Fell running, also sometimes known as hill running, is the sport of running and racing, off-road, over upland country where the gradient climbed is a significant component of the difficulty. The name arises from the origins of the English sport on the fells of northern Britain, especially those in the Lake District. It has elements of trail running, cross country and mountain running, but is also distinct from those disciplines.

The Wicklow Round is a long-distance hill running challenge in the Wicklow Mountains in Ireland. The route follows a prescribed 100-kilometre circuit of 26 mountains, which must be completed in a fixed order, that total over 6,000 metres (20,000 ft) of elevation; there is some flexibility on route-choices between peaks. Rounds completed outside of a cut-off time of 24-hours are not generally recorded. Irish ultra-runner Joe Lalor is credited with the creation of the Round.