Lake Senftenberg (German: Senftenberger See, formerly called Speicherbecken Niemtsch—Niemtsch reservoir) is an artificial lake in Landkreis Oberspreewald-Lausitz, Brandenburg, Germany. It is located in the Lusatian Lake District, a chain of artificial lakes. The lake is located on the border of Lower and Upper Lusatia between the southern Brandenburg city of Senftenberg and its districts Niemtsch and Großkoschen.