Kaʻū is the southernmost and largest district (922 sq. miles or 2,388 km2) of Hawaii County, Hawaii, located on the island of Hawaiʻi.
Kaʻū was one of the six original districts of ancient Hawaii on the island, known as moku. It includes the areas of South Point (Ka Lae), Hawaiian Ocean View Estates (HOVE), Hawaiian Ocean View Ranchos (HOVR), now together known as Ocean View, Nīnole, Waiʻōhinu, Naʻālehu and Pāhala.
The district contains much of Hawaii Volcanoes National Park, including the volcanoes Kīlauea and Mauna Loa, and Punaluʻu Black Sand Beach, Papakōlea (Green Sand) Beach and Kamilo Beach. To the east of Kaʻū is the Puna District, and to the west is the South Kona District.
The southernmost point of any state in the United States is at Ka Lae Point in the Kaʻū District. It is almost the southernmost point in the whole country except that, technically, the United States Territory of Palmyra Island, although not part of a state within the US, is an incorporated territory (an integral part of the country) according to the doctrine of "incorporation" defined in the Supreme Court's Insular Cases; therefore Palmyra's south point on Holei Island at 5°52'15" N latitude is officially the southernmost point in the United States of America, not Ka Lae Point.