Muddy Run is a long 2nd order tributary to Georges Creek in Fayette County, Pennsylvania.
Muddy Run rises about 0.25 miles east of Oliphant Furnace, Pennsylvania, and then flows west and south to join Georges Creek at Fairchance, Pennsylvania.
Muddy Run drains of area, receives about 44.2 in/year of precipitation, has a wetness index of 410.02, and is about 36% forested.