Penn is a borough in Westmoreland County, Pennsylvania, United States. The population was 475 at the 2010 census. The borough was named for Pennsylvania founder William Penn.
Penn is located at 40°19′44″N 79°38′25″W (40.329018, -79.640141).
According to the United States Census Bureau, the borough has a total area of 0.2 square miles (0.52 km2), all of it land.
At the 2000 census there were 460 people, 182 households, and 133 families living in the borough. The population density was 2,974.7 people per square mile (1,184.0/km²). There were 187 housing units at an average density of 1,209.3 per square mile (481.3/km²). The racial makeup of the borough was 96.52% White, 1.52% African American, 1.09% from other races, and 0.87% from two or more races. Of the 182 households 37.4% had children under the age of 18 living with them, 51.1% were married couples living together, 18.7% had a female householder with no husband present, and 26.4% were non-families. 25.8% of households were one person and 12.6% were one person aged 65 or older. The average household size was 2.52 and the average family size was 2.99.