The Siverskyi Donets or Seversky Donets, 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 and then again through Russia to join the Don River, about 100 km (62 mi) from the Sea of Azov. The Donets is the fourth longest river in Ukraine and the biggest in the Eastern Ukraine. It is an important source of fresh water in the east of the country. It gives its name to the Donets Basin, known commonly as the Donbass, an important coal mining region in Ukraine.