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Sean O'Brien 100K

Name: Sean O'Brien 100K
Start: 2027-01-30
End: 2027-01-30
Location: Calabasas

Calabasas, United States • 30 Jan 2027

Sean O'Brien 100K and related trail races

The event takes place on January 30, 2027 in Calabasas, CA at 1925 Las Virgenes Road. It is a series of trail races organized by Keira Henninger Events and offers multiple distance options for runners.

Distances offered include:

100K
50 Miler
50K
Marathon
30K

The 100K distance is listed as a 2026 WS100 qualifier. Registration for the event closes on Tuesday, December 1 at 11:59 PM PT. Entry fees are shown in a range from 152.60 to 323.00 USD. The organizer lists multiple pricing options for entries and indicates availability for those offers beginning in mid 2026.

The event is presented as an offline, in person trail race in Calabasas. Media and course view points are noted for various miles along the route. Practical details such as exact start times are provided by the organizer but are not included here. Visit the organization's website for the most recent information.

United States California Calabasas

Race information

Website Registration

100 km

100k

50 mi

50 Miler

50 km

50k

26 mi

Marathon

30 km

30k

Visit the organization's website for the most recent information.

Trail runs nearby

Saturday Jul 25

Aztlan XC Classic

Los Angeles

5 km

Aztlan XC Classic is a 5K event in Elysian Park, Los Angeles on July 25, 2026, with youth and adult race categories and differing registration options. Proceeds support the Aztlan Athletics Foundation's camps and scholarships.

Friday Jul 31

SoCal Summer 12K

Pasadena

6 km

12 km

An evening trail event in Pasadena's Lower Arroyo Park offering 6K and 12K routes with chip timing and aid stations. The finish includes tacos and drinks and runners receive a commemorative shirt and wooden medal.

Saturday Aug 1

Conquer the Overlook 5K

Culver City

Urban Trail

5 km

A 5K run or walk with a 282 step climb at Baldwin Hills Scenic Overlook in Culver City that benefits the Aztlan Athletics Foundation. Registration runs from 10/10/2025 to 12/31/2025 with a $45 fee.

Saturday Aug 1

Dick Fitzgerald 2-Mile Beach Run

Hermosa Beach

2 mi

A two-mile beach run in Hermosa Beach, California on August 1, 2026, organized by the Mira Costa Track and Cross Country teams. Registration runs April 17 to August 1 and the $30 fee supports the team.