25K run

The 25K run (25 kilometers, approximately 15.52 miles) is a long distance running footrace that is between the distance of a half marathon and a marathon. It was formerly an official world record distance in road running by World Athletics, but has since been downgraded to world best status. Separately, the Association of Road Racing Statisticians retains world records in the 25K distance. The ARRS holds different standards for records than World Athletics, with exclusions for certain point-to-point races and mixed sex races. As a result its women's world record is 1:26:34 by Nancy Conz, set in 1982.

The distance was more common in the mid-20th century as mass road running was beginning to develop, but began declining with the increased popularity and familiarity of the marathon and half marathon distance. Some former 25K races have transitioned to shorter distances, with which runners and sponsors are more familiar. In particular, the establishment of the World Athletics Half Marathon Championships in 1992 proved a driver for private races and national championships to switch to the half marathon as the most common distance between the 10K run and the marathon.

However, as trail running and ultra running continue to find larger participant fields, the 25K has become a more common trail race distance (many trail races and ultra races use the metric system). As runners prepare for a 100K run, they may do training race steps with a 25K followed by a 50K.