Over the last few years, social media has been dominated with running challenges, from back to back marathons to multi-day races and even running the length of Africa. It seems that running a marathon isn’t enough any more, as runners become hungry for greater challenges and to see just how far they can push themselves. As a result, ultras and 24-hour races have increased in popularity, all over the world.
If you’re looking for your next big challenge, then here are some of the world’s most extreme ultra running events to add to your bucket list, from technical mountain trails and snowy glaciers to self-navigated courses and the festival-like atmosphere of 24-hour challenges.
Western States 100-mile Endurance Run
100 miles
Western States 100-mile Endurance Run (WSER) is the ultimate race for most ultra runners, given it’s the world’s oldest 100 mile trail race. Won by trail running legends such as Tom Evans and Jim Walmsley, it’s recognised as one of the ultimate endurance tests in the world.
The race begins in Olympic Valley, California and ends in Auburn. Between the two locations is about 5,500m of climbing and usually in blaring sunshine, across technical yet beautiful trails.
Unlike most races, where you receive a medal at the finish, at WSER, you get a belt buckle: silver for sub 24-hours and bronze for sub 30 hours.
Badwater 135
135 miles
100 miles isn’t quite enough for some people, so instead, they do the Badwater 135, which, as the name suggests, covers 135 miles from Death Valley to Mt Whitney, in California. Traversing across three mountain ranges, with around 4450m of elevation, this is a demanding race, taking you from the lowest valleys to the highest peaks in the US.
Big Dog’s Backyard Ultra
As many 4.167 mile loops as you can do in 24 hours
The concept of running a looped course for as long as possible has endurance race designer Gary ‘Lazarus Lake’ Cantrell, the man behind the infamous Barkley Marathons, to thank. For it was Cantrell who created the very first Backyard Ultra, in Tennessee, in 2011: Big Dog’s Backyard Ultra.
This is a race unlike no other, because there is no finish. Runners must consecutively run the 6706 metre (4.167 mile) loop, in less than one hour, or they’re out. In 2023, the record was claimed by Harvey Lewis, who ran for 108 hours, covering 450 miles.
There are many similar races around the world created upon the same concept – but this is the original.
6633 Arctic Ultra
120, 250 and 380 miles
More of an expedition than a race, the 6633 is an arctic ultra, with three different distances: 120 miles, 250 miles and 380 miles. As you can expect, it’s really rather cold in the arctic, with temperatures ranging from -5 to -50. It’s also a self-sufficient race, and most people will pull along a sledge with their tent, sleeping bag and food and drink on.
This is a truly unique race and will invigorate runners with a deeply rooted need to explore.
Hurt 100
100 miles
Distance: 100 miles
Location: Honolulu, Hawaii
The Hurt 100 trail race was created by a group of runners with a desire to put Hawaii on the map as a race destination, and show off their wonderful trails. In 2001, the first 100 mile race took place – there were only eight finishers. It soon became known as one of the hardest 100-mile races.
Hundreds of runners apply every year but only 135 lucky people get to take the trials – and they have 36 hours to complete it.
The Barkley Marathons
100 miles….supposedly
Distance: 100 miles… supposedly
Location: Frozen Head State Park, Tennessee
In 2024, the first women ever crossed the finish line of the Barkley Marathons, and in race history, only 20 people have ever finished – a testament to just how hard this race is. The Barkley Marathons is composed of five 20 mile (though some suggest it’s closer to 26 miles) loops, with 3500m of climbing in each. On each loop, runners must find a book, using a map of Frozen Head State Park, and tear out a page corresponding to their bib number. If they turn up without the page, the race is over. Dense forest makes this race hard to navigate, coupled with mud, brambles and elevation.
To add another layer, runners don’t know the start time of the race until the day of the race, when race director Lazarus Lake (Laz), blows the conch shell, giving a 1 hour warning.
It might be the cheapest race to enter in the world ($1.60) but it definitely isn’t the easiest!
Dragon’s Back Race
380KM
The Dragon’s Back Race is a 380km, 60 day ultra, and is considered one of the toughest in the world. Inspired by that of the 1992 race, in which the inaugural Dragons tackled Wales, the course traverses the spine of Wales, from Conwy Castle to Cardiff Castle. Oh, and if you didn’t think the UK had hills, this may change your mind, with over 16,400m of elevation in total. Racing in the UK isn’t like racing in Europe: the terrain and weather combined make for extreme race conditions – this is a race that shouldn’t be underestimated.
Endure24
As far as you can go in 24 hours
If you ever had the urge to see what it would be like to run for 24 hours, then Endure24 is for you. Endure24 takes place in two locations in the UK, Reading and Leeds. Both courses are on trails and cover a 5 mile loop, which runners are to run as many times as possible within the 24 hours.
What is great about this race is that you can enter it both solo and as a team, which brings a supportive community element to it. It also means if you just want to run one or two loops, you can.
Once coined the ‘Glastonbury for runners’, this is a great event to do if you’re new to ultra running, as you’re never too far away from a checkpoint, and there’s a lot of fun to be had aside from the running, too.
Self Transcendence 24-hour Track Race
As far as you can go in 24 hours
If you thought the 5 mile looped Endure24 course would be hard on the mind, try a 400m track. The Self Transcendence 24 Hour Track Race, has taken place annually in south London every September, since 1989. Each year, a growing number of runners have toed the start line to see just how far they can run in 24 hours.
As the name says, it’s a journey of self transcendence…
Ultra-Trail Snowdonia
20km – 100 miles
The Ultra-Trail series of races is one of the most iconic in the world, thanks to the inaugural Ultra-Trail du Mont-Blanc, which first took place in Chamonix, in 2003.
Now, Ultra-Trail events can be found all over the world, and one of them happens to take place on the highest mountain in England, Snowdonia. There are a variety of distances from 20 km to 100 miles, but as we’re talking about the world’s toughest ultra races, it’s the 100 miler that takes the top spot.
With over 9500m of elevation gain across unpredictable mountains, this is a race set to test even the most seasoned runners.
Ultra-Trail du Mont Blanc
100 miles (plus 15-300km events)
For most ultra trail runners, the Ultra-Trail du Mont-Blanc takes top of the list when it comes to bucket list races. The 100 mile race traverses across three countries, France, Italy and Switzerland, among the shadows of Mont-Blanc.
With 9963m of elevation and a 46 hour and 30 minute cut-off, it’s a true adventure, culminating at one of the most emotional and supportive finish lines in the ultra-trail running scene. Many trail running legends have descended to Chamonix to battle this course, including Jim Walmsley, Courtney Dauwalter, Killian Journet and Katie Schide.
There are also alternative distance races ranging from 15k to 37km, 50k, 100k and even 300km!
Dolomiti Extreme Trail
103KM
Running in the iconic Dolomite mountain range is nothing short of spectacular. The Dolomiti Extreme Trail (DXT) held its first race in 2013 and has come a long way since. It’s still smaller than the bigger race like UTMB, and attracts a lot of local runners, which is somewhat of an allure.
There are a variety of races but the toughest is the 103 km race, which has 6,563m of elevation.
Tour de Géants
330KM
If 100 km isn’t quite long enough for you, then the Tor de Géants (TDG), a 330 km race, in Italy, will certainly test everything you have. Starting in Courmayeur, the race travels west, crossing the valley at Donnas and returning back on the eastern side. The trails are rugged and the weather unpredictable, but the scenery is stunning. This, alongside the supportive locals cheering you along, is what keeps you going.
Marathon des Sables
250KM
Running through sand is usually something most of us avoid, but in the Marathon des Sables, it’s just you against the desert for a sweltering 250 km. Taking place in Morocco, this is a self-sufficient race, which means runners must carry all their equipment and food, except water and a tent, which are provided. The race is completed in 6 stages, ranging from 30 km to 80 km, with long cut-off times, to enable as many people to make it to the end as possible – for such a hard race it actually has a 90% finish rate.
Tick off just one or two of these bucket list races, and you’ll definitely have earned yourself some kudos in the running world! Check out our race guides for more inspiration.
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