Olsztyn (formerly Allenstein) is a city in north-eastern Poland.
Olsztyn may also refer to:
- Olsztyn Voivodeship, a former administrative unit in Poland
- Olsztyn, Silesian Voivodeship, a village in south Poland with ruins of a 14th-century castle
- SS Olsztyn, a Hansa A Type cargo ship in service 1947-72