The Oreti River is one of the main rivers of Southland, New Zealand, and is 170 kilometres (110 mi) long. The river has been identified as an Important Bird Area by BirdLife International because, for much of its length, it supports breeding colonies of black-billed gulls.
The Oreti has its headwaters close to the Mavora Lakes between Lake Te Anau and Lake Wakatipu, and flows south across the Southland Plains to its outflow into Foveaux Strait at the southeastern end of Oreti Beach. En route, it runs through the towns of Lumsden and Winton, before passing through the city of Invercargill, close to the river's estuary.
For the final part of the river's length, around the city of Invercargill and the river's estuary just south of the city, it is known as the New River, a name occasionally encountered to refer to the whole river. It shares this estuary with several smaller rivers, most notably the Waihopai River.
The Invercargill Rowing Club relocated to the river in 1958.
Coordinates: 46°28′S 168°17′E / 46.467°S 168.283°E