Which lake system is the largest lake in Finland?

The largest lake system in Finland is Saimaa.

Saimaa lies in southeastern Finland and covers about 4,279 square kilometres, making it the country’s largest lake. It is not a simple, single-basin lake: a maze of connected basins, channels and islands forms the wider Saimaa system. Major sections include Orivesi, Puruvesi, Haukivesi, Pihlajavesi and Pyhäselkä.

The lake was shaped by glacial activity near the end of the last Ice Age. About 6,000 years ago, ancient Saimaa found a new outlet, dramatically changing the region’s drainage and landscape. Today, its waters leave through the Vuoksi River, which flows eastward into Lake Ladoga in Russia.

A common mix-up is choosing Päijänne or Inari, both major Finnish lakes. They are large, but neither matches Saimaa’s area. Saimaa is also famous for the endangered Saimaa ringed seal, which lives nowhere else in the wild. The Saimaa Canal links the lake to the Gulf of Finland.