Jamestown is a borough in Mercer County, Pennsylvania, along the Shenango River. The population was 636 at the 2000 census. It is part of the Youngstown–Warren–Boardman, OH-PA Metropolitan Statistical Area.
The town was founded in 1798 by James Campbell. The borough was incorporated in 1853.
The Jamestown area is served by the Jamestown Area School District, and is home to Combined Systems Inc, a tactical weapons producer that exports tear gas and smoke grenades.