Sejny is a town in north-eastern Poland and the capital of Sejny County, in Podlaskie Voivodeship, close to the northern border with Lithuania and Belarus. It is located in the eastern part of the Suwałki Lake Area, on the Marycha river, being a tributary of the Czarna Hańcza. As of 1999 it had almost 6,500 permanent inhabitants, with a strong seasonal increase during the tourist season.

Podlaskie Voivodeship is a voivodeship (province) in northeastern Poland. The name of the province refers to the historical region of Podlachia, and part of its territory corresponds to this region. The capital and largest city is Białystok.