Ostrów [ˈɔstruf] is a village in the administrative district of Gmina Szreńsk, within Mława County, Masovian Voivodeship, in east-central Poland. It lies approximately 6 kilometres (4 mi) east of Szreńsk, 16 km (10 mi) south-west of Mława, and 104 km (65 mi) north-west of Warsaw.