Congratulations to the 4,000+ Boulderthon 2022 Finishers! View Results & Photos here.
aerial view of Boulder streets


Running is the heartbeat of Boulder — one of the three hallmark recreational activities of our community (along with cycling and hiking, of course).

Together, we run the streets & trails of Boulder, and serve as one of the great training grounds for Olympians, world-class athletes, and leisure runners alike. We are so grateful & proud to have the world's best 10k — but despite running being hardwired into Boulder’s DNA — we have no signature city marathon.

This was the question we asked everyone — and we couldn’t find out why.

In one of the great health meccas of the US, rated one of the healthiest, happiest cities in the country, we couldn’t find a premier, signature marathon.

After years in the making and the opportunity to acquire a 19-year-old race series, the Boulder Backroads Marathon & Half Marathon, we knew the time was now. As residents of Boulder County and local business owners, our goal from day 1 has been to create an inspiring, community-driven marathon series to serve as the premier fall race in the state. We decided to create the epic, downtown marathon race the beautiful city and community of Boulder deserves.

Boulderthon® was born.

Boulderthon 2023 will take place on Saturday, October 7th and Sunday, October 8th 2023. The top-rated races became the second largest marathon series in Colorado in its first year of existence, and the largest full running event in the state.

In its second annual edition, Boulderthon is on track to nearly triple in size, drawing runners from all 50 states as well as 15 countries, as the signature city marathon showcases Boulder’s beautiful downtown and spectacular views of the Flatirons.