The Seversky Donets or Siverskyi Donets (Russian: Северский Донец; Ukrainian: Сіверський Донець), usually simply called the Donets, is a river on the south of the East European Plain. It originates in the Central Russian Upland, north of Belgorod, flows south-east through Ukraine (Kharkiv, Donetsk and Luhansk Oblasts) and then again through Russia (Rostov Oblast) to join the Don River, about 100 km (62 mi) from the Sea of Azov. The Donets is the fourth largest river in Ukraine and the biggest in the Eastern Ukraine. It is an important source of fresh water in the east of the country.