Its origins may stem from Ancient Greece, but the marathon run is still a distance that captivates and inspires athletes in the 21st century.
It's one of endurance sport's ultimate challenges and it's a distance not to be sniffed at: some 26.2 miles/42.2km where smart pacing is paramount, a nutrition strategy is mandatory and serious pre-event training is performed to avoid bonking at the dreaded 18-22 mile segment, often named 'The Wall'.
But don't let us put you off, finish one and you'll remember it forever (and don't feel shame about bragging about it a bit, too).
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While marathon distances are largely standardised, the course elevations, underfoot terrain and weather conditions are not. Trail marathons, mountain marathons, fell marathons, road and trail combos, and more all fill the marathon calendar worldwide.
But which is the toughest? Here's our pick of the best UK and international marathons for you to be inspired and awed by, and perhaps even enter. Just don't forget the blister plasters...
Toughest marathons in the UK
1. Endurancelife Exmoor, Devon
When: 9 May 2026
Where: Martinhoe, Exmoor
Endurancelife have been offering hugely testing coastal trail runs around the UK for years, but this marathon-length brute in Exmoor has long been seen as their toughest challenge.
Exmoor is an underrated and hilly devil: a land of towering sea cliffs, rugged moors and wooded combes, all of which feature on this 26.7-mile Exmoor beast.
Starting near Martinhoe in the quieter western area of one of England’s least visited and smallest national parks, the route includes stretches of the South West Coast Path at its most vertiginous in Countisbury and the Valley of the Rocks, as well as deep inland valleys. And all on an unforgiving underfoot terrain of rocks, grass and forest trails.
The mighty elevation gain of 1,850m ensures a long day out at both ends of the field, with the winners coming home in around four hours and the final athletes close to the eight-hour mark. Don’t forget your blister patches….
If you want a taster before you romp home in the marathon next season, Endurancelife also offer a 6.3-mile (10km) option in Exmoor. Admittedly, with 451m of climbing, it’s still a brute where most of the field will take well over an hour to finish, but those Bristol Channel views should soften the pain somewhat.
2. Snowdonia Trail Marathon Eryri, North Wales
When: 11-12 July 2026
Where: Llanberis, Wales
With a mighty 1,685 metres of elevation gain over its 27.3-mile route, this Eryri/Snowdonia-set corker jostles with Endurancelife Exmoor as the toughest trail marathon in the UK.
The route circumnavigates and eventually climbs Wales' highest peak of Yr Wyddfa (Snowdon) before the leg-shaking descent back into Llanberis for one of marathon racing’s most welcome finish lines.
And if that doesn’t sound tough enough for you, Always Aim High also organise the Slateman Ultra Triathlon in June, with a 2.4-mile swim and 112-mile bike before the marathon run.
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3. Eden Marathon, Cornwall
When: 18 October 2026
Where: The Eden Project, St Austell, Cornwall
I ‘raced’ Cornwall’s Eden Marathon in 2023 and didn’t check the total elevation gain… until after I’d entered. Big mistake, as the mighty 1,000m of climbing over the 26.2-mile (42.2km) course puts at the top end of the UK’s major marathons and left me a shuffling shell of a man by the 20-mile mark – the half-marathon option would’ve been a wiser choice.
It was worth the golf ball-sized blisters, though, with the relentlessly rolling route taking in Cornish clay country, an epic climb to Helman Tor and the Eden Project’s famous biodomes at the finale (your supporters also get free Eden entry on the day).
The multi-terrain course largely takes place on country lanes and trails – I’d advise road shoes with decent grip or less aggressive trail running shoes if the weather has been largely dry before the race.
And did I mention that you get a free Cornish pasty and a can of Doom Bar at the finish? I’ll see you there in October.
4. Langdale Marathon, Lake District
When: 17 October 2026
Where: Langdale, Lake District, Cumbria
This Lake District race is regularly labelled as the UK’s toughest road-based marathon due to its hilly course with 1,036m of elevation gain thanks to its double ascent of Blea Tarn. There’s also typically a high Did Not Finish (DNF) rate, with a study from New Balance placing drop-outs at 15% in 2022.
5. Ultra X Scotland
When: 2-3 May 2026
Where: Fort Augustus/Loch Ness, Scotland
While admittedly not a marathon, the Ultra X Scotland 50km is the perfect race for marathon lovers who are ultra-curious to dip their toes into the world of ultra running. I may be biased, though, as this is exactly what I did a few years back.
Coming from a road marathon running background, I was in for a painful yet spectacular treat running alongside Loch Ness on this point-to-point race where you're enveloped in the wild hills and glorious scenery of the Scottish Highlands.
The 50km race is the final leg for multi-stage athletes (there are 110km, 60km, 25km, and 12km events), whom you can spot a mile off from their dogged stride and determined grit on their faces, but for 50km competitors it's a brilliant route across varied and undulating terrain.
The biggest hill immediately greets runners from the get-go, but once surmounted, the views are magnificent and continue all the way to the finish at Dores. Expect to run around 51km with an overall elevation of 1,439m. Review by Kate Milsom
The world’s toughest marathons
The UK might offer some of the most consistently hilly terrain for runners, but the toughest worldwide contenders also throw high altitude and extreme weather conditions into the marathon mix. Plus, marathon getaways make an ideal excuse to whisk the family off on a far-flung vacation and bag you a support crew for the race.
6. Inca Trail Marathon, Peru
When: 24 May 2026
Where: Cusco, Peru, South America
The Inca Trail Marathon in Peru takes runners back in time to a 500-year-old hand-laid cobbled path. Some 10,400 ft of elevation gain and four major mountain peaks stand in the hardy entrants’ way, with many taking up to 16 hours to complete the formidable challenge.
7. Pikes Peak Marathon, Colorado
When: 19-20 September 2026
Where: Manitou Springs, Colorado, USA
The Pikes Peak Marathon in Colorado is the oldest continually held marathon in the USA and takes place on a mix of rocky, narrow, and winding gravel tracks. Many runners take 8-10 hours to complete the marathon, slowed further by the brutal 2,382m of elevation gain.
8. Kilimanjaro Marathon, Tanzania
When: 22 March 2026
Where: Moshi, Tanzania, Africa
With a highest point of 4,206m, the Kilimanjaro Marathon in Tanzania, Africa, is the highest organised marathon in the world and witnesses finishing times run up to 20 hours. Temperatures can drop below freezing at night, but there’s no cut-off for finishing. This year, the race is an official Comrades qualifier.
9. The North Pole Marathon
When: 12-27 July 2026
Where: The Geographic North Poles (a boat trip from Longyearbyen, Svalbard)
A trail marathon with a twist, the North Pole Marathon is actually the only marathon in the world where you run on water, or ice flows, for the entire duration. The northernmost marathon on earth, this is not a race you'll forget in a hurry – nor let your friends forget either!
The race (there are spring and summer editions) comes as a package with transport involving flying first to the capital Norweigen Svalbard archipelago of Longyearbyen before boarding a ship to sail amongst glaciers due north. Participants will be transported to the geographical north pole (90 degrees north latitude) on the Arctic ice floe, for the start of the marathon.
Afterwards, participants can celebrate with a Polar plunge and more sightseeing of the unique landscape on this once-in-a-lifetime trip. Runner Carl Philips, USA, remarks on his North Pole experience: "This was the greatest running adventure of my life. I've run at sea level and on 14,000ft mountain tops. In 35 years as a runner, nothing comes close to the extreme conditions experienced in the North Pole Marathon."
10. Big Five Marathon
When: 13 June 2026
Where: Entabeni Game Reserve, South Africa
Explore the sandy trails of the wild Entabeni savannah during the Big Five Marathon. Yes, it's exactly as it sounds – this 42.2km running race (also a 21.1km event) will lead you through some of the most diverse and challenging terrain in the world, habitat to the big five: rhino, buffalo, leopard, lion, and elephant.
The big five is coined as such because they're known historically as the most dangerous and difficult animals to hunt. These days, they're considered five of the most dangerous predators in the world. Don't worry, though, the race is fully policed with game drivers and runners have praised the camaraderie and support.
One runner adds: "A very challenging marathon, that makes you feel as if you become one with the wild nature, offering you the ultimate sense of freedom."
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