Kajny [ˈkai̯nɨ] is a village in the administrative district of Gmina Jonkowo, within Olsztyn County, Warmian-Masurian Voivodeship, in northern Poland. It lies approximately 7 kilometres (4 mi) north-east of Jonkowo and 13 km (8 mi) north-west of the regional capital Olsztyn.

Before 1772 the area was part of Kingdom of Poland, and in 1772–1945 it belonged to Prussia and Germany (East Prussia).