Trail running is an exciting and often challenging pastime that has gained popularity steadily over the last decade. As more runners and hikers have taken up this outdoor activity, we’ve also seen a growing number of trail running races and ultramarathons popping up around the world.
Some of these races are exceptionally difficult, with hazards and challenges like dizzying ascents, freezing temperatures, high altitudes, extreme heat, long distances, and even obstacle courses. Whether you’re looking for a lofty new goal or just some inspiration for your training, here are some of the toughest trail running races the world has to offer.
6633 Arctic Ultra
Location: Yukon Territory and Northwest Territories, Canada
Distance: 380 miles and 120 miles (612 km and 193 km)
Toughest Parts: extreme cold, distance
With frigid temperatures and a serious risk of frostbite and hypothermia, the 6633 Arctic Ultra is not for the faint of heart. The race is held in February in Canada’s Yukon and Northwest Territories. As a result, competitors must deal with icy winds, snow, and temperatures well below freezing.
There are two versions of the race: a 120-mile (193-km) and a 380-mile (612-km) route. Runners must complete the shorter version within three days, while those on the longer route have nine days to complete their journey. The 380-mile race ends in Tuktoyaktuk at the edge of the Arctic Circle, making it a unique and exciting finish line.
The incredibly remote location offers gorgeous scenery and shows few signs of human life. Athletes in the 6633 Arctic Ultra primarily race without support or assistance. Competitors must carry all their own gear, with many using a sled towed behind them as they run.
Location: Death Valley, California, USA
Distance: 135 miles / 217 km
Elevation Gain: 14,600 ft / 4,450 m
Toughest Parts: heat, elevation gain
The Badwater 135 covers 135 miles (217 km) through the hottest, driest, and lowest place in North America: Death Valley National Park in California. Runners have 48 hours to get from Death Valley’s Badwater Basin to Whitney Portal. The finish line is the trailhead to the summit of Mt. Whitney, the tallest mountain in the lower 48 states. The grueling race packs in 14,600 feet (4,450 meters) of elevation gain and takes runners through three different mountain ranges. Runners in this ultra should prepare for extreme temperatures – the invitation-only race typically takes place in July in one of the hottest places on Earth.
Location: Wartburg, Tennessee, USA
Distance: 100 miles (161 km)
Elevation Gain: 60,000 feet (18,288 m)
Toughest Parts: navigation, elevation gain
Held in Wartburg, Tennessee’s Frozen Head State Park, the Barkley Marathons is one of the most notorious and toughest trail running races in history. It’s so challenging, in fact, that fewer than 20 people have ever finished, and over half of the races have had no finishers.
The race consists of five loops that create an unmarked 100+ mile (161+ km) course. Runners must complete the course in 60 hours. The Barkley Marathons was inspired by James Earl Ray, a prisoner who assassinated Martin Luther King, Jr. and later escaped Brushy Mountain State Penitentiary in 1977. Although he only made it about 8 miles through the backcountry, his escape led Gary “Lazarus Lake” Cantrell to launch the Barkley Marathons in 1986.
The Barkley Marathons race is held in March or April and is capped at 40 participants. As there is no official website, the application and selection process for the fabled Barkley Marathons remains a well-kept secret in the running world.
Location: Wales, UK
Distance: 200 miles / 320 km
Elevation Gain: 50,000 ft / 15,240 m
Toughest Parts: technical terrain, navigation
Typically held in September, this arduous trail race takes participants through picturesque mountain scenery and past ancient castles in Wales. The five-day Dragon’s Back Race packs in around 50,000 feet (15,240 meters) of elevation gain over about 200 miles (320 km). In order to compete each day, participants must arrive at mandatory checkpoints and reach camp by specific cutoff times.
The terrain is technical, with rock scrambles, steep slopes, loose scree, and river crossings. Since the trail is unmarked, navigation skills are critical for success. Only around half of participants reach the finish line in a given year.
Location: Everest Base Camp, Nepal
Distance: 26.2 miles / 42 km
Elevation Loss: 6,694 feet / 2,040 m of descent
Toughest Parts: altitude, cold temperatures
While not as long as many of the competitions on this list, the Everest Marathon earns a place as one of the world’s toughest trail running races due to the high altitude and extreme weather. Known as the highest marathon on the planet, the race begins at the Everest Expedition Base Camp, located around 18,000 feet (5,486 m) above sea level. Runners then descend over the course of 26.2 miles (42 km) to the finish line at Namche Bazaar (11,306 feet / 3,446 m). The race is typically held in May, and temperatures can be frigid.
Runners must arrive in Nepal three weeks before the race to give their bodies time to acclimate to the altitude. In addition to visiting Kathmandu, runners will experience a 14-day trek to the starting point at Everest Base Camp, turning this race into an exciting three-week adventure.
Location: La Réunion Island
Distance: 100 miles / 161 km
Elevation Gain: 31,820 ft / 9,700 m
Toughest Parts: humidity, dense jungle vegetation, steep terrain
Located in the Indian Ocean off the coast of Madagascar, the island of Réunion hosts a demanding trail race called The Grand Raid. The run takes participants through the island’s diverse and difficult landscapes, including dense jungle, steep rock faces, sandy deserts, active volcanoes, and lava fields.
The race is so brutal that it has been dubbed ‘The Madmen’s Diagonal.’ Over 100 miles (161 km), runners will climb up and down mountains for a total elevation gain of 31,820 ft (9,700 m). You’ll need to be sure-footed and have good rock climbing skills to tackle The Grand Raid, which is usually held in October.
Location: Hong Kong
Distance: 185 miles / 298 km
Elevation Gain: 47,572 ft / 14,500 m
Toughest Parts: elevation gain, distance, steep terrain
Each year, Hong Kong hosts a punishing three-day race called the Hong Kong Four Trails Ultra Challenge (HK4TUC). The course is one of the toughest trail running races in the world and requires competitors to cover 185 miles (298 kilometers) on Hong Kong’s four major trails. These include the MacLehose Trail (62 miles /100 km), the Wilson Trail (48 miles / 78 km), the Hong Kong Trail (31 miles / 50 km), and the Lantau Trail (43 miles / 70 km).
The difficulty becomes clear when you look at the race’s staggering statistics. The HK4TUC distance is equivalent to running seven marathons back to back, and the elevation gain is almost twice the height of Mt. Everest. If you run the HK4TUC, it’s like climbing to the top of Mt. Everest from Base Camp over three times! Moreover, it’s self-supported, so you won’t find any aid stations or checkpoints along the trail.
Participants who finish within 60 hours or less are considered “finishers,” while those who complete the race in 72 hours or less earn the title “survivors.” The Challenge does not recognize any runners who finish after the 72-hour mark. The by-invite-only race is held annually during Chinese New Year.
Location: Silverton, Colorado, USA
Distance: 100 miles / 161 km
Elevation Gain: 33,000 ft / 10,000 m
Toughest Parts: elevation gain, altitude, extreme weather
The Hardrock 100 is an endurance run that follows dirt trails for 100 miles (161 km) through the San Juan Mountains in Colorado’s Rocky Mountains. The run begins and ends in Silverton, Colorado. Runners have 48 hours to complete the marked trail, which passes through the resort towns of Telluride and Ouray and mining ghost towns like Sherman.
Due to the remote location and steep terrain, skills like wilderness survival, navigation, and mountaineering are just as essential as endurance. With an average elevation of more than 11,000 feet (3,352 m) above sea level, altitude is also a big factor in the difficulty of this race. The highest point along the course is the 14,048-foot (4,282-m) summit of Handies Peak, so participants must be acclimated to higher altitudes to succeed in the Hardrock 100.
Location: Amazonia, Brazil
Distance: 124 miles / 200 km
Elevation Gain: n/a
Toughest Parts: heat, humidity, dangerous wildlife, dense jungle
The Jungle Marathon in Amazonia, Brazil, is considered among the most dangerous and toughest trail running races on the globe. The extreme race takes place within the protected Tapajos National Forest, part of the Amazon rainforest. Over the course of six days, participants test their endurance as they race through the Brazilian jungle, with almost no support or resources (some checkpoints do offer water).
Runners must face scorching temperatures up to 113°F ( 45°C), nearly 100% humidity, river and swamp crossings, and threatening wildlife like jaguars, snakes, caimans, and scorpions. However, some of the biggest threats are heat-related illnesses and electrolyte imbalances. Due to the difficulty and extreme environment, few competitors can complete the Jungle Marathon successfully.
Location: Ladakh, India
Distance: 207 miles / 333 km
Elevation Gain: 18,000 ft / 5,490 m
Toughest Parts: altitude, extreme temperatures, elevation gain
Also called The High, La Ultra 333 is a 207-mile (333-km) endurance race through the Himalayas in India. In just 72 hours, competitors must navigate three 16,404-foot (5,000-meter) mountain passes and varying terrain in India’s high-altitude desert and Himalayan mountains. The environment is marked by massive temperature swings, with temperatures rising from below freezing to 104°F (40°C) in just a few hours.
If that sounds too extreme, several shorter versions of the race range from 7 miles to 69 miles (11 km to 111 km). The organizers also added an even more challenging version covering a whopping 345 miles (555 km) in 2019, but they don’t appear to be repeating it in 2022. Because of the dangers of altitude sickness, participants are required to undergo a mandatory acclimatization period before the race, regardless of the distance they choose to run.
Location: Madeira, Portugal
Distance: 71 miles / 115 km
Elevation Gain: 23,000 feet / 7,000 m
Toughest Parts: technical and steep terrain, elevation gain
The Portuguese island of Madeira is often referred to as the Hawaii of Europe, thanks to its lush green mountains rising from the Atlantic Ocean. In April, the island hosts the Madeira Island Ultra Trail (MIUT), a difficult 71-mile (115-km) race that spans the length of the entire island. The route features incredible views of Madeira’s peaks and valleys, streams, waterfalls, and unique wildlife. Competitors will also summit the island’s highest peaks, including Pico Ruivo and Areeiro.
While the distance is not as long as some of the other races on our list, the difficulty should not be underestimated. The route has many steep ascents and descents that require good footing and careful technique. There are shorter versions ranging from 10 to 53 miles (16 km to 85 km) for those who are newer to racing.
Location: Sahara Desert, Morocco
Distance: 155 miles / 250 km
Elevation Gain: varies
Toughest Parts: distance, heat
Over the course of seven days, participants in the Marathon des Sables must run 155 miles (250 km) through the Moroccan Sahara. The ultramarathon usually occurs between March and May, and the course changes each year.
The Marathon des Sables is one of the world’s toughest trail running races because of the distance, remote desert location, scorching heat, and self-sufficiency requirements. The race is self-supported, so participants must carry their own food, water, and equipment for the duration of the week. The race is popular and almost always sells out. Since 1986, the Marathon des Sables has hosted over 22,000 competitors.
Location: Northern England
Distance: 268 miles / 431 km
Elevation Gain: 43,100 ft / 13,135 m
Toughest Parts: bad weather, distance, elevation gain
Known as one of Europe’s toughest trail running races, the Montane Spine Race traverses some of England’s most challenging and rugged terrain. This winter ultramarathon is held in January and stretches across the entire Pennine Way, one of the UK’s most iconic and difficult long-distance trails. The race is so strenuous that around three-quarters of participants are unable to finish.
The nonstop, seven-day race is particularly grueling because of the weather conditions in January. With fog, rain, snow, wind, and cold temperatures, the race tests competitors’ endurance in addition to their mental strength. The conditions are so challenging at times that the race has been described as “268 miles of pain,” and hypothermia and frostbite are very real risks.
Those who are up to the challenge will experience stunning winter scenery across northern England, like Northumberland National Park, the Peak District, and Yorkshire Dales. For those who are hesitant, there are shorter versions of the Spine race to get started, which range from 42 to 108 miles.
Location: Manitou Springs, Colorado, USA
Distance: 26.2 miles / 42 km
Elevation Gain: 7,800 feet (2,380 m)
Toughest Parts: steep terrain, altitude
Dating back to 1956, the Pikes Peak Marathon is the oldest continually held marathon in the USA. Despite the short length compared to some of the ultramarathon races, the Pikes Peak Marathon is a brutal race. Runners must make their way from the starting point in Manitou Springs at 6,300 feet (1,920 m) in elevation and make their way up to the summit of Pikes Peak at 14,115 feet (4,302 m).
The climb is around 7,800 vertical feet (2,380 m) with a steep incline – the average grade of the course is 11%. Adding to the challenge is the narrow, winding trail, which zig-zags up the mountain. Runners will encounter sharp turns and varied surfaces, including gravel, dirt, and rocks. Many people who have completed the race say the steep descent is even more harrowing.
To qualify for the Pikes Peak Marathon, competitors must have completed a marathon or longer race in less than six hours within the last three years. The race is usually held in September, and there is sometimes snow at the summit. As a result, runners must prepare for varying weather conditions and temperatures.
Location: Aosta Valley, Italy
Distance: 205 miles / 330 km
Elevation Gain: 78,740 ft / 24,000 m
Toughest Parts: extreme weather, elevation gain, distance
Translated as ‘Tour of the Giants,’ Tor des Geants takes stamina and mental fortitude to complete. The TDG covers 205 miles (330 km) in the Italian Alps and has a staggering 78,740 ft (24,000 m) of ascent. Runners also have to deal with high altitudes and navigate 25 mountain passes over 6,650 ft (2,000 m).
One of the most challenging aspects of this race is the weather. Italy’s alpine regions often experience extreme and unpleasant weather conditions during the race in September, including thunderstorms, hail, lightning, freezing temperatures, sleet, snow, and rain.
The TDG is one of the longest nonstop trail races globally, and only around 50% of competitors finish. There are no checkpoints or stages – the only timing rule is that you must cross the finish line within 150 hours.
Distance: 31 miles / 50 km
Elevation Gain: varies
Toughest Parts: physically demanding obstacles
The Spartan Race merges trail running with obstacle course racing, adding a new and challenging element for competitors. The races are held in locations around the world and vary in length and difficulty, with the Spartan Ultra being the most demanding.
Spartan Ultra competitors must run 31 miles (50 km) and conquer 60 different obstacles, such as log carries, cargo nets, rope climbs, and sandbag carries. The race is a great fit for experienced trail runners seeking an added challenge and anyone who wants to test their physical and mental limits. The Spartan team provides training tips for your first race. You can also choose to warm up with one of their shorter races, such as the Spartan Sprint, Super, or Beast, before trying the Ultra.
Location: Germany, Austria, Italy
Distance: 162 miles / 260 km
Elevation Gain: 49,200 feet / 15,000 m
Toughest Parts: exposure, elevation
The Transalpine Run crosses the Alps in eight stages over the course of 162 miles (260 km). Competitors begin the trek in Garmisch-Partenkirchen, Bavaria, Germany, pass through parts of Austria, and end at Brixen in South Tyrol, Italy. The race features some of the Alps’ most beautiful scenery, including high mountain passes, forests, and meadows.
Unlike many races on this list, the Transalpine Run has competitors run in pairs. It is also well-supported, with bags and gear transferred to the next location. Still, the Transalpine Run is tough due to the 49,200 feet (15,000 m) of ascent and challenging terrain. With snow-covered mountains and slippery scree slopes, the race poses a risk of falling, so you’ll want to be sure-footed if you attempt this race. Because of the potential dangers, competitors must remain within 20 seconds of their teammate at all times.
Location: France, Italy, Switzerland
Distance: 106 miles / 170 km
Elevation Gain: 32,800 feet / 10,000 m
Toughest Parts: elevation gain, elite competition
The Ultra-Trail du Mont Blanc (UTMB) is an iconic and stunningly beautiful trail race that wraps around Mont Blanc. Over 106 miles (170 km), runners will ascend around 32,800 feet (10,000 m) and experience some of the most picturesque scenery in the Alps. The race is held in late August or early September, attracts elite runners, and sees around 2,500 participants each year.
Runners begin in Chamonix and have 46.5 hours to complete the loop trail, which travels through France, Italy, and Switzerland. The elevation gain is harsh and makes this race a challenge, but the mountain vistas dotted with charming alpine villages make the UTMB a very rewarding pursuit.
Location: Olympic Valley to Auburn, California, USA
Distance: 100 miles / 161 km
Elevation Gain: 18,000 feet / 5,486 m
Toughest Parts: heat, competition from elite runners
Held in June in California’s Sierra Valley, the Western States 100 is the world’s oldest 100-mile race. The ultra run is infamous for its scalding temperatures in the California summer. The most difficult part of the race for numerous runners is a 30-mile stretch called the Canyons, which features a series of strenuous ascents and descents. Many runners reach this portion at midday when temperatures are highest, making the terrain feel especially punishing. Western States is also one of the most prestigious ultra races in the US, so expect an added challenge from elite competition.
There are usually around 400 competitors in the race, and you need to complete a qualifying race to enter. Runners have a 30-hour cut-off to finish the WSER, and those that finish in less than 24 hours receive a silver belt buckle for their achievement.
Running any of these races is an enormous feat that requires dedication, endurance, mental toughness, and years of training. Despite the challenges, dangers, and long preparation, running in a demanding trail race is an experience like no other. If you’re new to trail running and aspire to compete in some of these races, check out our post about How to Get Started with Trail Running for some general advice and training tips. If you’ve been trail running for a while and are ready to sign up for your race, we wish you the best of luck!