Boulderthon Marathon
Where the 2027 race is now
- Registration openRegister for 2027
- Race daySunday, September 26, 2027
- ResultsPosted here as soon as the timer has them
- Race day
- Sep 26, 2027 Sunday
- Distance
- 26.2 mi Marathon
- Entry
- Open Open entry
- Live tracking
- Not yet Shown here race week
Quick facts
- Sells out every year, online entry only, with no race-day registration.
- Start and finish sit around 5,335 feet, and the altitude costs most visitors more than the terrain does.
- About 603 feet of climbing after a course rebuild, on 98 percent paved surfaces.
- Six-hour limit at 13:43 per mile, with the finish line closing at 2 p.m.
- USATF-certified Boston qualifier, course CO23008MWC.
Course
Runners leave downtown on Pearl, head out North 51st Street past Boulder Reservoir, and spend the middle third on the county back roads under the Flatirons that local pros use for training. The route then turns back toward town for a finish on the pedestrian Pearl Street Mall, which is a genuinely unusual last quarter mile for a road marathon. A course rebuild cut marathon climbing to about 603 feet from roughly 983, so what is left reads as rolling rather than hilly, and the profile is no longer the hard part. Surfaces are 98 percent paved road and paved multi-use path, with one short packed-gravel stretch.
Race-day weather
Late September mornings in Boulder often start near 40 degrees and warm fast under thin high-altitude sun, which is why the organizers push gear check hard. Temperature is not usually the problem. Air is. Start and finish sit around 5,335 feet and the course never drops below that, so a familiar pace costs more oxygen than it does at home and visiting flatlanders tend to pay for it in the last 10K whether or not the day stays cool.
About the Boulderthon Marathon
Growth has been the story here. The race has roughly doubled its field year over year since it started, sold out every edition, and now anchors the largest September running weekend in the country. That has consequences for planning: online entry is the only path, there is no race-morning signup, and waiting on a late decision usually means missing it. Deferrals and transfers exist for a fee, refunds do not. The full marathon is open to runners 13 and up.
Past Boulderthon Marathon dates and results
| Year | Date | Status | Results |
|---|---|---|---|
| 2027 | Sunday, September 26, 2027 | Upcoming | — |
| 2026 | Sunday, September 27, 2026 | Results available | Open results |
| 2025 | Sunday, September 28, 2025 | Results available | Open results |
| 2024 | Sunday, September 29, 2024 | Results available | Open results |
Your race experience
Ran the 2026 Boulderthon Marathon?
Share what helped you on race day: the course, transport, aid stations or finish area.
Boulderthon Marathon FAQ
When is the Boulderthon Marathon?
The 2027 Boulderthon Marathon is on Sunday, September 26, 2027.
Is registration open for the 2027 Boulderthon Marathon?
Registration for the 2027 Boulderthon Marathon is open. View the official registration details at boulderthon.org.
How do I track a runner in the Boulderthon Marathon?
Most races publish tracking in race week. Marathon Scout links the official tracker on this page during race week, once the race or its timing provider publishes it.
Where can I find the Boulderthon Marathon results?
The 2026 results and earlier years are linked on the Boulderthon Marathon results page.
Is Boulderthon Marathon a Boston qualifier?
Yes. Boulderthon Marathon is a Boston Marathon qualifier. To use the result, you must run the certified full-marathon course within the qualifying window and meet the current standard for your age and gender. Meeting the standard lets you apply but does not guarantee entry, and net-downhill courses can receive a time adjustment under current B.A.A. rules. Review the Boston qualifying times and downhill-course rules, or browse upcoming Boston qualifier marathons.
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