Sean O'Brien 100K
JAN
31
2026
Run the Sean O'Brien trail race in Calabasas on Jan 31, 2026 for scenic trails and rewarding climbs across multiple distances. Choose from 30K to 100K with the 100K as a Western States 100 qualifier; register by Dec 15.
Sat 31 Jan 2026
100 kilometers
50 miles
50 kilometers
26 miles
30 kilometers
Always double-check with the organizer's website! This page may contain affiliate links.
Event details
Sean O'Brien is a trail running event held Saturday, Jan 31, 2026, in Calabasas, California. The venue address is 1925 Las Virgenes Road. The event includes multiple race distances and is listed as a qualifier for the Western States 100 for the 100K distance.
Distances and registration
- 100K
- 50 Miler
- 50K
- 26.2 (marathon)
- 30K
Registration closes Monday, Dec 15 at 11:59 PM PT. Visit the organization's website for the most recent information.
100 km
100k
50 mi
50 Miler
50 km
50k
26 mi
26.2
30 km
30k
