The Cinereous Harrier(Circus cinereus) is a South American bird of prey of the harrier family. Its breeding range extends from the Tierra del Fuego through Argentina and Chile to Bolivia, Paraguay and southern Brasil; and across the Andes north to Colombia.

The male's plumage is dark grey above with black wingtips and a white rump. The underparts are pale grey, with a rufous streaked belly. The female's plumage is brown above, with a white rump, and cream coloured underneath, with a streaked belly similar to the males. The female is larger than the male with an average size of 50 centimetres compared to the male's 40 centimetres.

This bird can be found in different open habitats, ranging from lowland marshes to the Andean Altiplano at a maximum altitude of 4500 metres. Like other harriers it nests on the ground. It is usually considered to be sedentary.

Its diet is variable, due to a wide range and variety of habitats. Its usual prey are small rodents and birds, reptiles, amphibians and insects.