Sejny (Lithuanian: Seinai) is a town in north-eastern Poland, in Podlachian Voivodeship, close to the border with Lithuania and Belarus. It is located in the eastern part of the Suwałki Lake Area (Pojezierze suwalskie), on the Marycha river, being a tributary of Czarna Hańcza. As of 1999 it had almost 6,500 permanent inhabitants, with many more inhabitating the area in the tourist season, and was the capital of a separate powiat.

Currently Sejny is a notable centre of trade, production and tourism, with thousands of them visiting the town every year. A milk plant and a cheese factory are located in the town, as well as numerous hotels. Sejny is also a notable centre of cultural life of the Lithuanian minority in Poland. It is the main seat of the Lithuanian Society of Poland and the Aušra bi-weekly. According to some sources, the number of Lithuanians living in the town and the powiat surrounding it is close to 30%. Due to that, there is a Lithuanian consulate there, as well as a Lithuanian school.

Lithuanian's in Poland