Olsztyn is a city on the Łyna River in northern Poland. It is the capital of the Warmian-Masurian Voivodeship, and is a city with county rights. …Olsztyn is a city on the Łyna River in northern Poland. It is the capital of the Warmian-Masurian Voivodeship, and is a city with county rights. The population of the city was estimated at 169,793 residents in 2021.