The Isolienne Trail Challenge is a two-day mountain running event in Isola, Alpes-Maritimes, taking place in August between Isola village and the Isola 2000 ski area. Participants can choose a short Kilometre Vertical of approximately 4 km with about 970 m of elevation gain, a 35 km trail race with roughly 1,700 m of ascent, or compete in both as the KV+Trail challenge. Organized by Union Sportive d’Isola, it features a free-pace mountain format, allowing both licensed and non-licensed runners to participate and manage their own effort in semi-autonomy.
The courses are set within the Mercantour mountains, with approximately 90% of the routes on marked paths and trails, minimizing road sections. The 35 km trail race largely takes place above 2,000 m, making altitude a significant factor in the race itself. This longer route features more downhill than uphill sections, with around 2,600 m of descent. The weekend challenge incorporates a pursuit format: the Sunday trail race begins based on the rankings from Saturday's KV race, meaning the climb directly influences the start of the subsequent event. Aid stations and changing facilities are provided on site.