Rochester is a borough in central Beaver County, Pennsylvania, United States, at the confluence of the Beaver and Ohio rivers. Located 25 miles (40 km) northwest of Pittsburgh, it is part of the Pittsburgh metropolitan area. The population was 3,472 at the 2020 census.

Beaver County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 168,215. Its county seat is Beaver, and its largest city is Aliquippa. The county is part of the Greater Pittsburgh region of the state.