Organizers of the 2025 Ultra-Trail du Mont-Blanc (UTMB) have confirmed that a series of landslides and rockfalls near Chamonix have forced a reroute of the race’s opening section, along with a slightly earlier start time.
The changes, announced just weeks before the race, aim to preserve both athlete safety and the ecological integrity of the course.
The revised UTMB course now measures 174 kilometers with 9,900 meters of elevation gain, down only marginally from the original 176K, 9,915m route that loops through France, Italy, and Switzerland.
The race will still begin in Chamonix’s Place du Triangle de l’Amitié, but the start has been moved forward by 15 minutes, to 17:45 local time on Friday, August 29.
“Recent landslides between Chamonix and Les Houches have led teams to rethink this section of the route,” read a statement from UTMB. “After several field studies, a variant was chosen to ensure your safety while preserving the spirit of the original route.”
Adjustments to the route aren’t unusual for UTMB, which regularly contends with volatile alpine weather and shifting terrain. In 2023, organizers rerouted the Col des Montets section due to poor conditions. But this year’s change is more structural, as it not only alters the course, it also affects support logistics.
One of the more notable consequences is the removal of the La Balme aid station at kilometer 40. The decision was made in collaboration with ASTERS, the Haute-Savoie Nature Conservancy, to reduce the race’s footprint on the Contamines-Montjoie Nature Reserve.
Aid stations at Les Contamines and Les Chapieux will be reinforced to make up for the loss, but runners are being asked to recalibrate their fueling and hydration strategies accordingly.
UTMB organizers have also confirmed that the TDS (Sur les Traces des Ducs de Savoie) race will see course modifications, though specifics haven’t been published.
The TDS route often cover higher, more remote terrain than the UTMB loop, and is particularly susceptible to safety concerns when weather shifts or geological instability occurs.
While logistical updates are making headlines, the race remains stacked with talent. After a DNF in 2024, Jim Walmsley returns to Chamonix hoping to reclaim the title he won in 2023.
Three-time champion Courtney Dauwalter is also back, chasing another win after skipping last year’s event. However, defending champion Katie Schide will not start, which rules out a highly anticipated rematch between the two titans of women’s ultrarunning.
Other big names expected to toe the line include New Zealand’s Ruth Croft, runner-up in 2024, as well as Canada’s Marianne Hogan, fresh off a third-place finish at this year’s Western States 100. Canadians Arden Young and Christian Meier are also slated to compete.
Though the course is slightly altered, the character of UTMB remains unchanged, a brutal, high-alpine test of endurance, grit, and race-day planning. With over 10,000 athletes descending on Chamonix for the week-long festival of races, the flagship event will once again serve as the centerpiece of the UTMB World Series Finals.
Full course maps and updated elevation profiles are available via the UTMB website.
