Weißensee (German for "white lake") is a town in the district of Sömmerda, in Thuringia, Germany.

Due to its excellent strategic position between two lakes – from which the town takes its name – and a ridge of hills, Weissensee rapidly became a very important trade centre, especially for fish and woad.

Some notable figures lived on the Runneburg and in 1446 William III, Landgrave of Thuringia adopted the first Thuringian constitution.

Weissensee is famous for its medieval castle, one of the largest in Thuringia, and for its annual Bierfest.

[citation needed] Since October 2017, there has been a private weather station in Weißensee, whose data measured at an altitude of 143 m above sea level are permanently available on the Internet.