Welwyn Preserve County Park is a 204-acre (0.83 km2) public nature reserve in Glen Cove, on the North Shore of Long Island in the U.S. state of New York.
Welwyn Preserve was originally Welwyn Estate, the estate of the industrialist Harold I. Pratt. The main house, Welwyn, was one of the Gold Coast Mansions.
The Welwyn estate also includes woodland and other natural habitats, as well as part of the coast facing north onto Long Island Sound. The mansion is currently used as the Holocaust Memorial and Tolerance Center of Nassau County.