Ciemniewo [t͡ɕɛmˈɲɛvɔ] is a village in the administrative district of Gmina Sońsk, within Ciechanów County, Masovian Voivodeship, in east-central Poland. It lies approximately 4 kilometres (2 mi) north-east of Sońsk, 12 km (7 mi) south-east of Ciechanów, and 67 km (42 mi) north of Warsaw.