Olszewko [ɔlˈʂɛfkɔ] is a village in the administrative district of Gmina Nidzica, within Nidzica County, Warmian-Masurian Voivodeship, in Northern Poland. It lies approximately 2 kilometres (1 mi) south-west of Nidzica and 49 km (30 mi) south of the regional capital Olsztyn.