Rockcastle County is a county located in the southeastern part of the U.S. state of Kentucky. Its county seat is Mt. Vernon. The county was founded in 1810 and named for the Rockcastle River, which runs through it. The river, in turn, is named for its majestic rock cliffs.

Area: 318 mi²

Founded: 1810

Population: 16,115 (2021)

County seat: Mount Vernon

Cities: Mount Vernon, Brodhead, Livingston