15 Hardest Ultra Marathons in the World

Ultra marathons are the ultimate test of athletes’ physical and mental grit. Achieving the seemingly impossible is the ultimate high. No matter how grueling or exhausting these races are, athletes travel around the world to experience them in all their terrifying glory.

But what sets the hardest ultras in the world apart from the rest?

The distance is not the greatest challenge in the world’s hardest ultra marathons. Athletes are up against intense, technical terrain, extreme weather conditions, long, steep ascents, high altitude, minimal support along the way, demanding cutoff times, navigating the route, and mental fatigue. 

The following 15 races should be on every ultra runner’s bucket list. They are some of the most infamous, difficult ultra marathons in the world – perfect for runners who are not afraid of a serious challenge! 

What Are The Hardest Ultra Marathons in the World?

The World's Hardest Ultra Marathons

The Barkley Marathons

Let’s start by saying that only 15 runners have finished the Barkley Marathons since 1986. Not one participant finished in 2021. This ultra marathon in rural East Tennessee is supposed to verge on the impossible.

The race is disorganized by design. Athletes have no idea of the exact distance, the starting time, or even the route. The unknown adds an extra element of difficulty.

Runners are woken in the middle of the night by the sound of a conch shell being blown. This signals the start of the race. 

Now for the race itself: it consists of five loops (runner’s call them the five loops of death). Each loop is somewhere between 20 and 26 miles, and runners have to complete them all in under 60 hours.

Don’t picture a neatly manicured trail when you imagine the Barkley Marathons. Athletes must clear the trails as they go, battling dense patches of briar. 

Running the Barkley Marathons is the equivalent of summitting Mount Everest from sea level (a fitness trend known as Everesting), TWICE! The race has an elevation gain of 60 000 feet. 

For all of the above reasons, this race is undisputedly at the top of our list. 

See more: Why is the Barkley Marathons so hard?

Western States 100

The Western States 100 in the US is the oldest 100-mile race in the world! This endurance run takes place in Squaw Valley, California, and runners from all over the world come to conquer it. 

Runners have just 30 hours to cover 100.2 miles of remote, rugged terrain. Most of the route is only accessible on foot or by helicopter. 

The Western States 100 follows the original trail that silver and gold miners took in the 1850’s. It goes through deep canyons, icy rivers, and over snowy mountains. 

The temperature along the route can vary from 20°F to more than 110°F. In this race, runners battle against the elements. 

Athletes must contend with 18 000 feet of elevation gain and an even greater descent of 23 000 feet. In the first 4 miles of this race, runners ascend over 2500 feet! 


The Spartathlon race
The Spartathlon race, image courtesy of the official website

This legendary race in Greece starts in Athens and ends in Sparta. In just 36 hours, athletes must cover 152.8 miles. No wonder only roughly 40% of entrants finish. 

The Spartathlon is steeped in history. It follows the route that the ancient Athenian long-distance runner, Pheidippides, had to run in 490 BC. 

Before the battle of Marathon in the war between the Greeks and the Persians, Pheidippides had to run from Athens to Sparta to get his army help. He ran this distance in a single day!

To commemorate his feat, the Spartathlon ultra marathon was started in 1984. Runners must contend with the distance, a vertical climb of almost 4000 feet, and the scorching heat of the Mediterranean summer. 

See more: Our complete Spartathlon race guide

Montane Yukon Arctic Ultra

The Arctic Ultra has a reputation of being the toughest, coldest ultra marathon in the world. It follows the same track as the Yukon Quest Trail – the world’s hardest sled dog race. 

It starts in Canada’s Yukon Territory. Runners make their way through the extreme cold (9°F to 30°F), biting winds, and a vertical climb of almost 20 000 feet. The race ends along the banks of the Arctic Circle in a tiny village called Tuktoyaktuk. 

Besides the physical challenge, runners have to face the dangers of frostbite and hypothermia and the mental battle against exhaustion. One mistake could literally cost your life. 

The record holder for the 430-mile race is Casper Wakefield from Denmark. They completed the distance in 186 hours and 50 minutes – almost 8 days! 

See more: Our guide to the Montane Yukon Arctic Ultra

La Ultra – The High

This high-altitude ultra marathon in the Indian Himalayas promises to be the adventure (and challenge) of a lifetime. Ladakh is a magical region of the world, and runners get to experience the beauty and cruelty of this frozen desert environment.

Athletes must cover a distance of 345 miles in under 120 hours. As if the distance and the cutoff time aren’t enough, runners also have to contend with the lack of oxygen and altitude sickness. The entire race has an average altitude of 14 500 feet above sea level. 

The race starts in Nubra Valley, and athletes must climb 5 massive peaks, all of which are over 17 000 feet above sea level. The weather conditions are extreme, with temperatures ranging from 104°F all the way down to 14°F.

If you can look past the mental and physical fatigue, you will see some of the most breathtaking vistas in the world. This race is truly one for the bucket list (there are many shorter versions of this race to begin with!).

The Moab 240 

How does a full circumnavigation of Utah’s Moab Desert sound? Crazy, right? Now picture doing it in under 113 hours. 

This is what athletes doing the Moab 240 are in for. The 240-mile route runs through the arduous desert terrain of Arches National Park. 

Athletes must surmount two mountain ranges: Shay Mountain and the La Sal Mountain ranges, making a total vertical ascent of 29 467 feet! Did we mention the cutoff time is 113 hours?!

The Moab 240 is extremely demanding, both physically and mentally. Many participants are known to suffer hallucinations from sleep deprivation and exhaustion. 

The temperatures in the Moab range from 7°F to 95°F, so runners have to be prepared for scorching heat during the day and icy nights. Athletes have to focus all the time to navigate the steep cliffs, exposed mountains, and steer clear of the snakes, spiders, and scorpions along the way! 

Finishing the Moab 240 is truly an achievement of a lifetime. 

Badwater 135

Death Valley, California, is home to the Badwater 135 – an extreme ultra marathon that takes experienced runners from the lowest elevation in the US (Badwater Basin) all the way to of the highest mountain in the US, Mount Whitney.

The route covers 135 miles, has a total vertical climb of 14 600 feet, and runners must finish it in just 48 hours. 

Yoshihiko Ishikawa, a 31-year old man from Japan, holds the record for the fastest time – just 21 hours and 33 minutes! The fastest woman, Patrycja Bereznowska from Poland, finished it in 24 hours 13 minutes.

The Jungle Marathon

This race is described as “the world’s most terrifying adventure”. The Jungle Marathon takes place in Manu National Park, Peru, in the Amazon Rainforest. 

Runners have to make it from the Andes Mountains to the Madre de Dios River – a journey of 143 miles. Over six days, runners must conquer the difficult jungle terrain in high heat and even higher humidity.

The route takes athletes through some of the most majestic environments in the world – jungle, rainforest, and cloud forest. Athletes must traverse swamps and cross rivers. 

This beautiful but harsh landscape is home to jaguars, howler monkeys, tarantulas, snakes, mosquitos, biting ants, and scorpions – a lot to steer clear of. 

The Jungle Marathon is not only a test of physical and mental endurance, but athletes’ survival skills and knowledge of the wild are tested. 

Hardrock 100

The Hardrock 100 takes place in the stunning Rocky Mountains of southern Colorado. Runners are challenged to some of the hardest, steepest trails in the Rockies. In Hardrock 100, remoteness, steepness, and altitude is the name of the game. 

This endurance run honors the hard-as-rock miners who built many of the trails on which the race is run in the 1850s. It runs along exposed cliffs, boulder fields, snowpacks, and scree slopes.

This event is a test of runners physical and mental endurance, as well as their navigation and mountaineering skills. 

Athletes doing the Hardrock 100 must conquer the 100.5-mile course at an average elevation of 11 000 feet in just 48 hours. They must make a vertical ascent of almost 33 000 feet, as well as a descent of 33 000 feet! That is an elevation change of almost 66 000 feet!

The run is a loop that starts and ends in Silverton, Colorado. The highest point in the race is the summit of Handies Peak – 14 048 feet above sea level. 

On average, it takes runners 40 hours and 23 minutes to complete this challenge. In 2021, Francois D’Haene ran it in 21 hours and 45 minutes, setting the record for the fastest time ever. Diana Finkel holds the women’s record – she completed it in 27 hours and 18 minutes. 

Marathon des Sables

The Marathon des Sables or ‘Marathon of Sands’ is a grueling seven day, 155-mile journey through the scorching Sahara Desert in Morocco.

This ultra marathon was started in 1986 after the founder, Patrick Bauer, trekked 217 miles through this desert with only the food and water in his backpack to survive. Today it is one of the world’s most popular ultra marathons. 

Athletes have to contend with the blistering heat (temperatures reach over 122°F), both of the air and the desert sand, and they have to carry everything they need for the seven days on their backs.

The Marathon de Sables is a completely self-supported event. Imagine running over 150 miles in the desert carrying a third of your body weight on your back! 

The run is done in six stages, with one day of rest after the longest stage. 

The Ultra-Trail du Mont-Blanc

This is the running version of the 106-mile Tour du Mont Blanc hiking trail in the Alps. While most hikers take about 9 days to finish the trail, athletes doing the Ultra-Trail du Mont-Blanc are expected to finish in only 46.5 hours (just shy of 2 days).

UTMB course
The legendary UTMB course

The trail takes athletes through 3 different countries. It begins in Chamonix, France, goes through Italy to Switzerland, and back to France. 

The Ultra-Trail du Mont-Blanc features magnificent scenery, but it comes at a price! Athletes must climb steep mountains, some 3000 feet high, and make a total vertical ascent of 32,900 feet. Runners also have to contend with unpredictable weather conditions.

In 2021 Francois De’Haene (record holder for the Hardrock 100) completed it in 20 hours and 45 minutes – the fastest time that the route has ever been run. 

Hurt 100

This 100-mile endurance run on the island of Oahu, Hawaii, gets its name for two reasons: it is the Hawaiian Ultra Running Team’s trail, and it will make you hurt.

Athletes have 36 hours to complete the 100-mile course. It consists of 5 laps through beautiful rainforest, along steep ridgelines, and along sheer embankments. Runners have to make 20 river crossings as well as contend with the difficult terrain.

Part of what makes this race hurt so much is the 24 500 feet of elevation gain, as well as the 24 500-foot descent. 

In 2013, Gary Robbins set the record time for the Hurt 100, completing it in just 19 hours and 35 minutes. The record-holding woman is Tracy Garneau. She finished in 24 hours and 6 minutes. 

Berghaus Dragon’s Back Race

The Berghaus Dragon’s Back Race is a race that is completely trackless and trail-less! This is the ultimate test of runners’ navigational skills.

Set in Wales, runners have to make the 196-mile journey from Conwy Castle to Cardiff Castle. It is done in stages over 6 days and the cutoff times are brutal.

Participants run along the ‘spine’ of Wales, which is where the name Dragon’s Back comes from. 

SkyRun 100

The SkyRun 100
The stunning scenery on the SKyRun 100, image courtesy of official website

The SkyRun 100 in the Drakensberg Mountains in South Africa is another one on the bucket lists of the world’s top ultra runners. 

This 62-mile ultra marathon may be on the short side distance-wise, but it has a total vertical ascent of over 14 500 feet, and runners must complete the course in under 30 hours.

The SkyRun is a high-altitude race (6500-8200 feet above sea level) along the skyline of the Maluti Mountains, between South Africa and Lesotho. 

Tor de Géants

This ultra marathon takes place in Italy’s gorgeous Aosta Valley. The course traverses 25 mountain passes in the Alps.

Athletes are given 150 hours to complete the 205-mile race. There is a total vertical ascent of over 78,000 feet.

The record-holding man for the Tor de Géants is Franco Colle, with a time of 64 hours and 43 minutes. The fastest woman to finish the race was Silvia Ainhoa Trigueros Garrote, who too 85 hours and 23 minutes. 

Think you can handle these crazy races? Head on over to our ultramarathon training guide to see if you have what it takes!

See more: the 5 best books about ultra running!

Author Profile

Michael Paulson

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Michael is a frequent contributor, which is a miracle to us as he quite literally runs for days with the rest of his time. An ultra marathon specialist, Mike is the kind of guy who posts a 30K Morning Run on Strava before we’ve had our breakfast and prefixes it with the smart-assery: “Guess I wasn’t feeling it today.” He runs like he writes: slow with bits flying everywhere.
Michael Paulson

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