The Whau River is an estuarial arm of the southwestern Waitemata Harbour (rather than a river) within the Auckland metropolitan area in New Zealand. It flows north for 5.7 kilometres (3.5 mi) from its origin at the confluence of the Avondale Stream and Whau Stream to its mouth between the Te Atatū peninsula and the long, thin Rosebank Peninsula in Avondale. It is 800 metres (2,600 ft) at its widest and 400 metres (1,300 ft) wide at its mouth. The Whau River is named after a native tree, the whau (Entelea arborescens).