Harmony is a borough in Butler County, Pennsylvania, United States. The population was 937 at the 2000 census. It is located about 30 miles north of Pittsburgh, Pennsylvania.
According to the United States Census Bureau, the borough has a total area of 0.4 square miles (1.0 km²), all of it land.
As of the census of 2000, there were 937 people, 409 households, and 267 families residing in the borough. The population density was 2,468.0 people per square mile (952.0/km²). There were 434 housing units at an average density of 1,143.1 per square mile (441.0/km²). The racial makeup of the borough was 99.15% White, 0.53% African American, 0.21% Native American, and 0.11% from two or more races. Hispanic or Latino of any race were 0.64% of the population.