Syeverodonetsk, city, eastern Ukraine, in the valley of the Donets River. The city was founded in 1934 as the site of a new chemical complex, part of which was evacuated eastward during World War II. In 1951 and 1958 additional chemical industries were added, based on coke, and the complex has grown over the years. With nearby Lysychansk and Rubizhne, it is one of Ukraine’s major chemical centres. Pop. (2001) 72,531; (2005 est.) 69,763.