The Hardrock Hundred Mile Endurance Run is an ultramarathon of 102.5 miles in length, plus 33,197 feet of climb and 33,197 feet of descent for a total elevation change of 66,394 feet, at an average elevation of over 11,000 feet.

The run is held on a loop course on 4WD roads, dirt trails, and cross country in Southern Colorado’s San Juan Range, USA.

The run has been held in early July of each year beginning in 1992, except for 1995 (too much snow), 2002 (nearby forest fires), 2019 (too much snow), and 2020 (COVID-19 pandemic). Each year’s run is run opposite to the previous year’s event (2023 was run in the counter-clockwise direction; 2024 will be clockwise).

In order to complete the event, instead of crossing a finish line, runners are required to “kiss the Hardrock”, a picture of a ram’s head painted on a large block of stone mining debris.

This course offers a graduate level challenge for endurance runs. The course is designed to provide extreme challenges in altitude, steepness, and remoteness. Mountaineering, wilderness survival and wilderness navigation skills are as important in this event as your endurance.

The Hardrock 100 is the centrepiece of the “Rocky Mountain Slam“, which a runner completes if s/he finishes Hardrock plus three of four other races in the Rocky Mountains: Leadville Trail 100, the Bear 100 Mile Endurance Run, the Bighorn 100, or the Wasatch Front 100 Mile Endurance Run. The award is presented at and hosted by the Bear 100 Mile Endurance Run, as this is the final run in the series.

Kilian Jornet and Courtney Dewaulter currently hold Course Records.