Fredonia is a borough in Mercer County, Pennsylvania, United States. The population was 652 at the 2000 census. It is part of the Youngstown–Warren–Boardman, OH-PA Metropolitan Statistical Area.
Fredonia is located at 41°19′17″N 80°15′31″W / 41.32139°N 80.25861°W / 41.32139; -80.25861 (41.321460, -80.258563).
Fredonia is also the proven geographic center of Mercer County, Pennsylvania. A brass placard denoting the spot is located on the premisis of "Fredonia Stainless Exhaust", at the southwest corner of Main and 1st Streets. According to the United States Census Bureau, the borough has a total area of 0.4 square miles (1.0 km²), all of it land.