An ultramarathon, also called ultra distance or ultra running, is a footrace longer than the traditional marathon length of 42.195 kilometres. Various distances, surfaces, and formats are raced competitively, from the shortest common ultramarathon of 31 miles (50 km) and up to 3100 miles. World Championships are held by the International Association of Ultrarunners (IAU) for 50 km, 100 km, 24 hours, and ultra trail running. The Global Organization of Multi-Day Ultramarathoners (GOMU) holds World Championships for 48 hours and 6 days. World Records are ratified and recognized by World Athletics, the IAU, and by GOMU.

Marathon des Sables, or MdS, is a seven-day, about 250 km (160 mi) ultramarathon, which is approximately the distance of six regular marathons. The longest single stage (2009) was 91 km (57 mi) long.