The 10 Hardest Endurance Races on the Planet

I've run seven 100-milers and three 200-milers, and I finished Ultraman Arizona. Two races on this list are ones I've done, so I know a little about what "hard" means. The other eight are on a completely different level. Here's my ranking, counting down to the hardest of them all.

At a glance

10. Spartathlon (Greece)

• Distance: ~153 miles (246 km)
• Time limit: 36 hours
• When: Late September

Spartathlon follows the legend of Pheidippides, the Greek messenger who ran from Athens to Sparta in about a day and a half to ask for help before the Battle of Marathon. Runners cover roughly 153 miles from the Acropolis to Sparta, climbing over Mount Parthenio in the middle of the night.

What makes it brutal is the cutoffs. There are about 75 checkpoints, and every single one has its own cutoff time, so you can't start slow and make it up later. At the finish, runners touch the foot of the statue of King Leonidas in Sparta.

9. Ultraman Arizona

• Distance: 320 miles over 3 days
• Time limit: 12 hours per day
• When: March

Ultraman is basically a double Ironman, spread over three days:

Leg	Ultraman	Ironman
Swim	6.2 miles	2.4 miles
Bike	261.4 miles (over two days)	112 miles
Run	52.4 miles (a double marathon)	26.2 miles

Day 1 is the swim and 90 miles on the bike. Day 2 is 171.4 miles on the bike. Day 3 is a double marathon. Each day has a 12-hour limit. I did Ultraman Arizona back in 2023 and finished 4th, and it was a fun one.

8. Cocodona 250 (Arizona)

• Distance: ~253 miles
• Climbing: ~39,000 ft
• Time limit: 125 hours
• When: May

Cocodona is 250 miles across Arizona, from Black Canyon City to Flagstaff. The temperature swings a ton: you start in the low desert heat and climb into the mountains, where nights at altitude get cold. I haven't done this one yet, but I want to.

7. Tor des Géants (Italy)

• Distance: ~205 miles (330 km)
• Climbing: ~80,000 ft (24,000+ m)
• Time limit: 150 hours
• When: September

The Tor des Géants is a loop through Italy's Aosta Valley, beneath some of the highest peaks in the Alps. The elevation gain is the story here: around 80,000 feet of climbing in about 200 miles. That's an insane amount of climbing. It's like going up and down Mount Everest from sea level almost three times.

6. Badwater 135 (California)

• Distance: 135 miles
• Time limit: 45 hours
• When: July

Badwater starts at the lowest point in North America, 282 feet below sea level in Death Valley, in July, when air temperatures can hit 130°F. And it's all on pavement. So it's hot out, but the pavement is also reflecting that heat right back up at you, hot enough to soften the soles of your shoes. It finishes 135 miles later at Whitney Portal, 8,360 feet up Mount Whitney.

5. The Triple Crown of 200s

• Races: Tahoe 200, Bigfoot 200, Moab 240
• Distance: 640+ miles combined
• When: Summer to fall

I did this in 2023, and three 200-mile races in three months is absolutely diabolical. My first two races were only 18 days apart, so I had no time to recover before toeing the line again.

Race	My time
Tahoe 200	86:58:27
Bigfoot 200	79:54:50
Moab 240	91:49:48
Triple Crown total	258:43:05 (6th overall)

Why is it higher on this list than Cocodona? Cocodona is one 250-mile race. The Triple Crown is three 200+ mile races in one season, with almost no time to heal in between. The hardest part isn't any single race. It's lining up for the next one while your body is still broken from the last.

4. 6633 Arctic Ultra (Canada)

• Distance: ~380 miles
• Time limit: ~215 hours
• When: February

The 6633 Arctic Ultra crosses the Arctic Circle in the dead of winter, running about 380 miles up the Dempster Highway from Eagle Plains in the Yukon to Tuktoyaktuk on the Arctic Ocean. Temperatures can drop to –40°, the wind is relentless, and racers pull a sled with all their own food, gear and shelter, with checkpoints sometimes 30 to 70 miles apart. Only a handful of people finish in most years.

3. The Barkley Marathons (Tennessee)

• Distance: 5 loops of ~20+ miles, unmarked
• Time limit: 60 hours
• Finishers ever: about 20

The Barkley is five loops through the backcountry of Frozen Head State Park with no marked trail, where you navigate with a map and compass and tear pages out of books hidden along the course to prove you were there. The race director, Lazarus Lake, is crazy, and he makes the course harder every time someone finishes. In about 40 years, only around 20 people have ever finished it, and nobody finished in 2025 or 2026.

2. Uberman (California)

• Distance: 556 miles
• Format: Swim, bike, run
• Finishers: only a handful, ever

Uberman is an insane ultra-distance triathlon:

• Swim: about 21 miles across the Catalina Channel in the open Pacific, with currents, shipping lanes, jellyfish and sharks.
• Bike: about 400 miles, with 20,000+ feet of climbing, down into Death Valley.
• Run: the full 135-mile Badwater course, from below sea level to Mount Whitney.

Basically, it's Badwater, number six on this list, as the last leg. Only about seven people have officially finished it solo.

1. Self-Transcendence 3100 (New York)

• Distance: 3,100 miles
• Course: 5,649 laps of one city block
• Time limit: 52 days
• Since: 1997

The longest certified footrace in the world: 3,100 miles around a single half-mile city block in Jamaica, Queens. That's 5,649 laps, and to make the 52-day cutoff you have to average about 60 miles a day, every day, for almost two months. The course is open from 6 a.m. to midnight. The record is 40 days and 9 hours.

Running that many miles around one block is absolutely insane. And it's wild that it's been going on since 1997.

Want to take on something hard?

Every one of these athletes started with a first race. If yours is a first marathon or a first 100, here's the complete guide to running your first 100-mile race, and my bucket list 100+ mile races.

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