Río Negro, provincia (province), south-central Argentina. It lies within the region of Patagonia and extends westward from the Atlantic Ocean to the Andes Mountains and the border with Neuquén province. Viedma, in the east, is the provincial capital.

The province is crossed (northwest to southeast) by the Negro River. South of the Negro, most of the land consists of arid tablelands. To the west are the chains of lakes and the forested valleys of the Andes, the site of Nahuel Huapí National Park. The Atlantic coastline has one deep indentation, the Gulf of San Matías, in the northern bend of which is the small port of San Antonio Oeste.

The area was settled in 1782 by the explorer Basilio Villarino and was made a national territory in 1884. It became a province in 1955. A dam, built on the Negro River near Neuquén, made possible the irrigation of a large area between the Colorado (the province’s northern boundary) and Negro rivers, where alfalfa is grown, pears and apples are produced for export, and sheep are raised. The Sierra Grande mining and industrial complex was developed during the 1970s. Viedma is located near the mouth of the Negro River and on the railway that runs inland from San Antonio Oeste to San Carlos de Bariloche, a resort on the shore of Lake Nahuel Huapí. Area 78,384 square miles (203,013 square km). Pop. (2001) 552,822; (2010) 638,645.