Eighty Four is a census-designated place in Somerset, North Strabane, and South Strabane townships in Washington County, Pennsylvania, United States. It lies approximately 25 miles (40 km) southwest of Pittsburgh and is in the Pittsburgh metropolitan area. The population was 657 at the 2010 census.
Eighty Four contains the 84 Lumber company's headquarters. Eighty Four is a part of the Canon-McMillan, Trinity, Ringgold, and Bentworth school districts.
Eighty Four is accessible via Pennsylvania Route 519 and Route 136 and interstates 79 and 70. The closest international airport is the Pittsburgh International Airport approximately 25 miles northwest of Eighty Four in Findlay Township.
Eighty Four was originally named Smithville. Due to postal confusion with another town of the same name, its name was changed to "Eighty Four" on July 28, 1884. The origin of the name is uncertain.