Martins Fork is a 32-mile river in Bell and Harlan Counties in Kentucky in the United States. The river flows east and north from its source in the Cumberland Mountains, a subrange of the Appalachian

Harlan County is located in southeastern Kentucky. As of the 2020 census, the population was 26,831. The county seat is Harlan. Kentucky's highest natural point, Black Mountain, is in Harlan County.