The Seversky Donets (Russian: Се́верский Доне́ц) or Siverskyi Donets (Ukrainian: Сіверський Донець, lit. 'Northern 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 (Kharkiv, Donetsk and Luhansk Oblasts) and then again through Russia (Rostov Oblast) to join the river Don, about 100 km (62 mi) from the Sea of Azov. The Donets is the fourth-longest river in Ukraine, and the largest in eastern Ukraine, where it is an important source of fresh water.
https://en.wikipedia.org/wiki/Donets