Linntown is a census-designated place (CDP) in East Buffalo Township, Union County, Pennsylvania, United States.

Named for the Linn family who owned several farms on the south side of the Lewisburg-Mifflinburg turnpike (present-day Route 45), it originally consisted of just a few houses on the north side of the turnpike.

Arrival of the railroad stimulated commercial ventures such as the Kulp Lumber Mill and the Lewisburg Chair Factory (1887, forerunner of Pennsylvania House).

Linntown saw large population growth when the Linn farms were developed into residential building lots in the 1920s.

According to the United States Census Bureau, the CDP has a total area of 0.7 square miles (1.8 km2), all land.