Défi Trails Lillois is a trail-running series in Lille, in the Nord department of Hauts-de-France. The program is built around forest races in March, with distances from 8 km up to 45 km, plus a timed event called Les 6h Lilloises.
Runners can choose 8 km, 12 km, 15 km, 22 km, 30 km, or 45 km, and each listed distance uses a single-loop format. The 12 km and 22 km races include night running, while the longer 45 km option is marked as the most popular race on the program.