Wahiawa is a census-designated place in Honolulu County, Hawaii, United States, on the island of Oahu. It is in the Wahiawā District, on the plateau or "central valley" between the two volcanic mountains that bookend the island. In Hawaiian, wahi a wā means "place of the wa people". The population was 18,658 at the 2020 census. Lakes and reservoirs are rare in Hawaii, and Wahiawā is unique in being surrounded on three sides by Lake Wilson.