Ostaszewo [ɔstaˈʂɛvɔ] is a village in the administrative district of Gmina Grodziczno, within Nowe Miasto County, Warmian-Masurian Voivodeship, in northern Poland. It lies approximately 5 kilometres (3 mi) south-east of Grodziczno, 16 km (10 mi) east of Nowe Miasto Lubawskie, and 64 km (40 mi) south-west of the regional capital Olsztyn.