The Ridgeway Challenge 86 Miles is a fully supported continuous running event that starts at Ivinghoe Beacon near Tring and ends at Avebury Stone Circle. The route is 86 miles along The Ridgeway National Trail, a 5000 year old trackway through the Chiltern Hills and North Wessex Downs (along Grim’s Ditch for several miles), Barbury Castle and Liddington Castle (hill forts) en route, way marked throughout with 1929m (6328 feet) ascent 1991m (6532 feet) descent. The event hosts the UK Ultra Distance Trail Running Championships.

The event is organised by and permitted by the Trail Running Association. Held under UK Athletics Rules of Competition.