Siemieniakowszczyzna [ɕɛmjɛɲakɔfʂˈt͡ʂɨzna] is a village in the administrative district of Gmina Narewka, within Hajnówka County, Podlaskie Voivodeship, in north-eastern Poland, close to the border with Belarus. A place with the longest single-word name in Poland (20 letters).
