Kaihu is a locality and settlement in Northland, New Zealand. The Kaihu River runs through the Kaihu Valley into the Wairoa River near Dargaville, approximately 32 km south east. State Highway 12 runs along the valley and passes through Kaihu settlement. Aranga is about 10 km north west. The Kaihu Forest is to the east and the Marlborough Forest is to the north.
The local hapu are Te Roroa of the Ngāti Whātua iwi.