The Southern Bug, also called Southern Buh (Ukrainian: Південний Буг, romanized: Pivdennyi Buh; Russian: Южный Буг, romanized: Yuzhny Bug; Crimean Tatar: Aq Suv; Romanian: Bugul de Sud or just Bug), and sometimes Boh River (Ukrainian: Бог; Polish: Boh), is a navigable river located in Ukraine. It is the second-longest river flowing exclusively in Ukraine. While located in relatively close proximity, the river should not be confused with Western Bug or Bug which flows in opposite direction towards Baltics. The source of the Southern Bug is in the west of Ukraine, in the Volhynian-Podolian Upland, about 145 kilometres (90 miles) from the Polish border, from where it flows southeasterly into the Bug Estuary (Black Sea basin) through the southern steppes (see Granite-steppe lands of Buh park). It is 806 kilometres (501 miles) long and drains 63,700 square kilometres (24,600 sq mi). Several regionally important cities and towns in Ukraine are located on the Southern Bug. Beginning in Western Ukraine and moving downstream, in a southeasterly direction, they are: Khmelnytskyi, Khmilnyk, Vinnytsia, Haivoron, Pervomaisk, Voznesensk and Mykolaiv. On several occasions the river served as an international border. At least following the 1768–1774 Russo-Turkish War, and more narrowly the Chyhyryn campaigns, the river became a border between the Imperial Russia and Ottomans. Some 200 years later between 1941 and 1944 during World War II the Southern Bug formed the border between German-occupied Ukraine (Reichskommissariat Ukraine) and the Romanian-occupied part of Ukraine, called Transnistria.
