The Kaipara River drains the area to the northwest of Auckland, New Zealand.

It flows north from the northern foothills of the Waitākere Ranges, meandering past the town of Helensville.

It is joined by the Kaukapakapa River in its lower tidal reaches shortly before entering the southern Kaipara Harbour.

Other major tributaries are the Ararimu, Ahukuramu, Waimauku and Waipatukahu streams.

The area around the river was historically occupied by the Te Taoū hapu of Ngāti Whātua in the lower catchment near present-day Helensville, and by Te Kawerau ā Maki in the upper sections near Kumeū.