Lake Bagsværd is a lake in northeastern Zealand, Denmark. After Furesø, it is the second largest lake in the Mølleå system. The lake is an appendix to the Mølleåen via Furå further on to Lyngby Lake.
The water quality in the lake is not suited for swimming as the lake still receives spillover from three outlets from the public sewer system. The sewer pollution is worsened by the fact that the water in the lake stays in the lake for several years. The lake receives very small amounts of clean water from the surrounding areas. Mostly because of very intensive fresh water pumping from nearby wells.
