Mamba 100 - Memphis, TN

Event overview

The Mamba 100 is a multi-distance trail event held at the Wolf River Refuge Trailhead on S. Walnut Bend Rd., Memphis, TN, on November 6-7, 2026. Distances offered are 100 miles, 100K, 50K, and 25K. Registration closes Monday, November 2 at 11:59 PM CT. The 100-mile race is an official Western States qualifying race; to earn the qualifier, runners must complete the full 100 miles within the 34-hour cutoff.

Course and distances

The course is centered on a roughly 14-mile loop of flat, fast, smooth single-track with a short lead-in section before entering the main loop. Loop and start-section breakdowns are approximately:

• 100 Miler - 7 loops + 2-mile start section
• 100K - 4 loops + 6-mile start section
• 50K - 2 loops + 3-mile start section
• 25K - 1 loop + 1.5-mile start section

Two fully staffed aid stations are on course: the Start/Finish at the trailhead and Walnut Grove Bridge, which is passed twice each loop. Aid stations provide water, electrolyte drink, soda, and standard ultra food. Drop bags are permitted at the Start/Finish aid station only.

Logistics, rules, and awards

Packet pickup is at the Wolf River Refuge Trailhead on the day before the race. No refunds and no bib transfers are allowed. Entry may be deferred for race credit at decreasing percentages depending on how far in advance the request is made. Age minimums are 18+ for the 100 Miler and 100K, 16+ for the 50K (parent/guardian waiver required), and 13+ for the 25K (parent/guardian waiver required).

Pacers are permitted for the 100 Miler and 100K only; no pacers for the 50K or 25K. Standard race rules apply: no muling, crew access limited to the Start/Finish area, no course cutting, and the event must be completed on foot. Top three male and female finishers in each distance receive awards. Finishers earn distance-specific buckles or medals for the 100-mile, 100K, 50K, and 25K events. Visit the organization's website for the most recent information.