4 big, burly Colorado ultra marathons in 2023

Anthony Kunkel #470 reaches the top of Hope Pass after the turnaround during the Leadville 100 trail run
Looking for the ultimate trail running challenge? Check out these four 100-mile races in Colorado in 2023 (Image credit: Daniel Petty / Contributor)

For many trail runners, competing in one of Colorado’s many ultra marathons is the pinnacle of rugged, fast-paced adventures. The state has a long history of trail running, with dozens of ultras each year stretching back decades that take the hardiest of runners across remote mountain ranges at (literally) breathtaking altitudes.

These races are not for the faint of heart – remember that you’ll need a lot more than a great pair of trail running shoes and a positive attitude to take part in any of these races. For trail running in Colorado, you need to be an elite runner with high altitude training and strong navigational skills as well as an understanding of backcountry safety for trail runners in Colorado. Now, without further ado, here are four big, burly Colorado ultra marathons in 2023 for those of you that are tougher than we are.

Trail runners on Vail mountain

For many trail runners, competing in one of Colorado’s many ultra marathons is the pinnacle of rugged, fast-paced adventures (Image credit: Jack Affleck/Vail)

Hardrock 100

 July 14, 2023

The Hardrock is a picture of a ram’s head painted on a block of stone mining debris, and to officially complete this race, you must kiss the ram at the end. Starting and ending in historic Silverton, the Hardrock 100 takes you uphill for 33,197 feet and downhill for 33,197 feet for a total elevation change of 66,394 feet, all at an average elevation of over 11,000 feet. To say you’ll enjoy the views might be overstating things a little, but you’ll run through some of the best of the San Juans, including the gorgeous towns of Telluride and Ouray, the ghost town of Sherman and cross 13 major mountain passes including Handies Peak, a Colorado 14er that delivers the highest point on the course. This unique race kicked off back in 1992 and alternates direction each year. Cutoff time is 48 hours.

Christopher Agby #27 runs down the trail at the Hardrock 100 ultra distance run through the San Juan Mountains

This unique race kicked off back in 1992 and alternates direction each year (Image credit: Daniel Petty)

Ouray 100

July 21, 2023

The Ouray 100 in the San Juans is considered one of the most difficult ultras in the world, but race organizers are clear about one thing: there’s no whining. This is a no-frills, no “everyone’s a winner”, ultra tough run through some of the most beautiful alpine terrain in the world. The race begins and ends near the town’s famous hot springs where you can soak to recover after tackling the grueling course’s 40,000 feet of elevation gain. There’s a 52-hour cutoff for this race, and if you don’t finish, don’t expect a 50-miler consolation buckle. Contact the race organizers (opens in new tab) for information about qualifying. 

Views hiking in the San Juan Mountain range in southern Colorado

(Image credit: Adam Mustafa)

High Lonesome

July 21, 2023

One of the newer races on the calendar, the High Lonesome kicked off just six years ago and takes place on some of the state’s most gorgeous single track on the Sawatch Range in Central Colorado. The Sawatch Range is home to eight of the 20 highest peaks in the Rockies including Colorado’s highest peak, Mount Elbert. The race course begins and ends at the base of another 14er, Mount Princeton and takes you on a loop that covers large swaths of the Continental Divide Trail and the Colorado Trail including five high alpine passes. Total elevation gain is a little less than some other races on this list at just 23,500 feet but you’ve only got 36 hours to complete it, so you’d better be fast. The lottery to enter (opens in new tab) opens in January. 

Woman Hiking to Upper Ice Lakes Basin

The High Lonesome race covers large swaths of the Continental Divide Trail (Image credit: JeffGoulden)

Leadville 100

August 19, 2023

Easily the best-known of Colorado’s hundred milers, the 2023 Leadville 100 will mark 40 years since the first race. Also known as the Race Across The Sky, this legendary 100-mile run started back in 1983 and takes you across extremely rugged and very high terrain around the mining town of Leadville which finds you at elevations between 9,200 to 12,600 feet, climbing and descending 15,600 feet in total. The air will be thin but the views of the Collegiate Peaks are spectacular. If you survive, celebrate with a burger at Wild Bill’s on the main drag (trust us). You have to finish in under 30 hours for a buckle, which is the shortest cutoff time on this list, and if you think you can hang, you can register for the race via lottery (opens in new tab)

Julia Clarke is a staff writer for Advnture.com and the author of the book Restorative Yoga for Beginners. She loves to explore mountains on foot, bike, skis and belay and then recover on the the yoga mat. Julia graduated with a degree in journalism in 2004 and spent eight years working as a radio presenter in Kansas City, Vermont, Boston and New York City before discovering the joys of the Rocky Mountains. She then detoured west to Colorado and enjoyed 11 years teaching yoga in Vail before returning to her hometown of Glasgow, Scotland in 2020 to focus on family and writing.