Fredonia is a borough in central Mercer County, Pennsylvania, United States.

Based upon the success of his business and the further gains that could be made after the construction of a proposed railroad, Simmons purchased the land that became the borough of Fredonia and had it surveyed and divided into lots.

Fredonia was serviced by Bessemer and Lake Erie Railroad passenger trains between 1869 and 1955.

The Fredonia Volunteer Fire Department was established in 1934 and has continued to host their “Old Home Week” festival each summer since 1935.

[5] During the Depression, the borough applied for and received Works Progress Administration funds.

[5] The elementary school was closed by the district in the mid-1990s, and the building was subsequently purchased and converted into a personal care and independent living facility.

A brass placard denoting the spot is located on the premises of "Fredonia Stainless Exhaust", at the southwestern 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 land.