Marathon Eryri

A Practical Runner’s Guide to the Course, Conditions and Fuelling for a Big Day in the Mountains

Everything You Need to Know Before Race Day

Marathon Eryri, formerly the Snowdonia Marathon, is one of the most iconic and toughest road marathons in the UK. Starting and finishing in Llanberis, it takes runners deep into the heart of Snowdonia with long climbs, dramatic scenery and a reputation for being unapologetically hard.

This is a road marathon, but not a gentle one. With over 800–900 metres of ascent, three major climbs and highly changeable mountain weather, Marathon Eryri demands respect, patience and good decision-making throughout the day.

It is a race where time goals often take a back seat to effort, resilience and experience. Many runners arrive with a target time in mind and leave with something more valuable: the satisfaction of having managed themselves well on a savage but beautiful course.

This guide is built around what runners who have completed Marathon Eryri tend to say afterwards.
What worked.
What caught them out.
What they would do differently next time.

Key Facts at a Glance

Distance is 26.2 miles
Location starts and finishes in Llanberis, Gwynedd, Wales
Terrain is primarily road with short trail and rough sections
Elevation gain is approximately 800–900 metres
Course features three major climbs
Weather is highly changeable with wind, rain and low cloud common
Field size is smaller than city marathons
Atmosphere is strong, local and deeply supportive

Marathon Eryri suits runners who enjoy a challenge and are willing to pace by effort rather than ego. The biggest challenges tend to be climbing discipline, descending fatigue, weather exposure and staying mentally steady when the course bites back.

View our Marathon Eryri Course Guide or if you’d like a deeper dive into fuelling strategies, carb targets and pacing guidance, you can read the full Mountain Fuel Road Marathon Nutrition Guide