Trail Marchaux is a Halloween night trail race held in Marchaux-Chaudefontaine, located in the Doubs department of Bourgogne-Franche-Comté, near Besançon. The event takes place in late October and includes multiple participation options: 10 km and 18 km trail races, a non-timed Nordic walking event, and a 4 km lantern walk for children accompanied by adults.
The running courses feature short trail distances, not mountain-ultra lengths. The 10 km Les combottes route includes 200 m of elevation gain, with other night options named Les dolines and La chaille. The event embraces the Halloween theme, offering decorated course sections, refreshment stands, a brass band, fireworks, and the organizers' playful warning that runners "will sweat with fear."