From the Wikipedia page: 
Sakhalin Oblast (Russian: Сахали́нская о́бласть, tr. Sakhalinskaya oblast; IPA: [səxɐˈlʲinskəjə ˈobləsʲtʲ]) is a federal subject of Russia (an oblast) comprising the Siberia's Sakhalin Island and the Kuril Islands in the Russian Far East. The oblast has an area of 87,100 square kilometers (33,600 sq mi).
After the Russian Revolution and subsequent civil war northern Sakhalin ultimately became governed by the Russian SFSR as a part of Far Eastern Oblast (1922-1926), Far Eastern Krai (1926-1938) and Khabarovsk Krai (included Russian-administered territories of Sakhalin in 1938-1947). Sakhalin Oblast was established on 20 October 1932 as a part of Far Eastern Krai, and became part of Khabarovsk Krai upon the latter foundation in 1938.
Soviet-conquered areas of South Sakhalin and Kuril Islands were declared a South Sakhalin Oblast by the Soviet authorities in a decree issued on 2 February 1946. Almost a year later, on January 2, 1947 the South Sakhalin Oblast was disbanded and included into Sakhalin Oblast, forming present-day boundary of the latter. On the same day Sakhalin Oblast was excluded from Khabarovsk Krai.