The Dry Fork is a 39.1-mile-long (62.9 km) tributary of the Black Fork of the Cheat River in the Allegheny Mountains of eastern West Virginia in the United States. Via the Black Fork, the Cheat, and the Monongahela and Ohio rivers, it is part of the watershed of the Mississippi River. The Dry Fork flows for much of its length in the Monongahela National Forest and drains mostly rural and forested areas. According to the Geographic Names Information System, it has also been known historically as Dry Run. The stream's name derives from the occurrence of underground passages through which portions of the stream flow, leaving a dry streambed on the surface at times during the year.