Japan's largest and most prestigious ultramarathon returns on the weekend of 24-25 April 2026, as the Mt. Fuji 100 takes its place on an increasingly deep spring ultra calendar. The race covers 166.6km with 7,038m of cumulative ascent on a route that circumnavigates the country's most recognisable mountain, stitching together forest tracks, mountain trails and local footpaths through Yamanashi and Shizuoka prefectures. It is a race that rewards patience and precise pacing as much as raw climbing ability.
The 2026 edition continues the race's steady ascent of trail running's international hierarchy. Since taking its place as a founding member of the World Trail Majors series in 2024, the event formerly known as Ultra-Trail Mt. Fuji has drawn a deeper international elite field and more demanding coverage commitments. The weekend programme retains three distances — the flagship FUJI 100 mile, the KAI 70k with 3,052m of climb, and the ASUMI 40k — meaning both first-time Japanese mountain racers and experienced 100-mile veterans are catered for on the same course network.
Organisers have retained the race's signature midnight start for the 100-mile distance, meaning runners tackle the first ascents by headtorch before dawn breaks over Fuji's eastern flanks. It is a feature that divides opinion but one that makes the race distinctive: the opening hours are run in cool forest air, and the first proper glimpse of the volcano comes only after runners have already covered significant ground. With a 44.5-hour cut-off, the full length of the course is designed to be completed by all but the most ambitious finishers before the sun sets on Saturday evening.
The course itself is more technical than its relatively modest climbing profile suggests. Sections of the circumnavigation drop on to loose volcanic scree, while the forest singletrack in the Tanzawa and Fuji-Hakone areas is knotted with roots and slick stones when wet. Spring weather around the mountain is notoriously changeable, and organisers have routinely re-routed sections in recent years to avoid residual snow or unstable ground. Runners preparing for the event are advised to arrive with a wet-weather kit list that can cope with conditions ranging from single-digit temperatures on the passes to humid warmth in the lowland farmland sections.
Beyond the racing, Mt. Fuji 100 has become a significant cultural moment for Japanese trail running, drawing crowds to aid stations in towns such as Fujikawaguchiko and Oshino Hakkai that are already global tourist destinations. With international travel now a more settled part of the sport's calendar, the 2026 edition is expected to draw one of the largest overseas contingents since the race's rebrand. Expect a race defined by the weather Fuji decides to serve up as much as by any individual athlete — the volcano has a habit of imposing its own rhythm on a field no matter how well prepared they arrive.