Ansonia is a city in New Haven County, Connecticut, United States, on the Naugatuck River, immediately north of Derby, and about 12 miles (19 km) northwest of New Haven. The population was 18,531 at the 2010 census. The ZIP code for Ansonia is 06401. The city is serviced by the Metro North railroad. Ansonia Station is a stop on the railroad passenger commuter service's Waterbury line, connecting to New York's Grand Central Terminal.