Walpack Township is a township in Sussex County, New Jersey, United States. As of the 2010 United States Census, the township had a population of 16, reflecting a decline of 25 (-61.0%) from the 41 counted in the 2000 Census, which had in turn declined by 26 (-38.8%) from the 67 counted in the 1990 Census. Walpack Township was one of only four municipalities in New Jersey with a double-digit population as of the 2010 Census, and it placed third behind Tavistock (population 5) and Pine Valley (population 12), both in Camden County.