Fagnano Lake (Spanish: Lago Fagnano), also called Lake Cami (Spanish: Lago Cami), is a lake located on the main island of the Tierra del Fuego archipelago, and shared by Argentina and Chile. The 645 km² lake runs east–west for about 98 kilometres, of which 72.5 km (606 km²) belong to the Argentine Tierra del Fuego Province, and only 13.5 km (39 km²) to the Chilean Magallanes y la Antártica Chilena Region. It has a maximum depth of 449 meters. The southern bank is steep compared to the northern one, and expands in a considerably wide and flat piedmont from which both levels of the plateaus can be appreciated. From its western end, the Azopardo River drains towards the Almirantazgo Fjord. On its eastern end is the town of Tolhuin. The lake is located in a pull-apart basin developed along the Magallanes–Fagnano Fault zone.

According to a Selkʼnam myth, the lake was created alongside the Strait of Magellan and Beagle Channel in places where slingshots fell on earth during Taiyín's fight with a witch who was said to have "retained the waters and the foods".