Finland contains approximately 190 000 lakes or ponds. 

This relatively high number of lakes is caused by the temperate and wet northern climate, as well as by the qualities of the Finnish soil and bedrock. 

Unified bedrock and dense soils prevent water from sinking down into the ground. As a result, most of the water will remain in depressions and valleys above the ground.

Lakes can form in fissure valleys, as is the case with Lake Päijänne, or in depressions, such as the case of Inarinjärvi.

The oldest Finnish lakes have formed in craters that have been created by meteorites that have crashed down on Earth. Such crater lakes include Lappajärvi and Sääksjärvi. The Ice Age also caused the formation of various pools and depressions in which lakes have subsequently formed. 

The youngest Finnish lakes include the lakes that have formed as a result of post-glacial rebound in shore areas, as well as artificial lakes that have been built for electricity production, such as the Northern Finnish lakes Lokka and Porttipahta.

Most Finnish lakes are shallow, contain only little water and have gentle banks. The water of most Finnish lakes has been colored by soil types such as clay or humus.

The average depth of Finnish lakes is only seven meters. The deepest Finnish lakes are Päijänne (95 m) and Inarinjärvi (92 m).