When UTMB Group started the OCC 5O-kilometer race in 2014, it was intended to throw a bone to Switzerland.

Previously during the UTMB Mont-Blanc festival of trail racing, hundreds of runners merely passed through the French-speaking Swiss canton of Valais in the Ultra-Trail du Mont-Blanc and CCC 100K on their way to the finish line in Chamonix, France. Although starting a new race in the municipality of Orsières was more of a business relationship and tourism-building opportunity than it was to create a high-level race through Champex-Lac and on to Chamonix, Orsières-Champex-Lac-Chamonix (OCC) has become one of the marquee races in the sport of ultra-trail running.

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The OCC 50K race—which is officially 57.7K long (or 35.8 miles) with 11,500 feet of elevation gain and descent—kicks off the UTMB World Series Finals at 8:15 A.M. local time (2:15 A.M. ET) on Thursday, August 29. The race starts at an elevation of about 2,900 feet in Orsières and then sends runners over three large climbs to the high point of about 7,200 feet at the Col de Blame, a mountain pass near the 20-mile mark of the race just inside the French border. From there, it’s a 7-mile, 3,000-foot descent to the French village of Argentière, followed by one more big climb—a 3.5-mile, 2,000-foot grind to 6,200 feet atop the La Flégère ski resort—before a final 4-mile, 3,000-foot descent to the finish line in Chamonix.

It’s the shortest, most technical, and fastest race of the UTMB Finals as well as arguably the most exhilarating to run or to watch.

“It’s just crazy how much faster it’s gotten,” says American Dani Moreno, who finished third in the 2022 women’s race but then succumbed to illness and dropped out last year. “You’re racing from the gun. It’s a very intense race as we saw last year. And more with the OCC than any other race, a lot of the podium results are decided in the last descent, which makes the race extra exciting.”

After a brief change to last year’s slightly milder course, this year’s route returns to the original course that was last used in 2022. It once again features a semi-technical 4-mile, 2,300-foot climb out of the Swiss community of Trient before the high point on the Col de Blame. Two years ago, there was a fast and furious pack of about 20 men in the lead group running out of Trient, but the climb busted several runners who eventually dropped out at the Col de Blame aid station.

“I think it’s going to change a lot of the dynamics of the race,” says American Jeshrun Small, who was fifth in the men’s race last year.  “I think it’s going to be really tough for a lot of people and the race day weather looks like it will be hot, so it’s going to be tough. Just like every year it’s going be fast from the start and you kind of have to hold on and hopefully it’s your day. There are only a few athletes capable of being out of the top five and coming back to finish on the podium, so  you kind of  have to have it be your day from the start.”

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Women to Watch

Dani Moreno is the second-ranked runner in the OCC 50K, according to the UTMB Index. She dropped out of last year’s race due to illness, but she’s since come back with a vengeance. She won the 50K at the Kodiak Ultramarathons by UTMB in Big Bear, California, last October, then won the Canyons by UTMB 50K in Auburn California, in late April. She didn’t have a great experience at the Zegama-Aizkorri Marathon in May, but then finished a solid fifth in the shorter and faster 21K race at the Broken Arrow Skyrace in California in mid-June.

French runner Clementine Geoffray is the top-ranked runner based on the Index, and her results show she knows how to perform when it matters most. She won the 50K at the World Mountain and Trail Running Championships last June and broke the tape at the lower-profile MCC 40K last year during UTMB Mont-Blanc week. This June, she won the 58K race at the European Trail Running Championships and the 33K X-Trail race in Courchevel, France, on August 4. Swiss orienteering and trail running legend Judith Wyder should also be a contender in the women’s race, having earned the silver medal in the 50K race at last year’s World Mountain and Trail Running Championships, and more recently taking second in the 20K mountain running race at the European Championships and first at the Mont-Blanc Marathon in early July.

China’s Mia Yao, third in the OCC 50K last year, returns, as does New Zealand’s Caitlin Fielder (fourth last year), while Spain’s Sara Alonson, one of the top runners in the Golden Trail World Series, is in the field after winning the lower-profile ETC 15K race last year during UTMB Mont-Blanc week last year.

Italy’s Elisa Desco, who won the 20K race at the Lavaredo Ultra Trail event in Italy in late June, and Americans Allie McLaughlin and Tabor Hemming are among the other top entrants. McLaughlin, the 2022 mountain running world champion, was the early leader in the OCC 50K in both 2022 and 2023 but perhaps burned the candle a bit too hot early on and wound up sixth in 2022 and 14th last year. Hemming was third at both the Canyons 50K and Broken Arrow Skyrace 20K races this spring.

Men to Watch

The men’s race figures to be a battle between about seven runners, headlined by 2023 OCC champion and 2022 CCC 100K runner-up Jonathan Albon of the UK. Albon had been focused on longer races earlier this year—he won the Transvulcania 100K on May 11 in the Canary Islands and then placed a solid sixth at the Western States 100 on June 30—but he’ll no doubt be in the mix on the shorter, punchier OCC course.

American Eli Hemming has been focused on OCC all season. He won the Black Canyon 50K in Arizona in February and the Canyons 50K in California in April before finishing a close second in the Broken Arrow Skyrace 21K in late June. “This is kind of the big show. This is what I’ve been aiming for all year,” Hemming said. “I’m gonna race the race and see what happens. I’m gonna see if I can get that W.”

Remi Bonnet, the 2022 Golden Trail World Series champion, is racing OCC for the first time. He broke Matt Carpenter’s 30-year-old Pikes Peak Ascent course record last year in Colorado, and also won Mont-Blanc Marathon in Chamonix and the Mammoth Trail Fest 26K last year in California. He’s been running well this year, most recently winning the Restonica Trail 50K in France in early July.

Italy’s Francesco Puppi handily won the Chuckanut 50K in Washington and the Lake Sonoma 100K in California in April, but then struggled with fatigue for a month after returning to Europe. He placed eighth in the Mont-Blanc Marathon and 15th at the Sierre-Zinal 31K two weeks ago in Switzerland. The UK’s Robbie Simpson, sixth in the OCC last year, should be a top contender after his win in the Eiger Ultra-Trail by UTMB 50K a month ago in Switzerland, while Spain’s Antonio Martinez Perez, third last year in the OCC, is coming off a win at the Lavaredo 5OK.

Others to watch include Switzerland’s Martin Anthamatten, France’s Benjamin Roubioul, and American Jeshrun Small, who are all ranked among the top 10 in the UTMB Index. Other Americans in the race include Christian Allen, Nick Handel, and Darren Thomas.