Einfelder See is a lake in Schleswig-Holstein, Germany. At an elevation of 26.79 m, its surface area is 1.78 km². It is located in the northern suburb of Neumünster and in the Kreis Rendsburg-Eckernförde. The lake is located on a water divide of the rivers Stör and Eider. Most of the water originates from groundwater and precipitation, only a small portion reaches the lake from the adjacent Dosenmoor.