The record for the longest distance run on a treadmill was set in 2008 when Irishman Tony Mangan ran 251.79 miles on a treadmill over the course of 48 hours. This accomplishment, which was verified by Guinness World Records, is still undefeated as of February 2015.
Mangan, who was 51 years old when the record was set, is a professional ultrarunner. After retiring from competition, he ran an around-the-world race in support of a mental health charity in 2014. Mangan's personal bests include a 4 minute, 50 second mile; a 7 hour, 30 minute 50-mile run; and a 2 hour, 38 minute marathon.