Black Sea (ancient Pontus Euxinus), inland sea, lying between southeastern Europe and Asia Minor. It is connected with the Aegean Sea by the Bosporus, the Sea of Marmara, and the Dardanelles. Romania, Bulgaria, and the European portion of Turkey bound it on the west. The northern and eastern shores are bordered by Ukraine, Russia, and Georgia; the entire southern shore is Turkish territory.
The Black Sea has a length of about 1200 km (about 750 mi) from east to west, a maximum width of 610 km (380 mi), and an area (excluding its northern arm, the Sea of Azov) of about 436,400 sq km (about 168,500 sq mi). The Crimean Peninsula projects into the Black Sea from the north, forming the shallow Sea of Azov on the east and the Karkinitskiy Gulf on the west. The former is almost entirely cut off from the Black Sea. The sea receives the drainage of a large part of central and eastern Europe through the Dnepr, Dnestr, Southern Bug, and Danube rivers. It also receives waters from a considerable section of eastern European Russia, through the Don River (which flows into the Sea of Azov) and from the western Caucasus region through the Kuban (which also flows into the Sea of Azov), and a number of smaller rivers; and the Black Sea drains northern Asia Minor through the Çoruh (Chorokh), Yesil Irmak, Kizilirmak, and Sakarya rivers. The floor of its single central basin lies about 1830 m (about 6000 ft) below the surface, and the greatest depth exceeds 2135 m (about 7000 ft). Severe storms occur frequently on the sea, particularly during the winter season. The prevailing winter winds are from the north.
The Black Sea is abundantly stocked with valuable sturgeon and other fish. As an outlet for the products of Ukraine and adjoining republics, it is of special importance in regional commerce. The principal ports are Odesa, Kherson, and Sevastopol' in Ukraine; P'ot'i and Bat'umi in Georgia; Novorossiysk in Russia; Constanta in Romania; Burgas and Varna in Bulgaria; and Eregli, Samsun, Sinop, and Trabzon in Turkey.
Navigation in the Black Sea began early. Many of the colonial and commercial activities of ancient Greece and Rome, and in later times of the Byzantine Empire, centered on it. For almost three centuries after 1453, when the Ottoman Turks occupied Constantinople, the modern capital and last stronghold of the Byzantine Empire, the sea was virtually closed to foreign commerce. The Russian Empire began to challenge Turkish supremacy in the Black Sea early in the 18th century. By the terms of the Treaty of Paris of 1856, which ended the Crimean War, the sea was opened to the commerce of all nations and was neutralized. In 1870 Alexander II, emperor of Russia, repudiated the neutralization section of the Treaty of Paris and placed a naval force in the Black Sea. A conference of European powers, held in 1871, sanctioned this action, but reaffirmed the right of the Turkish sultan to close the Dardanelles and the Bosporus to war vessels. Following the defeat of Turkey in the Russo-Turkish War of 1877-78, the Russians gained important rights for their Black Sea commerce. During World War I the Russian fleet in the Black Sea was active against Turkey.