San Diego 100

Event overview

The San Diego 100 is a 100-mile loop ultramarathon held in the Lake Cuyamaca area of San Diego County on May 1-2, 2026. The course is approximately 90% single-track mountain trail and includes sections of the Pacific Crest Trail, Noble Canyon, Cuyamaca and Anza Borrego State Parks, and the Mt. Laguna recreational area. The route lists about 15,400 feet of climbing and the same amount of descent and has a 32-hour time limit. The race serves as a qualifier for Western States 100.

Location and format

The start and finish area is at the south parking of Lake Cuyamaca Recreation Area, located on State Highway 79, about 9 miles southwest of Julian, CA. The event is a loop course that traverses multiple recreation areas and technical mountain terrain in hot and dry conditions.

Entry, divisions and requirements

Registration opens January 1, 2026 and will remain open until the race reaches 300 entrants on a first-come, first-served basis or until April 15, 2026. Applicant qualification requires completion of a 50-mile race in under 13 hours between January 1, 2023 and May 1, 2025, or completion of an applicable 100K or 100-mile race in that same period. Entrants must also complete six hours of trail maintenance or volunteer service between June 1, 2024 and May 15, 2025, or donate $100 to Trailfit. The event includes a Solo division with support restrictions, a small entry discount for Solo runners, a 10% discount for active military and first responders, and up to two free entries awarded via a scholarship application. Visit the organization's website for the most recent information.