The Keep River is a 258 km long river located in the Victoria Bonaparte bioregion of Western Australia and the Northern Territory in Australia.
The river rises just south of the Newry Station homestead then flows in a northerly direction crossing the Victoria Highway and then flowing through the Keep River National Park and veering westward across the border into Western Australia then veering east back into the Northern Territory. It then continues north before discharging into the Joseph Bonaparte Gulf and the Timor Sea.
The river catchment occupies an area of 6,003 square kilometres and is wedged between the Ord River catchment to the west and the Victoria River catchment to the east. The river has a mean annual outflow of 500 gigalitres.
Important wetlands are found in the lower reaches of the river, forming suitable habitat for waterfowl breeding colonies and roosting sites for migratory shorebirds. Large areas of rice-grass floodplain grasslands are also found along the river.
The estuary formed at the river mouth is in near pristine condition. It occupies an area of 230 square kilometres of open water. It is tide dominated in nature with a tide dominated delta having multiple channels and is surrounded by an area of 55.5 square kilometres covered with mangroves.
Marine fauna found along the river include fish including freshwater sawfish, dwarf wawfish, ox-eye herring, bony bream, short-tail thryssa, several species of catfish such as Arius and Anodontiglanis dahli, freshwater longtom, species of rainbowfish, hardeyheads, species of glassfish, species of grunter, species of mullet, spotted archerfish, species of gudgeon, species of goby and baramundi.[
