Ciosek [ˈt͡ɕɔsɛk] is a village in the administrative district of Gmina Sośno, within Sępólno County, Kuyavian-Pomeranian Voivodeship, in north-central Poland. It lies approximately 6 kilometres (4 mi) north-east of Sośno, 14 km (9 mi) east of Sępólno Krajeńskie, and 40 km (25 mi) north-west of Bydgoszcz.