The Rio Colorado Ultra Slam™ is a journey that tracks the spectacular geographical transformation of Texas. Runners trace the lifeblood of the Lone Star State, moving from the rugged granite cliffs of the Hill Country, winding through the sandy loam of the Lost Pines savannah, and culminating in a brutal, beautiful endurance showdown on the edge of the Gulf of Mexico.

From Tow, near the Canyon of the Eagles on Lake Buchanan to the Colorado River's mouth at Matagorda Bay, the river carves a path of approximately 431 to 432 river miles. The Ultra Slam challenges you to conquer this epic expanse on foot, anchored by our pinnacle achievement: a clean, rounded challenge distance of 400 MILES IN ONE YEAR.

Three Ways to Earn It

Note: Backyard ultras count toward the Ultra Slam 200 and 400 tiers only, when you reach the required distance (50+ miles for the 200, 100+ miles for the 400). Backyard ultras do not count toward the Ultra Slam 150, which requires five completed 50K trail races.

Qualifying Races

Choose your required number of races from the following, to be completed within the 2027 calendar year:

Entry Fee and Early Bird Pricing

Your Ultra Slam entry is a single bundled fee that covers all your chosen races. Register early to take advantage of our Founding Athlete Early Bird rates.

Payment plans are available at checkout: three monthly installments for any tier. Race swaps are permitted up to 60 days before the event date of the race you are dropping, subject to availability.

What You Get

• Entry into all your chosen races
• Custom Rio Colorado Ultra Slam finisher buckle
• Series jacket with tier designation
• Ultra Slam bib number carried across all events
• Your name on the permanent Rio Colorado Ultra Slam finisher wall

How It Works

1. Register here and pay the bundled entry fee for your tier.
2. Select your races at checkout (you can adjust up to 60 days before each race).
3. Show up. Finish. Repeat.
4. Receive your finisher buckle upon completion of your tier.

We track your qualifying finishes automatically, and you will receive a confirmation email after each race showing your progress.

Fine Print

• The 2027 season runs January 1 through December 31, 2027.
• All races must be completed within the 2027 calendar year.
• Backyard ultras must reach the qualifying distance (50 miles for the 200 tier, 100 miles for the 400 tier) to count. Backyard ultras do not count toward the Ultra Slam 150.
• Refunds are not available once the roster closes. Deferrals may be granted for documented medical reasons at the race director's discretion.
• Entrants who do not complete the required races receive credit toward individual race finishes but do not earn the Slam buckle or jacket.