The Tamaki River, despite its name, is actually an estuarial arm of the Hauraki Gulf, close to the city of Auckland in New Zealand. It extends south for 15 kilometres from its mouth between the Auckland suburb of Saint Heliers and the long thin peninsula of Bucklands Beach, which reaches its end at Musick Point.

The river extends past the suburbs of Glendowie, Glen Innes, Tamaki, Panmure, and Otahuhu to the west, and Sunnyhills and Pakuranga to the east.

It has several smaller "tributary arms" which extend from it: the Pakuranga Creek and Otara Creek in the east, and the Otahuhu Creek and Panmure Basin in the west. The Otahuhu Creek forms the eastern shore of the narrowest point on the Auckland isthmus: here it is less than two kilometres to the waters of the Manukau Harbour, an arm of the Tasman Sea.