Rivne Oblast (Ukrainian: Рі́вненська о́бласть, romanized: Rivnenska oblast), also referred to as (Ukrainian: Рі́вненщина) is an oblast (province) of Ukraine. Its administrative center is Rivne. The surface area of the region is 20,100 km². Its population is: 1,148,456. Previously part of the Second Republic of Poland's Wojewódstwo Wołyńskie and earlier the Ukrainian People's Republic's Volhynian Governorate, the Rivne Oblast was created as part of the Ukrainian Soviet Socialist Republic on December 4, 1939 after the Soviet invasion and occupation of eastern Poland on 17 September 1939.