• Top 10 in America USA Today 2024, 2025, 2026
  • #2 Fastest Growing Race in US - RunSignUp
  • Best Fall Marathons - Runners Wolrd
  • Top 10 in America USA Today
  • #2 Fastest Growing Race in US - RunSignUp
  • Best Fall Marathons - Runners Wolrd
  • Top 10 in America USA Today
  • #2 Fastest Growing Race in US - RunSignUp
  • Best Fall Marathons - Runners Wolrd
  • Top 10 in America USA Today
  • #2 Fastest Growing Race in US - RunSignUp
  • Best Fall Marathons - Runners Wolrd
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HALF MARATHON

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THE HALF MARATHON
WORTH RUNNING

Boulderthon Half Marathon

Date: Sunday, September 27th 2026

Start Time: 7:00AM

Half Marathon Pacing Groups

1:30, 1:45, 2:00, 2:15, 2:30, 2:40

Pacing provided by BEAST Pacing

Boulderthon was named among the Best Fall Marathons by Runner’s World, the Best Half Marathon in Colorado, and one of the Top 13 Most Beautiful Half Marathons in the World. Now in its sixth year, Boulderthon welcomes over 15,000 runners from all 50 states and 22 countries. Join us on Sunday, September 27, 2026, for the largest September running weekend in the U.S. in beautiful Boulder, Colorado.

BOULDERTHON HALF MARATHON REGISTRATION

Registration for the Boulderthon Half Marathon is now open.

REGISTER