Kosaki (Biała Piska) , submerged village in the powiat Piski, Warmian-Masurian Voivodeship, Kossaken until 1938 , Wächtershausen from 1938 to 1945 , Johannisburg district, East Prussia
Kosaki (Piątnica) , village in the powiat Łomżyński, Podlaskie Voivodeship