Seaville is an unincorporated community and census-designated place (CDP) located within Upper Township in Cape May County, in the U.S. state of New Jersey.

Upper Township is a large township in Cape May County, in the U.S. state of New Jersey. The township, and all of Cape May County, is part of the South Jersey region of the state and of the Ocean City metropolitan statistical area, which is part of the Philadelphia-Wilmington-Camden, PA-NJ-DE-MD combined statistical area, also known as the Delaware Valley or Philadelphia metropolitan area. As of the 2020 United States census, the township's population was 12,539, an increase of 166 (+1.3%) from the 2010 census count of 12,373, which in turn reflected an increase of 258 (+2.1%) from the 12,115 counted in the 2000 census.