Zegama-Aizkorri: Race Guide to Europe's Toughest Skyrace

Zegama-Aizkorri race guide: the 42 km course with 2,736 m of climbing, the lottery entry timeline, kit for Basque mud, and a 16 week training outline.

Zegama-Aizkorri is a marathon in the way that a knife fight is a conversation. The distance is 42 km. The elevation is 2,736 m of climbing. It runs on a loop out of a Basque village of fewer than 1,500 people, through mud, cloud, and beech forest, past four of the highest peaks in the Aizkorri massif, watched by crowds that press so tightly on the Sancti Spiritu climb that the runners disappear into them. It has been the sport's most atmospheric one-day race for two decades, and it opens the Golden Trail World Series. This guide covers the course, the entry lottery, and how to prepare for gradients that make a road marathon look like a warm-up.

The course

A 42 km loop starting and finishing in Zegama, in the Gipuzkoa province of the Basque Country, northern Spain, with 2,736 m of positive elevation (iRunFar, 2026).

The shape of the day:

Kilometres 0 to 16, the long climb. Almost entirely uphill from the village to Aratz, part of the Aizkorri massif. The gradient is relentless rather than brutal, and the mistake is running it because you feel good.

Kilometre 20, Sancti Spiritu. A 600 m climb up a steep wall, lined the whole way by spectators packed shoulder to shoulder. It is the most photographed section in trail running and the noise is genuinely disorienting.

The ridgeline. The route takes in Aratz, Aizkorri, Aitxuri, and Andraitz, the high points of the massif, on ground that is exposed to whatever the Atlantic sends.

The descent to Zegama. Long, steep, and frequently greasy. This is where the race is decided for everyone outside the front twenty.

Why it is genuinely hard

The gradient profile is the answer. Averaging 65 m of climbing per kilometre across a marathon distance means very little of the course is runnable at anything resembling a road pace.

Add the weather. The Basque Country in May delivers fog, rain, and mud with high reliability, and the limestone underfoot becomes slick when wet. Cold conditions and deep mud have marked several recent editions.

As the opening event of the Golden Trail World Series, the front of the field is as deep as any race in the sport (Golden Trail World Series, 2026). Winning times sit around 3 hours 50 minutes to 4 hours 20 minutes depending on conditions. Mid-pack runners take 6 to 8 hours. A road marathoner with a 3:15 personal best should expect to take twice that here.

Getting a place at Zegama-Aizkorri

Demand vastly exceeds the small field, and entry runs through a public lottery.

  • Pre-registration opens in mid-January and runs for roughly ten days, through the race's registration platform
  • 225 places are allocated by lottery
  • The draw is public, held at the City Hall in Zegama in February, and it is streamed (Zegama-Aizkorri, 2026)
  • Additional places go to runners with qualifying times, to residents of the town, and to those who have completed every edition

The elite field is invited, and as the opening race of the Golden Trail World Series it attracts most of the sport's best mountain runners.

Practical advice: put the mid-January window in your calendar the previous autumn. Missing it costs you a year, and the timeline is tighter than most major races.

Preparing for 2,736 m in a marathon

Zegama rewards a specific profile: strong sustained climbing, confident technical descending, and the ability to run hard for five to eight hours rather than move steadily for twenty.

Vertical is the priority. Target 1,500 to 2,500 m of climbing per week during the specific phase, with at least one session that accumulates 1,200 m or more in a single effort. Our vertical gain training guide covers how to build it if you do not live near mountains.

Descending is the differentiator. The final descent is long and slippery, and quadriceps that have not been trained eccentrically will fail on it. Include dedicated downhill sessions from twelve weeks out.

Threshold matters more than in an ultra. Unlike a 100 miler, Zegama is run at a genuinely hard intensity. Include sustained climbing intervals: 4 to 6 repetitions of 8 minutes uphill at threshold effort, with jog-back recovery.

A 16 week outline:

  • Weeks 1 to 5: base, weekly vertical toward 1,200 m, long runs to 3 hours
  • Weeks 6 to 11: specific, weekly vertical 1,500 to 2,500 m, uphill threshold work, deliberate technical descending
  • Weeks 12 to 14: peak, longest runs 4 to 5 hours with 1,800 m plus, in wet conditions where possible
  • Weeks 15 to 16: taper

Run the Race Predictor against the profile before setting a goal time, because road-derived estimates are meaningless at this gradient. The Race Readiness check will tell you whether your vertical is tracking where it needs to be.

Kit and conditions

Zegama's mandatory kit list is shorter than an alpine ultra's but the conditions justify what is on it.

  • Shoes: deep, aggressive lugs. This is not a course for a moderate-tread all-rounder. Mud is the default assumption
  • Waterproof jacket: required, and you will likely need it
  • Poles: permitted and used by many mid-pack runners, though the front of the field often runs without them
  • Layers: the summits can be 10 C colder than the village with wind on top
  • Fueling: 60 to 90 g of carbohydrate per hour, and at this intensity liquids and gels outperform solids. Our real food versus gels guide covers the choice

Logistics

  • Getting there: San Sebastián is around 50 minutes by road, Bilbao around 70 minutes. Both have airports
  • Accommodation: Zegama itself has very little. Most runners stay in Beasain, Ordizia, Vitoria-Gasteiz, or San Sebastián
  • Timing: the race is held in May, and the surrounding weekend has a festival atmosphere throughout the valley
  • Language: Basque and Spanish. English information is available but limited
  • Spectating: if you do not get a place, going to watch is genuinely one of the best experiences in the sport

Official information is published at zegama-aizkorri.com.

Key takeaways

  • 42 km with 2,736 m of climbing, averaging 65 m of ascent per kilometre
  • Entry is by public lottery with 225 places, pre-registration in mid-January and the draw in February
  • The Sancti Spiritu climb at kilometre 20 is the sport's most famous section of spectator noise
  • Mud and fog are the default expectation, so aggressive lugs are essential
  • Mid-pack finishing times of 6 to 8 hours are normal, roughly double an equivalent road marathon

Where to go from here

If Zegama is on your list, the entry timeline is the thing to act on first, since the January window is easy to miss. Then build the climbing and descending specificity across a winter, because this course punishes flat fitness more obviously than almost any race at the distance.

Trailia builds plans around actual elevation profiles, so a 42 km race with 2,736 m of climbing gets trained as the mountain event it is rather than as a marathon.

Citations

  • iRunFar (2026). 2026 Zegama-Aizkorri Marathon Preview.
  • Zegama-Aizkorri (2026). Official race information, enrolment and pre-registration lists.
  • Golden Trail World Series (2026). Zegama-Aizkorri race profile.
  • UTMB World (2026). Zegama-Aizkorri Mendi Maratoia, 50K index race listing.

Frequently Asked Questions

How hard is Zegama-Aizkorri?

It packs 2,736 metres of climbing into 42 kilometres, averaging 65 metres of ascent per kilometre, which leaves very little of the course runnable at road pace. Mid-pack finishers take 6 to 8 hours, roughly double an equivalent road marathon time. Mud, fog, and slick limestone make it harder still in most years.

How do you get into Zegama-Aizkorri?

Entry is by public lottery with 225 places available. Pre-registration opens in mid-January and runs for around ten days, with the draw held publicly at Zegama City Hall in February. Additional places go to runners with qualifying times, town residents, and those who have completed every edition.

What is the Sancti Spiritu climb?

A 600 metre steep climb at around kilometre 20, lined the entire way by spectators packed shoulder to shoulder. It is the most photographed section in trail running and the noise is genuinely disorienting for first-timers. Runners describe effectively disappearing into the crowd as they climb.

What shoes should I wear at Zegama?

Deep, aggressive lugs. Mud is the default assumption in the Basque Country in May, and the limestone underfoot becomes slick when wet. A moderate-tread all-rounder is the wrong tool here, particularly on the long final descent.

How should I train for Zegama-Aizkorri?

Prioritise vertical, targeting 1,500 to 2,500 metres of climbing per week during the specific phase with at least one session accumulating 1,200 metres in a single effort. Add uphill threshold intervals, since this race is run at genuinely hard intensity unlike a 100 miler. Dedicated downhill sessions from twelve weeks out protect your quadriceps for the final descent.

What are the winning times at Zegama?

Front runners typically finish between 3 hours 50 minutes and 4 hours 20 minutes depending on conditions. As the opening race of the Golden Trail World Series, Zegama attracts most of the sport's best mountain runners each year. Mid-pack times of 6 to 8 hours are entirely normal.

Where should I stay for Zegama-Aizkorri?

Zegama itself has very little accommodation, so most runners stay in Beasain, Ordizia, Vitoria-Gasteiz, or San Sebastián. San Sebastián is around 50 minutes by road and Bilbao around 70 minutes, and both have airports. Book early, since the whole valley fills up for race weekend.

Should I use poles at Zegama?

Poles are permitted and many mid-pack runners use them, particularly on the long opening climb and Sancti Spiritu. The front of the field often runs without them. If you plan to use poles, train with them well before race day so your upper body is conditioned for the load.

How much should I eat and drink during Zegama?

Target 60 to 90 grams of carbohydrate per hour, and at this intensity liquids and gels clear the stomach better than solid food. The high effort level reduces gut blood flow, so anything heavy is likely to sit undigested. Practise your intake on hard uphill sessions rather than easy long runs.

Is Zegama worth watching if I cannot get a place?

Genuinely yes, and many runners make the trip specifically to spectate. The Sancti Spiritu climb offers the best atmosphere in the sport, and the surrounding weekend has a festival feel throughout the valley. It also gives you a realistic sense of the terrain before you enter.

Tools for this race