Trail Running calendar near Boulder 2025-2026

Front Range Ultra Dayze is a multi-day ultra-running festival in Loveland, Colorado, centered at Centennial Park and the River’s Edge Natural Area. Event distances range from 200-mile to 50k, plus timed formats up to 100+ hours, with a 200-runner cap. The flat, fast 2-mile loop traverses mostly dirt..

The Rock Hawk Trail Races take place at Philip S. Miller Park in Castle Rock, Colorado, featuring distances of 50K, 25K, 10K, and 5K. The event is held on the scenic, rolling trails of Miller Park and the Ridgeline Trail systems, offering a course that is not overly technical but still challenging a..

The Calarat Challenge Trail Running Festival takes place in Jamestown, Colorado, at the Cal-Wood Education Center, a nonprofit dedicated to outdoor education. Held over Labor Day weekend, the event features multiple trail races including a half marathon, 10K, 5K, Kids 1K, and combination races like..

Summer Predictor SERIES - Derek Lindstrom is a fundraising running series featuring prediction games tied to two summer races. For 2025, events take place in Leadville, Colorado, and Marquette, Michigan, with the Leadville Trail Marathon (26.2 miles) and the Marquette Half Marathon (13.1 miles). Par..

American Heroes Run takes place in Longmont, Colorado, on a flat, fast loop course of about 1.05 miles. The event features multiple distances, including a 100-mile race (with a 30-hour cutoff), a 24-hour option, marathon, half-marathon, 9.11-mile, and 5K, plus shorter time-limited runs. The atmosphe..

The HRCA Wildcat Mountain Trail Races, held in Littleton, Colorado, offer a scenic and challenging trail running experience through the HRCA Backcountry Wilderness Area. Participants can choose from a 10-mile or 10-kilometer course, both featuring 100% dirt trails with varied terrain and stunning mo..

Black Squirrel Half Marathon is a trail race held at Lory State Park, northwest of Fort Collins, Colorado, with the start and finish at the Soldier Canyon Picnic Area in Bellvue. The 13.5-mile course tour climbs about 1,500 feet to a west ridge around 7,000 feet, then descends and follows roughly 4...

RexRun for PAWSitivity is a pet-friendly trail event in Aurora, Colorado at the Arapahoe County Fairgrounds. It offers a 5K Trail Run, a Family 5K Trail Walk (dogs welcome) and a Kids 1-mile Run/Walk. The day features a pet-centric atmosphere with therapy and patrol K-9 demonstrations, a dog costume..

Cirque Series returns to Arapahoe Basin, Colorado, for a high-alpine mountain race. On White River National Forest trails above Keystone, the course runs about 9 miles with roughly 2,411 feet of elevation gain, starting at Mountain Goat Plaza at the base of A-Basin. Racers ascend via summer road to..

Devil on the Divide is a trail ultramarathon held in Empire, Colorado, offering two distances: 50K and 22K. The 100% dirt, point-to-point courses traverse stunning, remote terrain with views of Clear Creek County and the Continental Divide, reaching elevations above 13,000 feet. The 50K features abo..

The Breckenridge Oktoberfest 5K is a festive trail run held in historic downtown Breckenridge, Colorado, as part of the annual Oktoberfest celebration. Scheduled for Saturday, September 13, 2025, the 5K course winds through the scenic Town of Breckenridge Trails, showcasing beautiful fall foliage an..

Nestled in Old Town Nederland, Colorado (elevation around 8,236'), NedNed Trail Fest offers a long-running trail challenge with three race options: a Half Marathon (about 13.3 miles with roughly 1,408 feet of elevation gain on dirt roads and single-track trails), a 10K (about 6.3 miles on dirt roads..

The Greenland Open Space Pack Burro Race, presented by Double Rainbow Ranch, is the 4th annual event held in Larkspur, Colorado on the Greenland Open Space Trail. It offers two distances: 8 miles and 3 miles, raced by teams of one runner and one burro. The atmosphere blends friendly competition with..

Snow Mountain Ranch Trail Race, held at the YMCA of the Rockies in Granby, Colorado, offers distances for all levels: 50K (31.4 miles), 33K (20.2 miles), Half Marathon (12.8 miles), 10K (6.1 miles), and 5K (3.3 miles). The courses are 100% dirt, featuring out-and-back and looping designs through rol..

Demon Dash is a 5K running or walking event held in Arvada, Colorado, featuring a new dirt course at the NAAC for a fresh home and surface. It’s pitched as a fun, community-focused experience suitable for runners and walkers of all ages. This year, the race runs in conjunction with the Demons Invite..

The Pony Express Trail Run will take place in Woodland Park on Sunday 14 September 2025. You can run between 8 and 16 miles.

The Frederick Pack Burro Race is an annual 10K event held in Frederick, Colorado, celebrating the town's Miners Day heritage. The race follows a scenic course starting downtown at Fifth and Oak Streets, heading north along a trail through a tunnel to the Frederick Recreation Area, looping around Mil..

Red Feather Trail Jamboree is a three-day trail running weekend held near Red Feather Lakes, Colorado, starting from the Ben Delatour Scout Ranch. Runners can tackle three distances: 50 miles (≈8,500 ft of gain), 50K (≈4,200 ft), and a Half Marathon (≈1,700 ft), with a 3-day Challenge totaling about..

Estes Epic is a multi-event trail challenge held in Estes Park, Colorado. The weekend features a 50k bike race, a 50k trail run, a Heavy Half Marathon, and the all-in Epic Double (50k MTB and 50k Run). After a six-year break, the race returns with remote, rugged terrain, single-track trails, steep c..

24 Hours of Palmer Lake is a 24-hour ultramarathon held in Palmer Lake, Colorado, on a 0.82-mile loop atop the Palmer Divide at about 7,240 feet elevation. The event is described as a low-fanfare, community-driven affair, welcoming runners who want to push mental and physical limits in a mountain se..