Trail Running calendar near Boulder 2025-2026

The Above the Clouds Ultra is an annual trail running event held in Woodland Park, Colorado, known as the "City Above the Clouds." It features two race distances: a 50K ultra and a 10K run. The course showcases stunning Colorado fall colors and offers fast, flowing singletrack trails around Rampart..

Rocky’s Backyard Ultra is held at the YMCA of the Rockies Estes Park Center in Estes Park, Colorado. Runners must complete 4.167 miles in under one hour each lap, with the field reduced to a single finisher as the race continues until no others remain. The course loops around the boundary of RMNP on..

The Bear Chase Race Endurance Festival unfolds at Bear Creek Lake Park in Lakewood, Colorado, and offers six races: 100K, 50 Mile, 50K, Half Marathon, 10K, and 5K (with a Baby Bear 10K variant). The mostly dirt, single-track course is described as fast by trail standards and not overly technical, wi..

The Suffer Better Fall Trail Run is an annual mountain endurance event held at Staunton State Park, Colorado. The 9th edition, scheduled for October 11, 2025, features challenging courses including 50K and 25K distances, a unique 25K Fishslappers division involving fish catching, and a new 5K race...

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..

Indian Creek Trail Runs, the oldest official race in the Human Potential Running Series, is the Fall Classic held at Indian Creek Campground in Sedalia, CO near Denver. Events include 50-Mile, 55k, 15-Mile, and 5-Mile on single-track trails through Front Range montane habitats—from lodgepole pine fo..

Blue Sky Trail Marathon & Half takes place in Fort Collins, Colorado, on the trails between Horsetooth Mountain Park and the Devil’s Backbone Open Space. Runners choose between the Blue Sky Marathon (26.7 miles with about 3,500 feet of elevation gain/loss) and the Blue Sky Half (13.4 miles with abou..

Beware The Bear Trail Races take place at Bear Creek Lake Park in Lakewood, Colorado. The event offers four distances: 5K, 15K, a 5K+15K double, and a Kids 1K race. The courses are mostly dirt, using single and double-track trails with short, steep climbs, rollers, and rugged terrain, providing a so..

Colorado 24 Hour Run takes place in Fort Collins, Colorado, at 4927 E. County Road 36. The event offers multiple distance options: 24-hour, 12-hour, and 6-hour races, plus 24-hour, 12-hour, and 6-hour relays.Runners complete laps on a one-mile dirt loop—the flat, scenic loop you’ll find in Colorado—..

The Colleen De Reuck XC Classic is a cross country running event held annually at Harlow Platts Community Park in Boulder, Colorado. Honoring renowned distance runner Colleen De Reuck, the race promotes health, fitness, and celebrates local Olympians, with 2025 honoring 2012 Olympic marathoner Yoshi..

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..

Bingo! Trail Party, hosted by the Human Potential Running Series, takes place at May Farms in Byers, Colorado. It features five levels: Level 1 (6–10 miles), Level 2 (8–20 miles), Level 3 (10–42 miles), Level 4 (10–54 miles), and Level 5 (18–54 miles), with a 9 PM time limit and a 300-runner cap. Th..

Louisville Trail Race returns to Louisville, Colorado at Louisville Community Park. It offers three distances: Half-Marathon (13.1 miles), 10K (6.2 miles), and 5K (3.1 miles). The mostly dirt courses traverse scenic Front Range trails with views of the Flat Irons and a couple defining climbs, run as..

Thumbs Up Vertical Challenge takes place in Estes Park, Colorado, on December 6, 2025. The race uses the Thumb Open Space trail, a 2km out-and-back course with 540 feet of vertical gain per lap. The route is 100% single-track with switchbacks, steps and steep rocks, offering views of Longs Peak, Mou..

The Sawmill Trail Runs is an annual trail running event held at Staunton State Park in Pine, Colorado, approximately 40 miles southwest of Denver. The race offers three distance options: 8-Mile, 16-Mile, and 50k, with a combined runner capacity of 250. The course features scenic and challenging terr..

The USCSA Cross Country Ski Racing Festival, hosted by Colorado Mesa University, takes place at Snow Mountain Ranch Nordic Center in Granby, Colorado. Scheduled for January 24-25, 2026, this event features collegiate and junior racers competing in classic and skate sprint races. Distances include 15..

Race The Ranch is a winter snowshoe race held in Granby, Colorado on the Snow Mountain Ranch YMCA property. It offers three distances: 5k (1 lap), 25k (2 laps), and 50k (4 laps), designed to accommodate runners of all levels. The course combines singletrack, doubletrack, and groomed snowshoe trails,..

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..

The Great Western Trail Race, held in Severance, Colorado, offers a variety of running events including a 5K, 10K, half marathon, and a Kids Fun Run. Scheduled for April 18, 2026, this race welcomes participants to enjoy spring racing in a scenic community park setting. The event features chip timin..

Niwot’s Challenge, the 13th annual event, takes place in Sedalia, Colorado along the South Platte River. It isn’t a race but a reckoning, a Barkley-inspired grassroots ultrarunning ordeal of secrecy and mischief. The course is unpublished and largely off-trail—a riddle of rock, bushwhack, and bruise..