Białystok voivodeship. Administrative unit in northeastern Poland, having an area of 23,200 sq km and a population of 1.2 million (1974). The southeastern part of the province includes northern Podlachia (ie, the southern portions of Siemiatycze, Hajnówka, and Bielsk Podlaski counties), which, until the expulsion of the Ukrainian population in 1945–7, was Ukrainian ethnic territory (2,700 sq km; pop 80,000).