Ultramarathons are the pinnacle of endurance sports, testing the limits of human strength, stamina, and mental resolve. What makes these races truly formidable isn't just their extreme distances but also the harsh environments, treacherous terrains, and unpredictable weather conditions in which they are held.

While all ultramarathons are true challenges, some running races around the world are known in the trail running community as particularly difficult to complete. Whether running across the scorching sands of the Sahara Desert, climbing through the rugged peaks of the French Alps, or battling frigid Arctic winds, the events that typically make lists of "hardest races on the planet" truly have legendary status.

If you're looking for a race that will challenge every fiber of your being, the races listed below represent the toughest ultramarathons on Earth.

What You'll Learn in This Article:

• The hardest ultras in the world and why they are considered tough.
• The unique challenges runners face in terms of distance, terrain, and weather.
• Tips for preparing for the world's toughest ultras.
• Insight into the mental and physical endurance required for extreme ultra running.
• An overview of essential gear and training strategies for tackling these extreme races.

What Makes an Ultra Marathon Race Especially Hard?

Ultramarathons differ from traditional marathons in more than just distance. The hardest ultra races combine several elements—such as extreme length, unpredictable terrain, and unforgiving weather—that work together to create an unparalleled challenge.

Let's break down the main factors that make these races among the toughest races and events around the world.

Distance and Duration

For most people, running a marathon (26.2 miles) is a monumental achievement. But ultramarathons take distance to a whole new level, with races starting at 50 kilometers (31 miles) and going well beyond 100 miles.

These longer distances mean that runners often have to continue for hours or even days, running through the night, with minimal rest. This is especially true in races like the Tor des Geants, which spans 330 kilometers and takes participants several days to complete.

• 50K races: These serve as the "gateway" ultramarathons, taking most runners 6-10 hours to finish.
• 100-mile races: These legendary events, such as the Hardrock 100 or Badwater 135, can take between 24-48 hours to complete, depending on the terrain and conditions.
• 200-mile+ races: Events like the Moab 240 or Tor des Geants challenge runners to stay focused and moving for days, often pushing them to their mental and physical breaking points to complete the course.

Terrain and Elevation: Descents, Ascents, Technical Trail

Elevation gain and technical trails are defining features of many of the toughest ultramarathons.

While some races, such as the Marathon des Sables, focus on the difficulty of crossing vast deserts, others challenge runners to conquer towering mountains. For example, the Ultra Trail du Mont Blanc (UTMB), which takes place in the French Alps features more than 10,000 meters of elevation gain, forcing runners to traverse rocky, narrow, and steep trails.

In the toughest mountain races like the Hardrock 100 or UTMB, the climbs are relentless. Participants must prepare not only for the long distances but also for hours spent hiking or scrambling up steep slopes through mountain ranges. The downhill sections can be equally punishing, as runners navigate technical descents that are often slick with mud, ice, or loose rocks.

Some of the hardest trail running races in the world when it comes to elevation include:

• The Hardrock 100 which has more than 33,000 feet of climbing.
• UTMB which takes runners through three countries (France, Italy, and Switzerland) over the course of the race and features technical trails through high alpine passes.

Harsh Weather Conditions

For many ultramarathons, the weather is one of the most significant factors that make them so difficult.

Whether it's running under the scorching sun of the Sahara Desert or braving sub-zero temperatures in the Arctic, racers are constantly tested by extreme environmental conditions.

In races like the Badwater 135, held in the heat of Death Valley (the lowest elevation in North America), temperatures can reach over 130°F, while in the 6633 Arctic Ultra, runners battle freezing winds and temperatures that plummet as low as -40°F.

Candidates for the Most Challenging Ultramarathon Race in the World

When discussing the hardest ultra marathon races, a few events consistently stand out due to their difficulty. These races have earned their reputation for pushing runners to their physical and mental limits.

Marathon des Sables in the Sahara Desert

Often referred to as the "toughest foot race on Earth," the Marathon des Sables is a 250km race held over six days in the scorching Sahara Desert. Runners must contend with scorching daytime temperatures, blinding sandstorms, and the challenge of carrying all their food and supplies on their backs. The risk of dehydration is ever-present, and the vastness of the desert adds a psychological challenge, as the finish line seems endlessly far away.

• Key Challenges: Extreme heat, the need to be self-sufficient (carrying your supplies), and the mental toughness needed to face the emptiness of the desert.

Badwater 135

Held in Death Valley, the Badwater 135 race covers 135 miles. The race begins in the Badwater Basin, the lowest point in North America at 282 feet below sea level, and finishes at the base of Mount Whitney.

Runners face not only the intense heat of Death Valley but also three major climbs, totaling over 14,000 feet of elevation gain. This race is notorious for its blistering heat, with temperatures regularly exceeding 130°F, making hydration and heat management crucial.

• Key Challenges: Extreme heat, long climbs, and the mental endurance needed to survive more than 24 hours of running in one of the hottest places on Earth.

Barkley Marathons

Known for its near-zero finish rate, the Barkley Marathons event in Tennessee is one of the toughest and most notorious ultramarathons in the world. The course is unmarked, navigation is difficult, and the race distance is often longer than advertised. With a cutoff time of 60 hours, no GPS watches allowed, and no definitive route, this race is as much about mental endurance as it is about physical stamina.

• Key Challenges: Navigation, rugged terrain, and an unforgiving cutoff time. Runners often face isolation, sleep deprivation, and the psychological toll of not knowing how far they've really run.

Ultra Trail du Mont Blanc (UTMB)

The UTMB is an iconic race through the French Alps, covering 170 kilometers (about 106 miles) with more than 10,000 meters (or roughly 33,000 feet) of ascent.

What makes UTMB one of the hardest races in the world is its technical mountain terrain, which can shift rapidly from dry to snowy or icy, depending on the weather. Runners must be prepared for drastic temperature changes and high-altitude conditions as they pass through alpine passes.

• Key Challenges: Extreme elevation, technical mountain trails, and rapid weather changes.

Hardrock 100-Mile Endurance Run

The Hardrock 100 is a 100-mile race in Colorado's San Juan Mountains. Known for its brutal climbs and high-altitude running, the race demands over 33,000 feet of elevation gain, with much of it occurring at altitudes above 10,000 feet. The thin air at high altitudes makes every climb more challenging, and the rugged terrain adds an extra level of difficulty.

• Key Challenges: Altitude, extreme elevation gain, and rugged trails.

Spartathlon

The Spartathlon is a 246-kilometer race from Athens to Sparta, tracing the steps of the ancient Greek messenger Pheidippides. This race combines the challenge of long distance with strict cutoff times, forcing runners to maintain a fast pace for nearly 24 hours. The heat of the Greek sun and the unrelenting pace make it both a physical and mental battle to finish the race.

• Key Challenges: Distance, strict cutoffs, and heat.

6633 Arctic Ultra

For runners who prefer the cold, the 6633 Arctic Ultra is one of the most extreme races in the world. Covering 350 miles through the Arctic, runners face freezing temperatures, high winds, and complete isolation. The risk of frostbite and hypothermia is constant, and the mental challenge of running in such an isolated, harsh environment is immense.

• Key Challenges: Freezing temperatures, isolation, and the risk of frostbite.

Tor des Geants

The Tor des Geants is a 330-kilometer race in Italy's Aosta Valley, featuring more than 24,000 meters of ascent. This non-stop race takes place in the high mountains, where runners must navigate difficult trails, steep climbs, and extreme weather. With limited opportunities for rest, participants often go without sleep for days, making this race as much a mental test as a physical one.

• Key Challenges: Extreme elevation, non-stop format, and sleep deprivation.

Moab 240

At 240 miles, the Moab 240 is one of the longest continuous foot races in the world. Set in Utah's desert canyons and mountains, the race challenges runners to maintain their focus and endurance over several days. The dry heat, rugged terrain, and sheer distance make this race a true test of a runner's physical and mental capacity.

• Key Challenges: Distance, desert heat, and the challenge of staying focused over multiple days of running.

Montane Spine Race

The Montane Spine Race is a grueling 268-mile ultramarathon along the Pennine Way in the UK, held in January. Runners face extreme winter conditions, including freezing temperatures, snow, and relentless winds, as they navigate rugged moors and mountainous terrain with limited daylight.

• Key Challenges: Harsh winter weather, self-sufficiency, and sleep deprivation over several days of continuous running.

How to Prepare for the Toughest Ultra Marathon Races

If reading about some of the toughest races around the world inspires you to lack up your running shoes and give it a shot, there are some special considerations you should take into account when starting your training.

For more information on how to train for an ultra marathon distance race, refer to our guide titled "Training for an Ultramarathon: What Every Ultra Runner Needs to Know."

You can also get a free ultramarathon training plan designed for runners with busy lives but big goals on the MOTTIV training app.

Endurance Training and Long Runs

For all races exceeding 100 miles, endurance training is key, and long runs are the key sessions of any ultramarathon training plan. Runners must build up their stamina through long-distance runs, often spending entire weekends covering 30 to 50 miles in a single session. These long runs help prepare the body to withstand the physical strain of hours—or days—on the move.

Strength and Elevation Training

To prepare for races with significant elevation gain, such as UTMB or Hardrock 100, runners should incorporate hill training and strength workouts into their routines. Strengthening the legs, core, and upper body will help runners manage steep climbs and technical descents.

Nutrition and Hydration Strategies

Proper fueling is critical in ultra races. Without a solid nutrition plan, runners risk hitting the wall, especially in long, grueling races like Badwater 135 or Spartathlon. Hydration is equally important, particularly in desert races, where dehydration can set in quickly. Runners should practice fueling and hydration during their training runs to find the right balance for race day.

Gear for Extreme Conditions

Selecting the right gear is crucial for tackling races in extreme environments. For the Marathon des Sables, lightweight clothing and sun protection are essential, while runners in the 6633 Arctic Ultra will need insulated gear to protect against the cold. Proper footwear, hydration packs, and layers are necessary to survive these tough conditions.

Wrap-Up

Running one of the world's toughest ultramarathons is not for the faint of heart. These races demand the highest level of physical endurance, mental fortitude, and preparation. From the blistering heat of the Sahara Desert to the freezing winds of the Arctic, these events challenge runners to push their limits and redefine what they are capable of achieving.

Key Takeaways:

• Extreme distances and durations are common in the hardest ultramarathons.
• Harsh weather conditions like desert heat and Arctic cold add extra challenges.
• Technical terrain with steep climbs and descents pushes runners to their limits.
• Mental fortitude is as important as physical endurance in overcoming these races.
• Preparation with the right training, gear, and strategy is essential for success in the world's toughest ultramarathons.

If you're ready to take on one of these challenges, remember that careful preparation, training, and determination will be key to crossing the finish line.

_{Article fact checked by Ultramarathon Running Coach Cody Moore.}