Plainfield is a town in Windham County, Connecticut, United States. The population was 15,405 at the 2010 census. The town comprises four villages: Plainfield (south, ZIP code 06374), Moosup (northeast, 06354), Wauregan (northwest, 06387), and Central Village (west, 06332). Each village has their own respective United States Post Office and fire department. The entire town is serviced by the 860 area code.