Yr Wyddfa Sea to Summit
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Yr Wyddfa Sea to Summit - Mountain Ultramarathon
Yr Wyddfa Sea to Summit is a one-day, mass participation mountain ultramarathon held on 26 September 2026. The route covers approximately 29 miles (47 km) with about +5600 ft of ascent, starting at Caernarfon Castle and finishing at Bron y Feds Uchaf, Rhyd Ddu (LL54 7YS). The event is listed under Run/Trek discipline and forms part of the UK Sea to Summit trilogy of sea-to-summit ultramarathons.
The course is fully waymarked with bright orange arrows and fully supported by event staff. Professional medical cover is provided by an established event medic service with paramedics, doctors, self-contained vehicles and a private ambulance. Pit Stops provide water, hot drinks, salty snacks, sweets and fruit, plus toilets and medical help; participants should not rely solely on Pit Stops for nutrition and those with severe allergies are advised to carry their own food.
Cut-offs along the course are set to a 3mph completion pace. Key pit stop distances are published and, if runners miss the second pit stop cut-off, there is a shorter summit route option that reduces the total distance to about 20.5 miles with 5175 ft of ascent. The route uses quieter southern approaches to the mountain, passing towards Beddgelert and ascending via the Watkins Path and South Ridge, with descent via the Ranger Path.
Participants must be over 18 on the day of registration and a mandatory kit list is provided. Completing all three Sea to Summit events awards a special Trilogy medal. Visit the organization's website for the most recent information.
