lake in west-central Bolivia, occupying a shallow depression in the Altiplano, or high plateau, at 12,090 feet (3,686 metres) above sea level. It is the country's second largest lake and covers 977 square miles (2,530 square km) at low stage. It is about 56 miles (90 km) long and 20 miles (32 km) wide but only 8 to 10 feet (2.4 to 3 metres) deep.

The Desaguadero and Márquez rivers feed the lake, and its only visible outlet is the Lacajahuira River. During floods (high stage) it spills into the Coipasa Salt Flat, 50 miles (80 km) to the southwest. Salt content of the water is heavy because of excessive evaporation. Settlement on its shores, made marshy by filtration of water into the lake bed, is sparse. Flamingos inhabit the shores of the lake. Lake Poopó has been polluted by nearby mining operations.