La Nuit AJT - 21 km is a semi-nocturnal urban trail race in Trévoux, located on the Saône River north of Lyon. The event takes place in September, with the Bas-Port serving as the race headquarters. The 21 km distance is the longest available for adults, offered alongside 5 km and 10 km races, a children's race, and a walking option, making the evening suitable for both runners and local families.
AJT Saône Vallée organizes the race. Its format is distinctive for the area, featuring a city trail run that extends into the evening, differing from typical daytime road races. The 21 km course is classified as trail running, yet its urban environment sets it apart from mountain or forest trails. La Nuit AJT also forms part of the Challenge Saône 4 Seasons, comprising four races, providing local, regular runners with an additional incentive to participate.