Desert Lake, Lagoon in Lago Argentino Department, Argentina

Lago del Desierto is a rectangular lake 10 km long and about 1 km wide, lying in a glacial valley between the Martínez de Rozas Range to the east and the Southern Patagonian Ice Field to the west. Its outlet, the de las Vueltas River, flows south to Viedma Lake. The valley runs between Lake O'Higgins/San Martín and Monte Fitz Roy.

Chilean settlers arrived from 1921, and two years later Vicente Ovando Vargas discovered the lake; Ismael Sepúlveda, who named it, settled on the north shore in the 1930s. A border dispute over the 1881 treaty's demarcation climaxed on 6 November 1965, when Argentine Gendarmerie fought Chilean Carabineros at Puesto Arbilla and Lieutenant Hernán Merino was killed. On 21 October 1994 an arbitration tribunal awarded Argentina the 481 km² in dispute, confirmed on 13 October 1995.

The name differs by country: Argentines say Lago del Desierto, while Chileans keep Laguna del Desierto, the name used by the settlers who found the water in the 1920s. Father Alberto María de Agostini recorded Ismael Sepúlveda Rivas and his wife Sara Cárdenas Torres living on the north shore in the 1930s; Sepúlveda gave the lake its name. The lake now lies within the Reserva Provincial Lago del Desierto, created in 2005.

The southern shore is reached by dirt road from El Chaltén; from Chile, walk about 30 km from the Candelario Mancilla crossing through forest, with horses sometimes available for heavy loads. The northern end, Punta Norte, holds the Argentine border post on the El Chaltén–Villa O'Higgins route, covered by hiking and ferry transfers. Get your passport stamped when crossing, and note that photography and drone use are banned around the border post.

The lake sits near Monte Fitz Roy, where large Andean condors can be spotted soaring above the water and peaks. These enormous birds are among Earth's largest flying creatures and often ride the mountain winds in this area.