Hahnville is a census-designated place (CDP) in and the parish seat of St. Charles Parish, Louisiana, United States. The population was 2,792 at the 2000 census. For information on the origin of Hahnville, see Michael Hahn (1830–1886).
Hahnville is located at 29°58′1″N 90°24′36″W (29.967081, -90.410129).
According to the United States Census Bureau, the CDP has a total area of 8.8 square miles (23 km2), of which 7.8 square miles (20 km2) is land and 1.0 square mile (2.6 km2) (11.79%) is water.
As of the census of 2000, there were 2,792 people, 987 households, and 752 families residing in the CDP. The population density was 358.8 people per square mile (138.6/km2). There were 1,078 housing units at an average density of 138.5 per square mile (53.5/km2). The racial makeup of the CDP was 47.82% White, 50.90% African American, 0.29% Native American, 0.11% Asian, 0.21% from other races, and 0.68% from two or more races. Hispanic or Latino of any race were 1.15% of the population.
There were 987 households, out of which 39.1% had children under the age of 18 living with them, 49.2% were married couples living together, 22.1% had a female householder with no husband present, and 23.8% were non-families.