Gordy Ainsleigh (born 1947) is an American ultrarunner and is a California based chiropractor and pioneer of the 100-mile (160 km) trail ultramarathon, a form of extreme long-distance trail running.
In 1974, Ainsleigh was the first to run the course of the Western States Endurance Run. At the time, the trail was used only by horses participating in the 24-hour Western States Trail Ride. When his horse went lame prior to the race, Ainsleigh decided he would run the torturous 100 miles (160 km) of mountain trail from the Squaw Valley Ski Resort to Auburn, California, rather than look for another horse to ride. Ainsleigh completed the 'equestrian race', without a horse, in 23 hours and 47 minutes. This was the beginning of The Western States Endurance Run , and the beginning of the modern sport of ultradistance trail running.
Ainsleigh has finished the Western States 100 twenty-two times, most recently in June, 2007, though he unofficially completed the race in just over 30 hours (the official cutoff) in 2010. His fastest time was 20:55, in 1984.
- Ainsleigh, Gordy. Inventing 100-Mile Trail Racing. Marathon & Beyond, June 1998.
- Ainsleigh, H. Gordon. The 100-Mile Trail Run—with a Few Adjustments. "Dynamic Chiropractic" 1996 (Retrieved March 11, 2006)
- Western States Endurance Run (1996). Western States Endurance Run information tri-fold. (Retrieved March 11, 2006)
- Ainsleigh, H. G.. "Beneficial Effects of Sun Exposure on Cancer Mortality". Preventive Medicine. 1993 Jan;22(1)132-40
- Ainsleigh, Gordy. "My 100-Mile Dash". Endurance Digest. Nov-Dec, 1974.
- Ainsleigh, Gordy. "Memories of Smoke". Western Horseman. January, 1978.