Donetsk, formerly known as Aleksandrovka, Yuzovka, Stalin and Stalino, is an industrial city in eastern Ukraine located on the Kalmius River in the disputed Donetsk region. While internationally recognized as in Ukraine, the city is under the de facto administration of the unrecognized Donetsk People's Republic, which claims it as its capital city. The population was estimated at 905,364 in the city core, with over 2 million in the metropolitan area. According to the 2001 Ukrainian Census, Donetsk was the fifth-largest city in Ukraine.
Administratively, Donetsk has been the centre of Donetsk Oblast, while historically, it is the unofficial capital and largest city of the larger economic and cultural Donets Basin region. Donetsk is adjacent to another major city, Makiivka, and along with other surrounding cities forms a major urban sprawl and conurbation in the region. Donetsk has been a major economic, industrial and scientific centre of Ukraine with a high concentration of heavy industries and a skilled workforce. The density of heavy industries determined the city's challenging ecological situation.