Niʻihau or Niihau (/ˈniːhaʊ/; Hawaiian: [ˈniʔiˈhɔu]) is the westernmost and seventh largest of the inhabited Hawaiian Islands in the U.S. state of Hawaiʻi, lying 17.5 miles (15.2 nmi; 28.2 km) southwest of Kauaʻi across the Kaulakahi Channel and having an area of 69.5 square miles (180 km²). Several intermittent playa lakes provide wetland habitats for the Hawaiian Coot, the Black-winged Stilt, and the Hawaiian Duck. The island is designated as critical habitat for Brighamia insignis, an endemic and endangered species of Hawaiian lobelioid. The United States Census Bureau defines Niʻihau and the neighboring island and State Seabird Sanctuary of Lehua as Census Tract 410 of Kauai County, Hawaii.