mont-Blanc demands a clear section-by-section strategy. No target pace across the board — each climb is managed by heart rate, each descent by foot placement technique.
The Night Climb to the Brévent: Patience and Thermal Management
Two traps to avoid on the Brévent climb (km 0–15): going out too fast in the excitement of the 4:45am start, and underestimating the cold. In June at 2,500 m at 6am, temperatures can drop below 0°C with wind. Wear a warm layer for the first third of the climb and remove it afterwards. On the night ascent, if your headtorch lights up more than 10 metres ahead of you, you are going too fast for the terrain.
Switzerland and the Return to France: Fuel Up and Respect the Vallorcine Descent
The Swiss section (km 15–55) is the longest on the course. Over the 25 km between Émosson and Vallorcine, aid stations are spaced far apart: eat from your pack regularly, drink at every opportunity. The descent to Vallorcine demands maximum conservatism. Treat the Vallorcine aid station as a mini base camp: refill water and food, check your feet if needed.
Montenvers and Plan de l’Aiguille: Manage the Cut-Offs as Targets, Not Threats
At Montenvers (km 75): if you arrive with more than an hour of margin over the cut-off, you can finish. Less than an hour: mobilise every remaining resource for the climb to Plan de l’Aiguille. At Plan de l’Aiguille (km 81): if you pass within the cut-off, the final descent to Chamonix is achievable even at reduced pace. Walk any gradients above 15% without ego on this final section.
Practical Information
Bib Collection — Mandatory Kit Check
The 90km bib collection takes place on Thursday 25 June 2026, 9am–9pm, at the EMC2 space, Place du Mont-Blanc, Chamonix. Runners must present:
- Photo ID
- Race pack with all mandatory kit for on-site inspection
- The timing chip is fitted at bib collection (not on race day)
- No bib will be issued without complete kit or photo ID
- No bibs will be distributed on the night of Thursday/Friday before the race
Mandatory Kit (main list)
- Waterproof jacket with hood (gore-tex type), properly fitted
- Water supply: 1 litre minimum
- Charged mobile phone with coverage in France AND Switzerland
- Photo ID (required throughout the race)
- Survival blanket, whistle, headtorch + spare batteries
- Personal accident insurance covering search and rescue in France AND Switzerland
- Full list on marathonmontblanc.fr
Getting There — Eco Travel
- By train (40% of entries reserved for train/bus arrivals): from Geneva (~1h by TER), Lyon (~3h via Annecy), Paris (~5h30 by TGV + TER). Chamonix-Mont-Blanc station is 10 min walk from the Place du Triangle de l’Amitié
- By bus: regular services from Geneva Airport (1h15)
- By car: A40 from Lyon or Geneva, exit Chamonix
Weekend Schedule
- Thursday 25 June: Trail Camp, Expo, 90km bib collection (9am–9pm) with mandatory kit check
- Friday 26 June: 90km start at 4:45am, first finishers from 2:30pm
- Saturday 27 June: KM Vertical start 4pm, 90km prize giving at 3:05pm
- Sunday 28 June: 23km start 8am, 42km start (elite women 6:45am / general 7:15am)
FAQ — 90km du Mont-Blanc 2026
Why is it called “90km” when the official distance is 88 km?
The “90km” name is historical and commercial. The actual measured distance is 88 km according to official measurements (WeRun, ITRA). Since GPS systems and different measurement tools can give varying results, the organisation maintains the “90km” designation which has become the race’s identity.
Where does the 90km du Mont-Blanc 2026 start?
The race starts on Friday 26 June 2026 at 4:45am at the Place du Triangle de l’Amitié in Chamonix. This is also the finish (loop course). Chamonix-Mont-Blanc train station is a 10-minute walk away.
What is the minimum level required to enter?
The organisation states that a runner with an UTMB Index below 450 points has very little chance of finishing the race. The 90km requires solid high-mountain experience, confidence on technical terrain and the ability to be self-sufficient for many hours. Entry is via ballot draw.
Is there really snow on the course in June?
Yes. The organisation confirms this explicitly in its regulations: “some sections of the course take place exclusively in snow.” In June at 2,000–2,500 m in the Mont-Blanc massif, snow-covered sections are virtually certain, particularly on the ridges between Émosson and the Col des Posettes. A backup course (78 km / 5,000 m D+) is in place for extreme weather conditions.
What are the intermediate cut-off times?
Two official intermediate cut-offs: Montenvers (km 75): last wave start time + 19h45. Plan de l’Aiguille (km 81): last wave start time + 21h45. The overall time limit at Chamonix is 24 hours per wave.
What is the 2026 finisher gift?
For 2026, the finisher gift is a personalised nutrition plan developed by Baptiste Ellmenreich (Chamonix elite athlete), adapted to the race’s official aid station food and to your level or estimated finish time. No physical gift this year.
Which towns and locations does the 90km course pass through?
The course passes through Chamonix (start/finish), climbs to the Brévent, follows the Aiguilles Rouges, crosses into Switzerland at the Lac d’Émosson, descends via the Col des Posettes to Vallorcine and the hamlet of Buet, crosses the Col des Montets, climbs to the Flégère, traverses the balconies to Montenvers (Mer de Glace), climbs to Plan de l’Aiguille and descends to Chamonix.
Celebrate Your 90km du Mont-Blanc 2026 with The Post Trace
88 km in a loop through the Mont-Blanc massif, a night on the Brévent, the Mer de Glace at sunrise, snow underfoot in June, and the finish at the Place du Triangle de l’Amitié in front of thousands of spectators. This is a race you run once or twice in a lifetime as a trail runner. It deserves a memory that matches it.
At The Post Trace, we turn your GPS trace into a hand-crafted map poster made in Lyon on recycled paper. Your exact loop through the massif, your race number, your finish time — an object to hang, gift or simply keep.
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