Run one of the fastest-growing, top-rated marathons in the country!

Boulderthon was named one of the Top 5 Best Half Marathons in the United States by Active. Their take: “Racing in Boulder, Colorado, should be on every runner's bucket list, and the Boulderthon [Marathon] might be the perfect way to cross it off.

The course starts at Boulder Reservoir, which gives you a true sense of Colorado's scenic beauty. Then you run along the foothills of the Flatirons. Finally, you wind your way into downtown Boulder and finish on the historic Pearl Street Mall. Veteran runners have touted this as one of the best race events of their lives; it has all the amenities of a big race (gear check, pace groups, plentiful aid stations) with the charm and attention to detail of a small race. Plus, it's a downhill finish!”

Tucked into a stunning valley below the iconic Flatirons, Boulder, CO sets the backdrop for the top-ranked marathon race series, which features a Half, Full, 5k, 10k, and Kids Run. Boulder is a world-class destination offering 300 days of sunshine and endless recreation, shopping, dining, cultural and entertainment choices. It's no wonder National Geographic named Boulder the Happiest City in America.

Boulderthon typically sells out, so we recommend registering well in advance for this one.