Clark is a borough in western Mercer County, Pennsylvania, United States, along the southern shore of the Shenango River Reservoir.

The original community was moved to the present site following the construction of a Shenango River dam for flood control near Sharpsville.

As of the census[7] of 2000, there were 633 people, 227 households, and 194 families residing in the borough.

There were 233 housing units at an average density of 76.5 per square mile (29.5/km2).

11.9% of all households were made up of individuals, and 5.3% had someone living alone who was 65 years of age or older.