The marathon is a long-distance foot race with a distance of 42.195 km (26 mi 385 yd), usually run as a road race, but the distance can be covered on trail routes. The marathon can be completed by running or with a run/walk strategy. There are also wheelchair divisions. More than 800 marathons are held throughout the world each year, with the vast majority of competitors being recreational athletes, as larger marathons can have tens of thousands of participants.

The marathon was one of the original modern Olympic events in 1896. The distance did not become standardized until 1921. The distance is also included in the World Athletics Championships, which began in 1983. It is the only running road race included in both championship competitions (walking races on the roads are also contested in both).