Drużno

thumb|250px|Location of Druzno Lake Drużno or Drużno (, ) is a body of water historically considered a lake in northern Poland on the east side of the Vistula delta, near the city of Elbląg. As it is currently not deep enough to qualify as a lake hydrologically and receives some periodic inflow of sea water from the Vistula Lagoon along the Elbląg River, some suggest that it be termed an estuary reservoir. A village of recent origin also called Drużno is situated near the lake.

The German name Drausensee, in earlier records called Drusensee, is connected to the ancient trade city of Truso, which stood within the lands now occupied by Elbląg. The lake is greatly reduced from its original size partly due to large building expansion of housing in the last few decades, but mainly because of the natural death of the lake by sedimentation. The lake is the site of a nature reserve, one of the 13 sites in Poland protected under the Ramsar convention.