The Los Reyunos Dam is an embankment dam on the Diamante River, in central Mendoza Province, Argentina, some twenty-two miles (thirty-five kilometers) from the city of San Rafael.

The dam, built of stone and compacted clay to minimize execution and cost, is 440 feet (130 meters) high and contains a reservoir covering an area of 1,828 acres (7.40 km2).

About one mile (two kilometer) downstream is a smaller, compensation dam, which forms the lower reservoir, called El Tigre.

The reservoir is employed in raising Salmonidae and silverside, allowing for sport fishing.

Los Reyunos Fishing and Nautical Club, along with private summer residences and a hotel, lies on the western shore of the reservoir and serves as a base for activities in the lake (such as windsurf, canoeing) and in the surrounding mountains (such as hiking).