Clarks Knob is a summit in Franklin County, Pennsylvania.

[3] It is the highest point on Blue Mountain, the eastern front range of Pennsylvania's Ridge and Valley Appalachians region.

[2] Clarks Knob's northeast-southwest running summit ridge forms the boundary of the Susquehanna River and Potomac River drainages.

[2] It stands over 1,600 feet (488 m) above the town of Chambersburg and the Great Appalachian Valley.

This mountain is protected within the Buchanan State Forest.