Ciasne [ˈt͡ɕasnɛ] is a village in the administrative district of Gmina Supraśl, within Białystok County, Podlaskie Voivodeship, in north-eastern Poland. It lies approximately 5 kilometres (3 mi) south-west of Supraśl and 12 km (7 mi) north-east of the regional capital Białystok.