- Rostov Oblast (Russian: Росто́вская о́бласть, romanized: Rostovskaya oblast’, IPA: [rɐˈstofskəjə ˈobləsʲtʲ]) is a federal subject of Russia (an oblast), located in the Southern Federal District. The oblast has an area of 100,967 square kilometers (38,984 sq mi) and a population of 4,200,729 (2021 Census), making it the sixth most populous federal subject in Russia. Its administrative center is the city of Rostov-on-Don, which also became the administrative center of the Southern Federal District in 2002.