Hay Island is a small peninsula off Darien on Long Island Sound in Connecticut, connected to the mainland by a short road leading to Long Neck Point Road. Its north side faces Ziegler's Cove. The peninsula contains two structures, including the home of William Ziegler III, a founder of the Maritime Aquarium at Norwalk. The site is notable as a distinct coastal feature of the Darien shore and for its association with Ziegler and the development of the aquarium.