Furnace Run is a long 2nd order tributary to the Youghiogheny River in Fayette County, Pennsylvania.
Furance Run rises in Buena Vista, Pennsylvania, and then flows northeast to join the Youghiogheny River about 1 mile west of Dawson.
Furnace Run drains of area, receives about 43.0 in/year of precipitation, has a wetness index of 348.92, and is about 67% forested.
Furnace Run is the location of Furnace Run Confluence BDA, which contains a scour area and a mature riverine forest as well as a rare plant species.