Registration for Boulderthon 2023 is now open! After nearly tripling in size and selling out last year, Boulderthon has instituted a new 5,000 runner cap and is expected to sell out again this year. Register today.
marathon participants reaching the finish line

Boulderthon is One of the Top-Rated Half Marathons in the United States

In 2023, Active named Boulderthon as one of the Top 5 Best Half Marathons in the United States.

“Racing in Boulder, Colorado, should be on every runner's bucket list, and the Boulderthon Half 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 picturesque valley below the iconic Flatirons, Boulder, CO sets the backdrop for the top-ranked, signature Boulder Marathon, Boulderthon. 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.

In its second annual edition, Boulderthon drew runners from all 50 states as well as 15 countries, as the signature marathon showcased the world-class city of Boulder set at the foothills of the spectacular Flatirons.

Join us on Sunday, Oct 8, 2023 for the 3rd annual Boulderthon Marathon in stunning Boulder, Colorado. The course starts at Boulder Reservoir, and takes you through the beautiful back roads of Boulder, Colorado at the foothills of the Flatirons, before winding you to Downtown Boulder for an epic, one-of-a-kind finish on the historic Pearl Street Mall! Boulderthon is a certified Boston Qualifier and is the perfect fall race to enjoy Boulder, Colorado, named the happiest & fittest city in America.

After nearly tripling in size last year and selling out, Boulderthon has instituted a new 5,000 runner cap this year and is expected to sell out again.


Boulderthon Half Marathon Information

Date: October 8, 2023

Start Time: 7:30am

Course Close: 2pm

Elevation Gain: 525 feet

Course Map:

Course Map

Boulderthon Half Marathon Registration

Registration for the Boulderthon Marathon is open. You can register online or show up early and register on the day of the race.

Boulderthon also offers a Kids Run and 5k on Saturday, October 7th. On Sunday, October 8th our other races include a 10k and Marathon.


Race Packet Pick Up:

  • Boulderthon offers Early Packet Pickup (open to all) beginning Saturday, 9/30/23 through Thursday, 10/5/23 at Boulder Running Company, 2775 Pearl St, Boulder, CO 80302, during their normal hours.

  • Our Official Expo & Packet Pickup will take place on Pearl St Mall between 14th & 15th, on Friday, 10/6/23, from 2pm-6pm, and Saturday, 10/7/23 from 10am-4pm.

Getting There:

  • All Half Marathon runners will choose a transportation option (either Shuttle or Runner Drop Off Pass). Shuttle Transportation is for the Half & Full Marathon only. Shuttles depart from Boulder High School beginning at 5am and transport Half & Full Marathon runners to the Start Line at the Boulder Reservoir. Shuttle rides are approximately 20 minutes.

  • Due to space restraints at Boulder Reservoir, all runners being dropped off at the Reservoir will require a Runner Drop Off Pass. No drop offs are allowed without a Pass.

Where Do I Park?

Whether you are boarding our Shuttle at Boulder High School (limited parking is available at Boulder High School on Race Morning) or planning on cheering runners on Pearl between 15th and 17th, here are the BEST FREE GARAGES to park in on Boulderthon Race Weekend.Parking Map


Gear Check

  • Your Goodie Bag is your Official Race Check Bag
  • Gear Check is available at the start
    • Please bring your Official Gear Check Bag to the Start and safety pin your Gear Check Tear-Off at the bottom of your bib to the top of your Official Gear-Check Bag.
  • We will transport anything you put in your Official Gear Check Bag to the Finish Area for you.
  • Please plan for chilly weather! Colorado can be chilly in October, with lows of 40 degrees in the morning. Plan on extra layers and check them into your Official Gear Check Bag.

Course Support

  • There will be water stations near miles 1.5, 2.5, 6, 7.5, 9, 10.5 and 12.
  • Skratch Labs Hydration Mix will be available near miles 6, 9 and 12.
  • The Skratch Labs Hydration Mix flavors will be Lemon Lime & Fruit Punch.
  • Port-a-Potties will be available on the course near miles 1.5, 2.5, 6, 6.5, 7.5, 9, 9.25, 10, 10.5 and 12.
  • A number of highly trained physicians, nurses, physical therapists and other medical personnel will be on hand throughout race weekend. There will be medical stations near miles 6.5, 9 and 10, with a comprehensive set-up in the runner services area at the finish line. There will be a number of mobile units moving throughout the course. These units will be staffed by paramedics, EMTs and marathon staff. There will also be ambulances stationed at the finish line and throughout the course.

After Party & Cheer Spots

  • Cheer runners on at the Finish! First 250 spectators will get cowbells. Join the fun at Pearl & 15th St, including our first-of-its-kind finish at the Pearl Street Mall!
  • You can also cheer runners on throughout the course at any of our Hydration Stations!
  • In addition, our Designated Cheer Stations will be:
    • Pearl Street Finish- between 15th & 17th
    • Valmont City Park (on Multi-Use Path)
  • Official After Party is at Avanti F+B, at Pearl & 15th.

Boulderthon Half Marathon Reviews

"This was by far one of the best races I’ve participated in - Aid stations were dispersed well and there was so much help and encouragement from the volunteers and police officers. Thank you thank you thank you." - Miranda
"Fun course, positive vibes, beautiful views and just enough support along the way. Thanks to all who helped make this race happen. I’ll be back every year. Perfect Race." - Jess
“I've run nearly 50 marathons and/or half marathons and this ranks among the very best. Race day execution was flawless and I echo the previous comments about the professional staff and well organized volunteers groups. Looking forward to next year already!” - Brad