Trail Running calendar near Boulder 2025-2026

The Alma Foundation Race in the Clouds Dirt Festival is an exciting outdoor event taking place in Alma, Colorado, from July 10 to July 13, 2025. Set at an elevation of 10,600 feet, the festival features a variety of activities including mountain bike racing, trail running, a free kids' race, and an..

The Silverheels Trail Runs, hosted by the Human Potential Running Series, is a premier trail running event held in Como, Colorado, featuring multiple race distances including 10-Mile, 19-Mile, 60k, 50-Mile, 100k, and 100-Mile. The courses traverse stunning high alpine and sub-alpine terrain at eleva..

Chase the Moon is a unique overnight ultramarathon held in Highlands Ranch, Colorado, featuring a 12-hour solo and team relay format (3- or 5-person teams) on the scenic Highlands Ranch Backcountry trail system. Runners experience stunning views of the metro area and Front Range under the full moon'..

The Leadville Silver Rush 50M is a challenging 50-mile trail run held in Leadville, Colorado, featuring 7,503 feet of elevation gain and reaching altitudes up to 12,024 feet. The out-and-back course traverses historic mining roads on the east side of Leadville, offering stunning views of the Rocky M..

The Never Summer 100K and 60K are challenging mountain ultramarathons held from July 25-27, 2025, within State Forest State Park in Colorado. The courses traverse rugged terrain, high alpine ridges, lakes, and peaks in the Never Summer and Medicine Bow Mountains, offering spectacular views and diver..

The Elevation Run/Walk is an annual event held in Conifer, Colorado, featuring race distances of 10 miles, 5 miles, and 2 miles. Set at an average elevation of 8,200 feet, the course showcases the scenic Aspen Park neighborhoods, combining paved roads, dirt roads, and trail running. The event suppor..

The Summit 200 is a challenging 200-mile mountain ultramarathon held in Summit County, Colorado. The race features a single 200-mile loop traversing stunning hiking trails, recreation paths, forest roads, and some pavement, with elevations ranging from over 9,000 feet to nearly 13,000 feet. Particip..

The Sheep Mountain Ultras, part of the Human Potential Running Series, is a challenging trail running event held annually in Fairplay, Colorado. The race offers three distances: a 50-mile ultra, a 50k, and a half marathon, all starting and finishing at the Town of Fairplay Beach. Set at an average e..

The Boulder Rez Marathon, held at Boulder Reservoir in Boulder, Colorado, offers a scenic and mostly flat course with only 200 feet of elevation gain. Runners enjoy trails and dirt roads alongside the reservoir, with stunning views of the water and the Rocky Mountains. The event features multiple di..

The Lory Summer Trail Series is a fun, low-key trail running event held each Tuesday evening in August at Lory State Park, Fort Collins, Colorado. It features a series of shorter races with distances ranging from 5K to 12K, designed to welcome new trail runners and help experienced racers sharpen th..

The Eltuck Valley 5K is part of a series of midweek trail races held at Lory State Park in Bellvue, Colorado. Scheduled for August 5, 2025, this event is designed to cater to both novice and experienced runners, offering a flat and fast course ideal for those looking to improve their speed. Particip..

The Holy COW Trail Stampede is an exciting running event held in Westminster, Colorado, featuring a 10-mile race and 5K/10K options. Participants can enjoy a fun and festive atmosphere while supporting the charity partner, Growing Home, which focuses on breaking the cycle of poverty for families in..

The Run The Rockies Trail Race in Frisco, Colorado, offers 5k, 10k, and half marathon distances along scenic trails on the Frisco Peninsula. The course features single track and dirt road trails with stunning views of Dillon Reservoir and the Ten Mile Range. Starting and finishing at the Frisco Nord..

Dirt Circus - Boulder is a free community running event held in Boulder, Colorado, celebrating local trail running culture. Organized by UltraSignup, this one-day festival features a social group run with options of a casual 4.5-mile or 10K route, allowing runners to connect with the local running c..

The Into the Hills Eltuck 10K is part of a series of midweek trail races held at Lory State Park in Bellvue, Colorado. Scheduled for August 12, 2025, this event is designed to cater to both novice and experienced trail runners, offering a challenging course with significant elevation gain and stunni..

The Leadville Trail 100 Mile Run, held annually in Leadville, Colorado, is a legendary ultramarathon known as the "Race Across the Sky." Established in 1983, this grueling 100-mile out-and-back course challenges runners with extreme Rocky Mountain terrain, starting at 10,200 feet and reaching a peak..

The Into the Hills Eltuck 5K is part of a series of midweek trail races held at Lory State Park in Bellvue, Colorado. Scheduled for August 19, 2025, this event features a challenging course with a steep climb and descent, making it suitable for both novice and experienced trail runners. Participants..

The NoCo Urban Ultra & Relay is a long-distance running event taking place on August 22-23, 2025, along the scenic Poudre River Trail in Northern Colorado. Participants can choose from a 50-mile solo race, a 100-mile solo race, or relay options for both distances, accommodating teams of 2 to 8 runne..

The Arrowhead Half Marathon & 5K is a scenic trail running event held in Arrowhead, Colorado, part of the Vail Trail Running Series. The half marathon covers approximately 13.7 miles with 2,924 feet of elevation gain, traversing trails across Arrowhead, Bachelor Gulch, and Beaver Creek ski resorts,..

The Byers Peak Stampede Half Marathon & 5K Run is an exciting running event set in the stunning Rocky Mountains, just 60 miles from Denver. Scheduled for August 23, 2025, the event features a challenging half marathon and a 5K, catering to athletes of all levels. The courses primarily traverse dirt..