Sommen, Freshwater lake between Östergötland and Småland, Sweden

Lake Sommen is a freshwater lake on the border of Östergötland and Småland, about 147 metres above sea level. It covers 132 square kilometres, reaches a maximum depth of 60 metres, and has clear water with visibility of 8 to 10 metres. Its shoreline is mostly coniferous forest, with around 260 islands, the largest being Torpön.

During the 16th century, a Danish military force used the frozen surface of this lake to retreat and later reach a nearby town. This crossing played a role in regional military movements of that era.

The lake's traditional rowing boats, sommaskep, have a longer stem than other Swedish wooden boats, which helps in Sommen's short, steep waves. Torpa local history society had carpenter Gunnar Gustavsson build a copy of an antique sommaskep in Malexander in the early 1990s; new ones were built there in 2007 and 2016.

The northern end of Torpön island holds Naturum Sommen, the visitor centre and natural history museum, near the lake's central part. The surrounding area is sparsely populated, with Tranås, Malexander and Sommen as the main settlements. The climate is drier than much of southern Sweden, with February and March the driest months.

The Urkon legend continues beyond the lake's creation: the wizard Somme of Tullerum is said to have locked the cow in Urkons Grotta, where she rests on a bed of coal and fur. Each Christmas she eats one straw of the fur, and when none remain she will bring about the end of the world. Two raised stones at Fruhammar mark where she supposedly killed King Frode.