Sean O'Brien Trail Runs

The Sean O'Brien Trail Runs is an annual Southern California ultra-marathon and trail running event organized by KH Races (Keira Henninger Events). Named after the ultra-running course created following the Ray Miller fire, the event traverses the rugged single-track and fire roads of the Backbone Trail in the Santa Monica Mountains.

The 100k is a 2027 WS100 qualifier.

Distances being offered are 100k, 50 mile, 50k, Marathon, and 30k.

Let's kick off 2027 with an epic race through the Santa Monica Mountains! Thirteen years running and Sean O'Brien still brings some of the best and most challenging trail running in Southern California. We can't wait to have you all on the trails to celebrate with a great day of running.