Kauai County or Kauaʻi County (Hawaiian: Kalana o Kauaʻi), officially known as the County of Kauaʻi, is a county in the U.S. state of Hawaiʻi. It encompasses the islands of Kauaʻi, Niʻihau, Lehua, and Kaʻula. According to the 2020 Census, the population was 73,298. The county seat is Līhuʻe.
The Kapa'a Micropolitan Statistical Area includes all of Kauai County.
Niʻihau, sometimes written Niihau, is the seventh largest island in Hawaii and the westernmost of the main islands. It is 17.5 miles (28.2 km) southwest of Kauaʻi across the Kaulakahi Channel. Its area is 69.5 square miles (180 km). Several intermittent playa lakes provide wetland habitats for the Hawaiian coot, the Hawaiian 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 Niihau and the neighboring island and State Seabird Sanctuary of Lehua as Census Tract 410 of Kauaʻi County, Hawaii. Its 2010 census population was 170, most of them native Hawaiians. As of the 2020 census, the population had fallen to 84. The people of Niʻihau are noted for their gemlike lei pūpū (shell lei) craftsmanship. They speak Hawaiian as a primary language.
Elizabeth Sinclair purchased Niʻihau in 1864 for US$10,000 from the Kingdom of Hawaiʻi. The island's private ownership passed on to her descendants, the Robinsons.