Lake Senftenberg (German: Senftenberger See, formerly called Speicherbecken Niemtsch—Niemtsch reservoir, Upper Sorbian: Złykomorowski jězor, Lower Sorbian: Złykomorowski jazor) is an artificial lake in Landkreis Oberspreewald-Lausitz, Brandenburg, Germany.

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.

The flooding rate was initially at up to 60 cubic metres per minute (2,100 cu ft/min).

[1] Since the commissioning of the first beach section in 1973, the lake has enjoyed great popularity as a recreational area with holidaymakers, bathers, surfers and sailors.

It created a marina with over 100 boat moorings, an 80-metre-long (260 ft) floating pier and a harbour building.