Keaau is a census-designated place (CDP) in the Puna District of Hawaii County, Hawaii, United States. The population was 2,010 at the 2000 census.
Keaau is located at 19°37′16″N 155°2′30″W / 19.62111°N 155.04167°W / 19.62111; -155.04167 (19.621072, -155.041706). According to the United States Census Bureau, the CDP has a total area of 2.5 square miles (6.4 km²), all of it land.
The Board on Geographic Names officially designated the populated place as Keaʻau in 2003.