Sejny [ˈsɛi̯nɨ] is a small town in north-eastern Poland, with less than 6,000 inhabitants.
In 1610 the Dominican monks who came to Sejny from Vilnius (Lithuania), started the construction of a large monastery there. The construction of the monastery was finished in 1619 and by 1632 a new church was built nearby, devoted to Holy Mary, Saint George and Saint Hyacinth.