From the English Wikipedia page 
Poltava Oblast (Ukrainian: Полтавська область, translit. Poltavs’ka oblast’; also referred to as Poltavshchyna – Ukrainian: Полтавщина) is an oblast (province) of central Ukraine. The administrative center of the oblast is the city of Poltava. Most of its territory is part of the historic Cossack Hetmanate (its southern regions: Poltava, Myrhorod, Lubny, and Hadiach).