Run Boulderthon: Colorado's Largest Fall Race Series

Boulderthon was named among the Best Fall Marathons by Runners World, as well as the best Half Marathon in Colorado and one of the Top 13 Most Beautiful Half Marathons in the World by HalfMarathons.net.

Boulderthon has doubled every year since its inception. In its fifth annual edition, Boulderthon drew over 15,000 runners from all 50 states as well as 22 countries, as the signature marathon showcased the world-class city of Boulder set at the foothills of the spectacular Flatirons.

Join us for the largest September running weekend in the U.S. on Sunday, September 27th, 2026 for the sixth annual Boulderthon Marathon in stunning Boulder, Colorado.

The course features an exciting Start downtown with a stunning course through 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 the perfect fall race to enjoy Boulder, Colorado, named the happiest & fittest city in America.

Boulderthon has instituted a new runner cap this year, has sold out every year, and is expected to sell out again.

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Boulderthon - Boulder Marathon - Half Marathon Course Map

Date: Sunday, September 27th 2026

Start Time: 7:00am

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Registration for the Boulderthon Half Marathon is now open.

Boulderthon also offers a Kids Run, 5K & 10K and our Full Marathon!

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Boulderthon offers Early Bib Pickup (open to all) beginning Saturday, 9/20/25 through Thursday, 9/25/25 at 2pm at all Colorado Fleet Feet locations during their normal hours.
- Finisher Shirts will not be available at Early Bib Pickup. Participants who pick up their packet at Early Bib Pickup can pick up their race shirt after they complete their race on Sunday 9/28/25.
Our Official Expo & Bib Pickup will take place on Pearl St Mall between Broadway & 15th, on Friday, 9/26/25, from 1pm-5pm, and Saturday, 9/27/25 from 10am-6pm and Sunday, 9/28/25 from 8am-2:30pm.

This year, Boulderthon features its first-ever Start and Finish Downtown.

Our Start Village is hosted on the Pearl Street Mall, between 13th and 15th.

The Start Line is at 21st and Pearl. The Finish is at 15th and Pearl.

Here are the best ways to get to the Start. For questions, please contact support@boulderthon.org

1. Take an Uber

Use Our Designated Uber Drop Off Lanes

Please enter address 1400 Walnut St, Boulder CO 80302 into Uber (the start of the Drop Off Lanes) to Uber to the Start Village Presented by Uber.

*Note- please use these lanes for all runner drop off.

2. FREE Parking!

Please reference our FREE Parking Garage Map.

Please note, these garages will fill up first and we suggest arriving at least 2 hours prior to the Start.

All parking is FREE in Downtown Boulder on Sundays. See below for the best places to park!

Gear Check is available at the Starting Village presented by Uber Eats
Gear Check Bags will be available at Gear Check
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 late September, with lows of 40 degrees in the morning. Plan on extra layers and check them into your Official Gear Check Bag.

Portolettes

There will be port-a-potties on course. Please respect our community and utilize these for your needs.

Hydration

Water & Hydration Stations will be staggered approximately every 3-4 miles. Specific locations on map to come.

Nutrition

Precision Hydration, the Official Energy Gel of the 2025 Boulderthon, will be available at our pre-race fueling station before the race, and 3 additional stations on course. Please see maps for specific locations.
- Precision energy gels are practical and efficient way to get 30g of carbohydrate into your system fast. PF 30 Energy Gel have a mild, neutral "Original" flavor to reduce flavour fatigue during longer efforts. The texture is designed to reduce stickiness in the mouth and minimize the need to wash them down with fluid immediately.

Medical

A number of highly trained physicians, nurses, physical therapists and other medical personnel will be on hand throughout race weekend.
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.

Cheer runners on at the Finish! First 250 spectators will get cowbells. Join the fun at Spruce & 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 Xcel Power-Up Cheer Station information will be coming soon!
Our Official After Party will be at Avanti. Celebrate your incredible accomplishment with the best views in town at the Avanti roofdeck!

Miranda

"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."

Jess

"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."

Brad

"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!"

Matt

"Great Day, Great Race. I can’t imagine a marathon that is run any better. Everything went well, volunteers were plentiful and helpful, aid stations were great, and the weather was perfect for a long run. And Boulder turned out in force to cheer us on."

Pete

"Fantastic First. Terrific race, beautiful course. Staff and volunteers were first class all the way!"

Jamie

"This was my 1st half marathon race and I had a blast! Everyone was in a great mood and the course was beautiful! Thank you all!"

95% of runners would recommend to their friends, with #1 reason being Downtown Finish & Course Views.

Read reviews on Racecheck

HALF MARATHON

Boulderthon was ranked as one of the Top 5 Best Half Marathons in the U.S. by Active

Boulderthon Half Marathon

Boulderthon Half Marathon Registration

Event Day
Logistics

Boulderthon 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."

"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."

"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!"

HALF MARATHON

Boulderthon was ranked as one of the Top 5 Best Half Marathons in the U.S. by Active

Boulderthon Half Marathon

Boulderthon Half Marathon Registration

Event Day Logistics

Boulderthon 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."

"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."

"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!"

Event Day
Logistics