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Most people will never attempt to run a marathon, and “enjoyable” isn’t the word even the most seasoned runners would use to describe what it’s like to run 26.2 miles in one go. However, there are some particularly brave souls who view that as a walk in the park compared to the ultramarathons that serve as the ultimate test of fitness and endurance.
These are the longest and most demanding ultramarathons on the planet
I feel like most people are aware that the marathon can be traced back to a Greek messenger who purportedly ran to Athens to deliver the news of a victory at the Battle of Marathon before promptly dropping dead.
That likely apocryphal story could be viewed as a cautionary tale about the dangers of running long distances as quickly as possible. However, it served as the inspiration for the first-ever marathon when Athens hosted the modern Olympics in 1896.
That race required runners to traverse a route that spanned 25 miles (the distance from Marathon to Athens), and 26.2 eventually became the standard after the course at the London Olympics in 1908 was extended so the royal family could see the finish line from their box at White City Stadium.
Long-distance running was A Thing before the marathon was introduced, but it ushered in a new era where being able to say you’ve run 26.2 miles has become a point of pride for many people. There are also many others who have decided that isn’t enough, which led to the rise of the so-called “ultramarathons” that task you with covering even greater distances.
There is no shortage of challenges to pick from on that particular front, but there are some particularly daunting ones that really stand out. I’m ranking these based on distance, but there are certain factors that have the potential to make comparatively shorter ones even more challenging than some of their longer counterparts.
Barkley Marathons
The Barkley Marathons is the shortest ultra on this list, but that is not a reflection of how hard it is.
The event is overseen by Gary “Lazarus Lake” Cantrell, who has earned a reputation as a bit of a mad genius since he organized the inaugural running in 1986. The course is constantly changing due to Cantrell’s efforts to make it as challenging as possible, but runners are given 60 hours to complete five 20-mile laps that require them to conquer the steep elevation at Tennessee’s Frozen Head State Park.
Entering is much easier said than done. There’s no open registration, and if you’re able to track down the email address where you send an application, you’ll have to answer a nonsensical questionnaire, submit it at a particular time, and pay a $1.60 fee on top of whatever piece of clothing Cantrell requests (if you’re running it for the first time, you’ll have to bring a license plate from your state, and if you’ve completed it before, you have to bring him a pack of Camel cigarettes).
Hundreds of people have competed since the race’s inception, but only 20 have managed to complete it.
Badwater 135
Simply visiting Death Valley in the middle of the summer is a questionable decision, but there are some people who not only do that but opt to run a 135-mile race that begins in one of the hottest places on the planet.
The Badwater 135 kicks off there each July, and runners are forced to deal with the crippling heat and more than 20,000 feet of altitude change with the help of the 8,300 ft. ascent to the trailhead of Mount Whitney, which serves as the finish line.
There’s a 48-hour time limit, although Yoshihiko Ishikawa made comparatively quick work of the course when he finished in 21 hours, 33 minutes, and a single second to set a record in 2019.
The Jungle Ultra
Your typical marathon features a well-defined course designed with runners in mind. However, the Jungle Ultra is not a typical marathon by any means.
The distance and course vary year to year, but one thing is for certain: you’ll be trekking through the Amazon rainforest while dealing with thick undergrowth, raging rivers, suffocating humidity, and any dangerous animals you may encounter along the way.
The Tunnel
You might not be able to properly appreciate the scenery you’ll be able to take in during the vast majority of the ultramarathons on this list, but you at least have the opportunity to absorb your surroundings.
However, that is not really the case with The Tunnel, a 200-mile race that consists of 100 “out-n-back” laps through the Combe Down railway tunnel in Bath, England. There is some dim lighting available during the day, but you’ll be thrust into complete darkness between 11 PM and 5 AM.
In 2025, Alex Marshall set a new record with a time of 41 hours, 16 minutes, and 43 seconds while becoming the first woman to win the race outright.
La Ultra—The High
It’s one thing to climb a single mountain in the Himalayas with the aid of experienced guides and the equipment that you typically need to weather the elements and lack of oxygen you’ll have to grapple with.
However, that has nothing on La Ultra—The High, a 333-kilometer (207-mile) race through the mountains in India’s Ladakh region. Competitors have to scale three different mountain passes that rise over 17,500 feet above sea level while dealing with the lack of oxygen and frigid conditions that contribute to the difficulty.
Dragon’s Back Race
Wales is home to a mountain range known as the Brecon Beacons, which is a stretch that’s home to its tallest peak (the 2,907-foot Pen y Fan) and is said to resemble a dragon’s back due to the jagged nature of the terrain.
The people who compete in the Dragon’s Back Race get up close and personal with the mountains that are used to train Britain’s military and special forces during a 380 km (236-mile) journey where heavy fog can obscure your vision as you deal with a cumulative ascent that clocks in at close to 54,000 feet.
Max King is currently the man to beat thanks to the time of 45 hours, 39 minutes, and 18 seconds he posted in 2024.
Moab 240
Utah boasts some stunning natural landscapes, and you’ll have the chance to experience some of what the state has to offer if you opt to participate in the Moab 240.
However, you might not be able to fully appreciate it when you consider you’ll be tasked with completing a 240-mile loop through two national parks (Canyonlands and Arches) while dealing with more than 31,000 feet of altitude change during your travels.
Competitors are required to finish in less than 117 hours, although Michael McKnight didn’t have to worry about that time limit when he set a record of 55 hours, 49 minutes, and 58 seconds in 2021.
The Moab is also the culmination of the Triple Crown of ultramarathons clocking in at 200 miles or more. It also includes the Tahoe 200 (which boasts an elevation gain of 36,857 feet) and the Bigfoot 200 (a gain of more than 45,000 feet on the course in Washington State); in 2025, Kilian Korth set a new record for the cumulative Triple Crown time at 156 hours, 30 minutes, and 20 seconds.
Last Man Standing Ultramarathon
The Last Man Standing ultra is basically the equivalent of Stephen King’s The Long Walk. It’s held along a 4.2-mile loop in Texas, which you must complete in an hour in order to earn the right to do it all over again.
The cycle continues until, well, there’s one last man standing; in 2025, the race came to an end after Kendall Picado Fallas and Kim Gottwald both decided to call it quits following 56 laps where they ran a total of 235.2 miles.
The Spine
The Dragon’s Back isn’t the only ultra where participants have to scale some mountains in the United Kingdom, as The Spine gives them the chance to do that while traveling from England to Scotland via the 268-mile Pennine Way.
There are summer and winter versions of The Spine, with the latter viewed as the more challenging due to the weather conditions that can throw a serious hitch in your trek. In 2024, Jack Scott shattered the standing record by 10 hours with a time of 72 hours and 55 minutes while getting less than an hour of sleep during his triumph.
Yukon Arctic Ultra
Prior to 2025, the Yukon Arctic Ultra already had a reputation for being one of the toughest ultramarathons in existence, as participants could choose from a traditional marathon along with 160-kilometer and 480-kilometer options that required them to weather subzero conditions (sometimes lower than -50°F) while trekking across Canada’s most northwestern province.
Mathieu Blanchard became the first man to conquer the 600-kilometer (~372-mile) distance when it was introduced in 2025, as he (and the equipment sled he was hauling) arrived in Faro seven days and 77 hours after leaving Teslin.
6633 Arctic Ultra
The Yukon Arctic Ultra isn’t the only ultramarathon that gives you the chance to get a taste of Canada’s most inhospitable regions.
The 6633 Arctic Ultra presents similar challenges on the 380-mile course that also starts in the Yukon (specifically Eagle Plains) before racers make their way up to the Arctic Circle to finish in Tuktoyaktuk, a village in the Northwest Territories.
The record is held by Natalie Taylor and Tom Hunt, who teamed up in 2023 and crossed the finish line together after 149 hours and 47 minutes.
Iditarod Invitational
Most people associate the word “Iditarod” with the race where dog sled teams in Alaska make their way from Anchorage to Nome at the start of March each year—a 938-mile trek that usually takes around eight or nine days to complete.
However, you can also make the journey on foot thank to the Iditarod Invitational, which was held for the first time in 2000 and spans a full 1,000 miles. Participants also have the option to use skis or a bike, and most of them will opt for the courses that span 100 or 350 miles.
However, dozens of people have tried to run all 1,000—none of whom have done it quicker than Tim Hewitt, who set a record by completing it in 19 days, nine hours, and 38 minutes in 2016.
Self-Transcendence 3,100 Mile Race
Most marathons follow a course that takes you from Point A to Point B as opposed to relying on the laps that define more traditional track events. However, that is not the case with what is recognized as the longest ultramarathon on the planet.
As you can likely surmise from the name, the Self-Transcendence 3,100 Mile Race requires you to travel a distance of 3,100 miles, but the “course” in New York City is limited to a loop around four blocks that surround a high school and playground in Jamaica, Queens.
The race was “only” 2,700 miles when it was run for the first time in 1996, but it was extended to the current number the following year. Participants have 52 days to complete the 5,649 laps needed to hit the total, which requires runners to average a little more than 59 miles per day.
Ashprihanal Aalto of Finland holds the record, as he completed the requisite circuits in 40 days, nine hours, six minutes, and 21 seconds in 2015.