Trail Running calendar near Boulder 2026-2027

Trail races and a family adventure run on Philip S. Miller Park and Ridgeline Open Space, offering 5K, 10K, half marathon and a 50K ultramarathon.

A six-hour trail challenge in Littleton where runners complete a 5K each hour for six hours, totaling 18 miles if completed. Trail terrain, hourly elimination, tiered patches and medals, and national leaderboard prizes highlight the format.

Multiple trail distances at Staunton State Park on October 10, 2026, from a steep 5K to a 50K ultramarathon, plus a 25K FishSlappers division that includes catching a trout; proceeds support conservation organizations.

A loop endurance event near Castle Rock, Colorado honoring two women with long lives. Choose **104 miles** or **52 miles** on a 3.25-mile loop, with solo and relay options plus camping, food trucks, and live music.

Run the Rocks is a fundraising event at Red Rocks Park and Amphitheatre in Morrison, Colorado on October 11, 2026. It offers a 5k and a 1.3 mile family course and raises funds for lung disease education, advocacy and research.

Indian Creek Trail Runs in Sedalia, Colorado on October 17, 2026 offers multiple trail and ultra distances through montane forests, aspen groves, red rock formations and prairie vistas with city views from several viewpoints.

Trail marathon and half near Fort Collins along redstone singletrack and technical rock sections, with stocked aid stations, drop bag options, and caps of 400 entries per distance.

Trail races at Bear Creek Lake Park offering 5 miles or a two-lap 10 miles on single-track dirt. Registration includes park admission, a finisher meal and refreshments; 10 mile finishers receive a commemorative mug.

Trail races at Bear Creek Lake Park on Oct 25 2026 featuring 5 km, 15 km, a 5+15 double and a Kids 1 km. Mostly dirt single and double track with steep climbs, marked courses and included postrace items for adult distances.

MonsterDASH Louisville on Oct 25, 2026 offers a new half marathon plus 5k, 10k and a kids mile with costume contests, expo, and themed runner perks.

A Halloween themed 5k and 10k through historic downtown Erie and Coal Creek trails, with a kids Goblin Run and BOLDERBoulder qualifier status. The event supports the Erie Optimist Club as its primary fundraiser.

Experience 13.1 miles of singletrack trails and hills in the Highlands Ranch Backcountry Wilderness Area. Enjoy custom medals and a post race pancake breakfast while competing for cash prizes in various categories.

Timed 6-, 12- and 24-hour running and relay events on a certified 1.0002 mile dirt loop at Colorado Youth Outdoors Swift Ponds in Fort Collins, with full-service aid every lap and locker-style lodge support nearby.

Trail races in Louisville Colorado offering a half marathon, 10K and 5K on dirt trails with views of the Flat Irons and on course aid stations.

The Sawmill Trail Runs will take place in Conifer on Saturday 5 December 2026. You can run 50 kilometers.

Eight hour ascent on the Thumb Open Space trail in Estes Park, CO with a 1 km out and back course, poker chip scoring, milestone patches, and a 30 participant limit.

A long-distance event on April 11, 2027 along the Poudre River Trail offering 50- and 100-mile solo and relay options through Bellvue, Fort Collins, Timnath, Windsor and Greeley.

A multi-distance trail event at Greenland Open Space near Larkspur, Colorado on May 1, 2027, featuring 50K, 25K, 8 Mile and 4 Mile courses on dirt double-track trails with aid stations and looped routes.

Trail races near Fort Collins offering 25 and 50 mile options on mostly singletrack through Lory State Park and Horsetooth Mountain Park, featuring about 5,500 ft or 11,000 ft of vertical gain, staffed aid stations, and marked trails.

Trail races at Mueller State Park from 10k to marathon plus two 12 hour timed events that use colored ball draws to set loop sequences. All courses are single and double track with no pavement and feature an aid station.