Ostrów Południowy [ˈɔstruf pɔwudˈɲɔvɨ] is a village in the administrative district of Gmina Krynki, within Sokółka County, Podlaskie Voivodeship, in north-eastern Poland, close to the border with Belarus. It lies approximately 6 kilometres (4 mi) west of Krynki, 22 km (14 mi) south-east of Sokółka, and 39 km (24 mi) north-east of the regional capital Białystok.