The Lanker See is a lake in the region of Holstein Switzerland in North Germany.

Almost the entire western area from the lakeshore to the tracks of the Preetz-Ascheberg railway line are a nature reserve.

The Lanker See has a surface area of 323.6 hectares (1.249 sq mi), is up to 21 metres deep and is about 19 m above sea level (NN).

It is divided into a large northern and a smaller southern part, that are joined by a passage a little more than 1 metre deep.

The Lanker See lies in the borough of Preetz and the municipalities of Kühren, Wahlstorf and Schellhorn.