Trail des Châtaignes is an autumn trail-running weekend in Val-d'Oise, north-west of Paris, based at Fort de Cormeilles-en-Parisis. It starts from the fort above the Buttes du Parisis and offers five events across the weekend rather than a single race. Saturday is built around dog-friendly formats, with a canicross and a canirando organized with the Canipirates club, followed by a 22 km night trail. Sunday brings the main trail options: Les Châtaignes over 36 km and Le Fort over 17 km.
The routes were planned with local heritage managers so the event can use the massif while leaving sensitive sections to recover. The field includes regular trail runners, people chasing a tougher weekend challenge, and participants running or walking with their dogs. Anyone wanting extra mileage can pair the Saturday night race with either Sunday distance and get a separate combined-event ranking. The 17 km race is treated as the second classic of the Châtaignes program, while another short option is billed locally as small but tough. Places are limited, and photographers such as Suitic Photographies and Xavier Samson cover the weekend.