Orrstown is a borough in Franklin County, Pennsylvania, United States.

It is surrounded by Southampton Township in Franklin County, on the old state road from Shippensburg to Upper Strasburg.

It was incorporated as a borough on May 3, 1847, and in 1878 the town had one hotel, two stores, one carriage factory, and four churches: Lutheran, Presbyterian, United Brethren and Winebrennerian.

Chambersburg, the county seat, is 11 miles (18 km) to the south via PA 433 and U.S. Route 11.

According to the United States Census Bureau, the borough has a total area of 0.06 square miles (0.16 km2), all land.

[7] The borough sits on a low ridge between Conodoguinet Creek to the north and its tributary, Muddy Run to the south.