How to Register for the 2027 San Diego 100

Registration for the 2027 San Diego 100 opens January 1 at 12:01 AM and is first-come, first-served. You register through the Ultrasignup link posted on sandiego100.com, and you must meet the qualification requirement before you can enter. The race itself starts Friday, April 30, 2027, at 0600 in the Mt Laguna Recreational Area.

Key dates and facts

Step 1: Confirm you meet the qualification requirement

Before registering, check that you qualify. The site states applicants must have completed an official 50-mile race in 13 hours (the excerpt cuts off at "13 h," so confirm the exact cutoff and any additional conditions in the 2027 Racebook when it is posted).

If you don't yet have a qualifying 50-miler on record, you cannot enter the 2027 event until you do.

Step 2: Register through Ultrasignup

Registration is handled on Ultrasignup, not on sandiego100.com directly. The site points to an Ultrasignup registration link for the race. Because entry is first-come, first-served, plan to be at your computer at 12:01 AM on January 1 — popular 100-mile races can fill quickly, and there is no lottery for general entry.

Step 3: Check whether you qualify for a discount or free entry

Two options can reduce or eliminate your entry cost:

• Active military and first responders: a 10% discount is available. Email [email protected] to request a discount code. The site notes the discount is only for those who genuinely qualify.
• Scotty Mills Scholarships: up to 2 free entries are awarded to people who best demonstrate Scott Mills' trait of giving back to their community. To apply, prepare a 2–3 paragraph write-up explaining why you or someone else deserves a free entry and email it to [email protected] no later than December 28.

Step 4: Note the over-60 early start (if it applies to you)

Runners over 60 may start one hour early. However, aid stations open at their usual times, so if you take the early start, be prepared to self-support until the Cuyamaca Peak aid station. More details will be in the 2027 Racebook.

If you're aiming for Western States

The 2026 San Diego 100 is a qualifying race for the 2027 Western States 100. Runners who finish within 32 hours qualify to enter the Western States lottery. The qualifying period for 2027 Western States runs November 4, 2025, through November 2, 2026; the lottery is December 6, 2026, and that race is June 26–27, 2027. Note this applies to the 2026 SD100 — check the current Racebook for how the 2027 SD100 factors into future qualifying.

Common snags

• Trying to register on the wrong site. Registration goes through Ultrasignup; sandiego100.com only links to it.
• Missing the qualification cutoff. Verify your 50-mile finish time against the requirement before January 1.
• Waiting to register. There is no lottery for general entry — it's first-come, first-served, so late attempts may find the race full.
• Assuming the discount is automatic. Both the military/first responder discount and the scholarship require an email request, and the scholarship has a December 28 deadline.

For anything unclear, contact [email protected].