LIVE NOW: The Super Bowl of Trail Running Is Underway in the Alps (and Our Minds Are Blown!)

UTMB 2025 is underway in Chamonix. Learn what the Ultra-Trail du Mont-Blanc is, why it matters, and how to watch the toughest trail race.

French runner Ugo Ferrari is welcomed by supporters with flares as he climbs the Notre Dame de la Gorge during the Ultra-Trail du Mont Blanc (UTMB) in Les Contamines-Montjoie in 2024. (Photo: Emmanuel Dunand/AFP)

Sierra Shafer

Updated August 29, 2025 12:50PM

Right now, the world’s best endurance athletes are circling Mont Blanc on foot in one of the most mind-blowing races on Earth: the Ultra-Trail du Mont-Blanc (UTMB). The 106-mile event is underway in Chamonix, France, and you can watch it live for free on Outside TV (and rewatch anytime on Outside+). Outside Run also has an ongoing live blog with on-the-ground coverage you can’t find anywhere else.

If you’ve never heard of UTMB, here’s why this mountain-sport spectacle is worth tuning into, even if you’re not a runner.

What Exactly Is UTMB?

It started in 2003 as a single, jaw-dropping race: 106 miles around Mont Blanc, the tallest peak in the Alps. The course covers three countries—France, Italy, and Switzerland—climbs the equivalent of Mount Everest from sea level, and gives runners fewer than two days to finish.

Since then, it’s exploded into a full festival. Today, UTMB week includes eight different races, gear launches, film screenings, brand parties, and a nonstop crowd of cowbell-ringing fans. For outdoor athletes of every stripe, Chamonix becomes a pilgrimage site.

The Main Event

The race everyone talks about is still the original: the Ultra-Trail du Mont-Blanc (watch it live for free now on Outside TV and rewatch anytime on Outside+).

About 2,300 runners line up to circumnavigate Mont Blanc on foot—106 miles, 33,000 feet of climbing, and 10 alpine summits.

For perspective: that’s four marathons, back-to-back, on mountain trails, often through the night, with a cutoff time of 46.5 hours.

Winning here makes you a legend. American star Courtney Dauwalter has done it three times (2019, 2021, 2023) and is gunning for a fourth. Jim Walmsley became the first American man to win in 2023. For the sport of ultrarunning, UTMB is the crown jewel.

Why It Matters (Even If You Don’t Run)

Even if you never plan to lace up for more than a 5K, this is the kind of event you can’t stop watching. The finish-line footage delivers the type of full-body chills and tear-jerking emotion you usually only get from the very best Olympic commercials.

Sheer spectacle: Watching humans push through 100+ miles in the Alps is both mind-bending and inspiring.
Outdoor culture: UTMB is a gathering place for athletes, brands, filmmakers, and fans across skiing, climbing, and cycling—not just running.
Scenery: The footage is stunning: glaciers, alpine villages, and cowbells echoing through the night.
Feel-good storylines: Americans are finally breaking through, while European legends defend their turf.

French trailer Francois d'Haene and other competitors take the start of the 22nd edition of the Ultra Trail du Mont Blanc (UTMB), a 174km trail race crossing France, Italy and Switzerland, in Chamonix, south-eastern France. — French trail runner Francois d’Haene and other competitors take the start of the 22nd edition of the Ultra Trail du Mont Blanc (UTMB), a 174km trail race crossing France, Italy, and Switzerland, in Chamonix, south-eastern France. (Photo: Jeff Pachoud/AFP)

The Other Races

While UTMB is the headliner, a lineup of supporting events also happened this week, which you can recap in our full guide on Run.

Petite Trotte à Léon (PTL): A 186-mile team trek over unmarked terrain. No winners, just survivors.
Courmayeur-Champex-Chamonix (CCC) and Sur les Traces des Ducs de Savoie (TDS): Brutal “mid-distance” races (62–92 miles) that attract top pros (CCC) and aspiring champions (TDS).
Orsières-Champex-Chamonix (OCC), Martigny-Combe-Chamonix (MCC), and Experience Trail Courmayeur (ETC): Shorter but still beastly races (9–34 miles) that range from international-level distance runners to locals, volunteers, and even rising stars taking a shot at the stage.
Youth Chamonix Courmayeur (YCC): A two-day race for teens ages 14–19, like the Little League World Series—Alpine edition.

All of these races end in Chamonix, greeted by roaring crowds and a finish-line energy that feels more like a rock concert than a running race.

At the Ultra-Trail du Mont-Blanc, athletes race 106 miles around Mont Blanc, surrounded by some of the most scenic trails in the Alps. (Photo: Michel Cottin/Agence Zoom)

How to Watch

Stream it live for free on Outside TV.
Catch replays anytime on Outside+, so you don’t miss the finish.
Want the full race-by-race breakdown? Read our UTMB live blog on Run.

Bottom line: UTMB is more than a race. It’s a mountain-sport phenomenon that turns a quiet ski town into the beating heart of endurance culture for one unforgettable week, and it just might motivate you to close your laptop early today and get outside. Inspired by what you see? Check out our complete beginner’s guide to trail running. Winter more your thing? Here’s how to ski Chamonix like a pro.

Sierra Shafer

Sierra Shafer is Editorial Director of Lifestyle at Outside, overseeing SKI, Backpacker, Climbing, Yoga Journal, Triathlete, and Run. She was formerly the Editor-in-Chief of both SKI and POWDER magazines. She was raised in Colorado near Rocky Mountain National Park and has since lived and traveled around North America, Europe, and South America to find and tell stories about skiers. Skiing in Japan is still on her list. When she’s not skiing, you’ll find her rollerblading, mountain biking, or hiking with her dogs near her home in Salt Lake City, Utah.

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