Koszajny is a village in the administrative district of Gmina Małdyty, within Ostróda County, Warmian-Masurian Voivodeship, in northern Poland. It lies approximately 11 km west of Małdyty, 37 km north-west of Ostróda, and 63 km west of the regional capital Olsztyn. In November 1831, several Polish infantry units of the November Uprising stopped in the village on the way to their internment places.