Caumsett State Historic Park Preserve is a state park on Lloyd Neck, a peninsula extending into the Long Island Sound, in the Village of Lloyd Harbor, New York.^[6][7] It is operated by the New York State Office of Parks, Recreation and Historic Preservation.

The 1,520-acre (6.2 km²) park^[2] covers the former Marshall Field III estate that was developed in the 1920s, and was listed on the National Register of Historic Places in 1979. Much of the park is today managed as a nature preserve, with a focus on protecting high-quality bird habitat.