An ultramarathon is any organized footrace extending beyond the standard marathon of 42.195 km. Ultra races typically begin at 50 km and can extend to enormous distances. The longest certified race is the annual Sri Chinmoy 3100 miles (4989 km) in New York.

There are three types of events - those in which one runs a set distance, those in which one attempt to cover the greatest possible distance within a fixed period of time and those in which a runner runs a certain fixed distance every day, multiday-events.

Journey running is another aspect, runners who cover long distances at their own pace. The most common examples are transcontinental runners who have crossed USA, Europe or Australia on foot. Megarunners are another sub-group. They are known not for their speed or records but for the great number of marathons and ultramarathons they run. Henri Girault, France, has run more than 500 races of 100 km or more.

The most accepted standard events are 50 km, 50 miles, 100 km, 100 miles, 6 hours, 24 hours, 48 hours, six days, 1000 km and 1000 miles. Ultramarathons are run on roads, trails and tracks. They can be point-to-point, out and back or held on loop courses.

Ultramarathon racing is much older than the marathon (which originated in 1896) but only recently has the sport has been recognized by the International Amateur Athletic Federation who in 1991 extended official recognition to the 100 km-event, now the longest running distance recognized by the world athletics governing body.