Långhalsen is a lake predominantly in

Nyköping Municipality Nyköping Municipality () is a municipalities of Sweden, municipality in Södermanland County in southeast Sweden. Its seat is located in the city status in Sweden, city of Nyköping, which is containing a majority of the residents. Its southern t ...

Södermanland Södermanland ( ), locally Sörmland, sometimes referred to under its Latinisation of names, Latinized form Sudermannia or Sudermania, is a Provinces of Sweden, historical province (or ) on the south eastern coast of Sweden. It borders Österg� ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

that is part of the

Nyköpingsån Nyköpingsån is a river primarily flowing through Södermanland County in Sweden. The river is named after Nyköping, where it flows into the Baltic Sea. Nyköping is also the largest settlement on the river proper and a large part of the drainage ...

drainage area A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, th ...

. There is a very small portion of the lake's northern inlet that is part of

Flen Municipality Flen Municipality () is a municipality in central Södermanland County in southeast Sweden. Its seat is located in the city of Flen. The present municipality was formed in 1971 through the amalgamation of the ''City of Flen'' (instituted in 194 ...

. There are three nearby lakes directly connected to its north that also are named Långhalsen due to their similar shapes, although they are considered separate lakes due to being connected by narrow rivers and straits. The lake surface is located at above sea level with multiple inlets and has several islands, the highest of which rises to .

References

Lakes of Södermanland County {{Södermanland-geo-stub