Liepnitzsee, Natural lake in Wandlitz, Brandenburg, Germany.

Liepnitzsee is a lake in the Wandlitz lake district, eight kilometres north of Berlin's city boundary, on the land of Bernau bei Berlin and Wandlitz. It fills a forked glacial channel running across the Barnim ground-moraine plateau, its longest extent east to west, with end moraines up to 30 metres high around it. A wooded peninsula juts from the right shore, and the 34-hectare island Großer Werder lies in the lake.

The lake was formed during the last ice age when glacial movements carved a basin into the Brandenburg landscape. This glacial origin shaped the water body we see today.

The name Liepnitzsee likely derives from the Slavic word Lipna, meaning linden, suggesting linden trees once grew along the northern and eastern shores. On the 34-hectare island Großer Werder, a campsite established in the 1920s grew to over 250 pitches by 1990, run today by the Campingfreunde Liepnitzsee association with a maximum of 99 pitches.

A signposted hiking trail runs along the shore but is interrupted on the north side at a stretch of bank renaturalised around 1995. Cyclists can circle the lake on an asphalted forest path about 8 km long, passing through Ützdorf. The Großer Werder island is reached by a seasonal ferry with landing stages east and west of Ützdorf; there are no official bathing spots on the island, but any suitable bay can be used.

Großer Werder, the 34-hectare island, has belonged to the city of Berlin since 19 October 1914, when it was bought from Count von Redern for about 20,000 gold marks. A seasonal ferry links it to landing stages east and west of Ützdorf.