Włościborek  Włościborek () is a village in the administrative district of Gmina Sępólno Krajeńskie, within Sępólno County, Kuyavian-Pomeranian Voivodeship, in north-central Poland. It lies approximately east of Sępólno Krajeńskie and north-west of Bydgoszcz. The village has a population of 60.