Kaū is the southernmost district on the island of .
Kaū 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, , and Pāhala.
The district contains much of Hawaii Volcanoes National Park, including the volcanoes Kīlauea and Mauna Loa, and , Papakōlea (Green Sand) Beach and Kamilo Beach. To the east of Kaū is the Puna District, and to the west is the South Kona District.
Sugar cane was a large crop until 1996. Now coffee is growing in importance, with the Kaū Coffee Festival held in Pāhala.
The southernmost point of the US is at Ka Lae Point in the Kaū District. However, although Palmyra Atoll is an unorganized incorporated territory by the United States federal government and not part of a state within the US, the atoll is officially the most southern.