Harmonsburg is a census-designated place (CDP) in Crawford County, Pennsylvania, United States.

An early log grist and sawmill were located about a half a mile south of the village.

Harmonsburg is located in western Crawford County at 41°39′40″N 80°18′58″W / 41.66111°N 80.31611°W / 41.66111; -80.31611 (41.661068, -80.316181),[5] slightly east of the center of Summit Township.

Pennsylvania Route 18 passes through the community, leading north 7 miles (11 km) to Conneautville and south 5 miles (8 km) to the borough of Conneaut Lake at the southern end of the lake.

A great variety of timber—hemlock, sugar maple, pine, oak, sycamore, beech—are native here.

[4] According to the United States Census Bureau, the CDP has a total area of 1.4 square miles (3.6 km2), all land.