Seaside Park is a borough in Ocean County, in the U.S. state of New Jersey. It is part of the New Brunswick–Lakewood, NJ Metropolitan Division, which is part of the New York metropolitan area. As of the 2020 United States census, the borough's population was 1,436, a decrease of 143 (−9.1%) from the 2010 census count of 1,579, which in turn had reflected decline of 684 (−30.2%) from the 2,263 counted in the 2000 census. Seaside Park is situated on the Barnegat Peninsula, a long, narrow barrier peninsula that separates Barnegat Bay from the Atlantic Ocean.

Ocean County is a county located along the Jersey Shore in the south-central portion of the U.S. state of New Jersey, and the southernmost county in the New York metropolitan area. The county borders the Atlantic Ocean on the east and in terms of total area is the state's largest county. Its county seat is Toms River. The county is considered part of the Central Jersey region of the state, though it was not among the four counties explicitly listed as included in Central Jersey as part of legislation signed into law in 2023.