Wahiawā (Hawaiian pronunciation: [wəhijəˈvaː] ) is a census-designated place (CDP) 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 (also known as Wahiawā Reservoir or Kaukonahua). The town must be reached by either of two bridges on Kamehameha Highway (State Rte. 80) across the reservoir's narrow north and south arms. Outside of the reservoir, the town used to be surrounded by military bases and agricultural fields, but development is making its way up from the increasingly urbanized southern portion of the central plain. Still, there are significant U.S. Army facilities in the area, including Schofield Barracks, Wheeler Army Airfield, and East Range, an Army training area extending into the hills south and east of town. Schofield Barracks alone is larger than Wahiawā CDP. Wahiawā is also home to the United States Navy's Naval Computer and Telecommunications Area Master Station Pacific and the housing community HMR.

The U.S. postal codes for Wahiawā are 96786 and 96857.