Mascardi Lake, Glacial lake in Río Negro Province, Argentina

Mascardi Lake is a glacial lake in Nahuel Huapi National Park, Río Negro Province, Argentina, near Bariloche. It is V-shaped, with two arms of roughly equal length and width: the Catedral arm running north-south and the Tronador arm east-west. It reaches a maximum depth of 218 m and covers 39.2 km², with mountains rising steeply from the shore to over 1,800 m.

The lake is named after Nicolás Mascardi, a Jesuit missionary who worked in Patagonia during the 17th century. Before his arrival, indigenous groups had lived along its shores for a very long time, well before any European presence in the region.

The lake's name honours Nicolás Mascardi, a 17th-century Jesuit missionary who founded a mission on the shores of neighbouring Nahuel Huapi. Mapuche people were the main occupants of this area from the 17th until the late 19th century, and one campground on the northernmost part of the Catedral arm is still owned by a Mapuche community.

The lake is accessible via National Route 40, which passes near Villa Mascardi on the southern shore, where lodging and starting points for activities are available. Weather in Patagonia can change quickly, so visiting in late spring or early summer tends to offer more stable conditions for exploring the area.

The gravel plain separating Mascardi Lake from Lake Gutiérrez lies on the continental divide: Mascardi drains to the Pacific, Gutiérrez to the Atlantic. The two lakes sit side by side, yet their waters end in different oceans. The divide is crossed by the unpaved Route 82 along the western arm toward Ventisquero Negro.