Road running or road racing is the sport of running on a measured course over an established road (as opposed to track and cross country running). Such a race is called a road race. Road racing offers competitors a variety of challenges to overcome such as hills, sharp bends, varied pavement, inclement weather, and a large group to compete against- or with. Aerobic fitness, or the ability of the body to utilize oxygen, is important to have to complete the long distances. Anaerobic fitness, that is, the body's capability at responding when there isn't enough oxygen for the muscle, is necessary to charge up hills and past competitors on the finish line. A common saying for runners is that the sport is 90% mental. Recreational running became popular due to high-profile runners such as Steve Prefontaine.

Race courses are usually held on the streets of major cities and towns but could be on any sealed road. Most road races are either 5 km (3.1 miles), 10 km (6.2 miles), half-marathon (21.097 km, 13.1 miles), or marathon (42.195 km, 26.2 miles), but non-standard distances are also acceptable. The "Round the Bays" run in Auckland, New Zealand is 8.4 km (5.2 miles), the SBLI Falmouth Road Race in Falmouth Cape Cod is 7 miles long, San Francisco's "Bay to Breakers" is 12 km (7.46 miles); "City to Surf" in Sydney, Australia is 14 km, Honolulu's "Great Aloha Run" is 8.15 miles (13.12 km), and the "Charleston Distance Run " in Charleston, West Virginia is 15 miles (24.14 km). Large road races are often community-wide events that highlight or raise money for an issue or project, most notably Susan G. Komen's Race for the Cure , which is held nationwide to raise breast cancer awareness. Any running event that covers a distance further than a marathon is called an ultramarathon. These can be measured in distance (for example, 100 kilometers) or by time (whoever has run the farthest after 24 hours). Examples include the London to Brighton run in England which is just over 54 miles (87.085 km), the Comrades Marathon run between Pietermaritzburg and Durban in South Africa which is about 89 km (55.3 miles), and the Badwater Ultramarathon between Death Valley and Mount Whitney in the United States which is 135 miles (215 km).

Road running is unique among athletic events: in many cases first time amateurs are welcome to participate in the same event as current world-class champions.

Professional road racing's governing body is the IAAF. Competitors from around the world participate in what is dubbed the "elite" races for cash prizes. Kenyans and Ethiopians are renowned for their skill and it is rare for a race's top finishers not to include competitors from these countries.