Trail Running calendar near Boulder 2025-2026

The Indian Creek Trail Runs, part of the Human Potential Running Series, is an annual fall trail running event held at Indian Creek Campground in Sedalia, Colorado. Celebrating its 12th year in 2025, the race offers multiple distances: 5-Mile, 15-Mile, 55k, and 50-Mile, with time limits of 12 to 14..

The Great Trailhead Foot Race 10 Miler takes place at Bear Creek Lake Park in Lakewood, Colorado, offering runners a scenic trail experience with single-track dirt paths against the backdrop of Denver's skyline. Participants can choose between a 5-mile or a challenging 10-mile double-lap course. Reg..

Beware The Bear Trail Races take place at Bear Creek Lake Park in Lakewood, Colorado, offering 5km, 15km, and a combined 5+15km double race, along with a 1km kids' run. The courses feature mostly dirt trails with a mix of single and double tracks, incorporating short steep hills, rollers, and varied..

The Colorado 24 Hour Run, held in Fort Collins, Colorado, offers a unique endurance running experience on a scenic, flat one-mile dirt loop. Participants can challenge themselves in various timed events including 6, 12, and 24-hour runs, as well as relay options for each duration. The course is desi..

The BINGO! Trail Party is a unique trail running event held at May Farms in Byers, Colorado. It offers multiple distance levels ranging from 6 to 54 miles, with a distinctive bingo-style format where runners complete loops and mark numbers on their bibs based on bingo balls drawn after each loop. Th..

The HRCA Backcountry Wilderness Half Marathon is an annual 13.1-mile trail race held in Highlands Ranch, Colorado, featuring a scenic single-loop course through the Douglas County East/West trail and the Backcountry Wilderness Area. The race offers a challenging route on dirt, gravel, and singletrac..

The Louisville Trail Race, held annually in Louisville, Colorado, features a half marathon, 10K, and 5K on scenic front range trails. Celebrating its 12th year, the event offers mostly dirt trail courses with gentle elevation gains and challenging hills that provide stunning views of the Flat Irons..

The Thumbs Up Vertical Challenge is an 8-hour ascent race held in Estes Park, Colorado, on the Thumb Open Space trail. Participants repeatedly run a 1 km out-and-back course with a 540-foot elevation gain per ascent. Runners collect poker chips at the turnaround point to track their completed ascent..

The Sawmill Trail Runs is an annual trail running event held at Staunton State Park in Pine, Colorado, approximately 40 miles southwest of Denver. Scheduled for December 6, 2025, the race offers three distance options: 8 miles, 16 miles, and a 50k ultra-distance. The course features scenic and chall..

The USCSA Cross Country Ski Racing Festival, held at Snow Mountain Ranch Nordic Center in Granby, Colorado, is a vibrant collegiate and junior skiing event scheduled for January 24-25, 2026. It features classic races of 15 km and 7.5 km for college and independent high school athletes, alongside CHS..

Run the Ranch is an annual trail running event held at the scenic Sylvan Dale Guest Ranch in Loveland, Colorado. The race offers a variety of distances including 5K, 10K, and timed trail runs of 4, 6, and 12 hours, with options for solo runners and 4-person relay teams. Participants run on private r..

Niwot's Challenge is a unique, invitation-only endurance event held annually near Sedalia, Colorado, along the South Platte River in the Front Range. Unlike typical races, it emphasizes self-reliance, navigation, and mental toughness over speed. The course is a secret, off-trail gauntlet requiring m..

The Greenland Trail Races, held annually in May at Greenland Open Space in Larkspur, Colorado, offer four race distances: 4 miles, 8 miles, 25K, and the 50K ultramarathon, known as Colorado's fastest 50K. The course features wide, smooth dirt trails through native grasslands, oak hills, and ponderos..

Endure Trail Runs, part of the Human Potential Running Series, is held annually at Mueller State Park near Divide, Colorado. The event offers multiple distances including a unique 12-Hour timed run, a marathon, half marathon, and 10k, all featuring scenic courses on double-track and single-track tra..

The Summits Trail Runs, held at Granby Ranch Resort in Colorado’s Rocky Mountains, offer a challenging series of trail races with distances from 6 miles to ultra distances including a 50k and a 12-hour Elevation Challenge. The courses feature rugged alpine terrain, single-track trails, alpine meadow..