Mystic Island is an unincorporated community and census-designated place located within Little Egg Harbor Township, in Ocean County, in the U.S. state of New Jersey. As of the 2010 United States Census, the CDP's population was 8,493. Mystic Island is a large, mostly waterfront development originally planned as a resort community that started in the early 1960s as a waterfront community with vacation bungalows.