Ostrów Wielkopolski is a city in west-central Poland with 70,982 inhabitants, situated in the Greater Poland Voivodeship; the seat of O…Ostrów Wielkopolski is a city in west-central Poland with 70,982 inhabitants, situated in the Greater Poland Voivodeship; the seat of Ostrów Wielkopolski County. It is the fifth-largest city in the voivodeship after Poznań, Kalisz, Piła and Konin.