Hannastown is an unincorporated community and important historical and archaeological site located in Hempfield Township, Westmoreland County, Pennsylvania, United States.

The village was founded in 1773 as the seat of the newly created Westmoreland County and was known as "Hanna's Town".

It was located along Forbes Road, the main route into the Ohio Country from eastern Pennsylvania, and named for Robert Hanna, an early settler whose tavern also served as Westmoreland County's first courthouse.

The village was rebuilt, but after Forbes Road was rerouted through Greensburg, the settlement grew little, and eventually, most of it became farmland.

Currently, the Historic Hanna's Town site includes the reconstructed Hanna Tavern/Courthouse, three vintage late 18th-century log houses, a reconstruction of the Revolutionary-era fort and blockhouse, a blacksmith shop, and a wagon shed housing an authentic late 18th century Conestoga wagon.