Masontown is a borough in Fayette County, Pennsylvania, United States. It is part of the Pittsburgh Metro Area. The population of the borough was 3,450 at the 2010 census. It is served by the Albert Gallatin Area School District. Masontown is a small crossroads for the rural portions of western Fayette County, and it contains a small shopping center and a grocery store within its business district.
Fort Mason was built as a blockhouse from 1774 to 1778 by John Mason, also known as Johannes Phillip Maurer (1730-1812). Masontown became a town in 1798. He later moved to Ohio and is buried on a family farm in Columbiana County.
Masontown is located in southwestern Fayette County at 39°50′46″N 79°54′13″W (39.846228, -79.903492). The borough's western border is the Monongahela River, which forms the Washington County line, but the main settled part of the borough is 1 mile (1.6 km) east of and 200 feet (60 m) higher than the river.