Iso-Naakkima is a lake in Southern Savonia, Finland, about 10 km south of the town of Pieksämäki.

It is notable for having an eroded impact crater under the northwestern part of the lake.

Of the known craters older than a billion years old, it is also one of the smallest being only 3 km in diameter.

[3] At the time of the impact event, the continent of Baltica (modern northeastern Europe) was located near the equator.

The discovery was made in 1989 and therefore Iso-Naakkima is the fourth known impact structure in Finland.