For trail running enthusiasts, the Colossal Vail 50/50 2026 presents an irresistible opportunity to challenge yourself amidst the stunning desert landscapes of southern Arizona. Set for the first week of December and organized by Fleet Feet Tucson and the Arizona Trail Association, this race takes place in Colossal Cave Mountain Park, about 24 miles southeast of Tucson, and offers some of the finest high desert trail running experiences available in the Southwest. The event is a key part of the Arizona Triple 50, alongside two other iconic races, making it a bucket-list adventure for ultrarunners. Strambecco rates the Colossal Vail 50/50 2026 as one of the Best Trail Running Race Events in the Southwest and one of the Best Trail Running Race Events in Arizona.

Whether you’re gearing up for the 50-mile ultra, the 55K (34 miles), or the long half marathon, each course follows portions of the Arizona Trail, weaving through breathtaking high desert terrain, canyons, and rolling hills. With gentle terrain, an expertly designed course, and expansive views of the Santa Rita Mountains, it’s no wonder this event has been a hit since its debut in 2014.

The Colossal Vail 50/50 offers three race distances: a 50-mile, 55K, and two variations of the half marathon (day and night). All races follow an out-and-back course format, starting and finishing at La Posta Quemada Ranch within Colossal Cave Mountain Park. The scenery transitions from desert cacti and yuccas to riparian zones as you move across different parts of the Arizona Trail.

The 50-mile course features a total elevation gain of approximately 4,000 feet as runners traverse the Arizona Trail through parts of Passages 7 & 8, passing through scenic riparian areas, open deserts, and rugged canyons. Starting from Colossal Cave Mountain Park, runners will head south, crossing Cienega Creek, navigating limestone formations, and passing under two tunnels beneath I-10 and Highway 83. The route offers sweeping views of the Santa Rita Mountains, with the high point at 4,200 feet reached after a steady climb.

The 55K course, measuring approximately 34 miles, shares much of the same route as the 50-mile course but has a slightly lower total elevation gain of around 3,000 feet. The course is designed to be fast, making it a great option for runners looking to push their endurance limits on a relatively runnable trail with fewer technical sections.

For runners who prefer shorter distances, the half-marathon options offer two distinct experiences: a 13.6-mile daytime-half marathon and a 13.1-mile nighttime version. The terrain is relatively flat, making these races accessible yet still challenging, with stunning desert vistas along the way. The nighttime version allows runners to enjoy the desert landscape under the stars.

The Colossal Vail 50/50 has a field limit of 300 participants across all distances, and spots fill up quickly so early registration is highly recommended. The 50-mile and 55K races both begin at 6:30 AM, while the half marathon starts at 8:00 AM. The nighttime half marathon starts at 6:00 PM. Aid stations are located approximately every 4-6 miles, stocked with essentials such as chips, pretzels, cookies, boiled potatoes, peanut butter and jelly sandwiches, and Tailwind Nutrition. Completion cutoff times are generous, with the 50-mile race allowing 14 hours, the 55K allowing 11 hours, and the half marathon offering plenty of time for participants to finish.