Island Beach State Park is a New Jersey state park located just south of Seaside Park on the Barnegat Peninsula in Berkeley Township, Ocean County, New Jersey, United States. The park is operated and maintained by the New Jersey Division of Parks and Forestry. Most of the park encompasses the former borough of Island Beach. The park is the largest reserve of undeveloped barrier island in New Jersey and one of the largest in the United States. The park is divided into two areas.