Black Sea, or Euxine (anc. Pontus Euxinus), is an inland sea lying between Europe and Asia, extending from 41° to 46° 38' N. lat., and from 27° 30' to 41° 50' E. long. Its greatest length from east to west is 720 miles; its greatest breadth, near the west end, 380 miles; and its area, exclusive of the Sea of Azov, is 163,711 sq. m. On the south-western extremity it communicates by the Bosphorus, the Sea of Marmora, and the Dardanelles, with the Mediterranean, and on the north-east by the Strait of Kertch, or Yenikale, with the Sea of Azov. The Black Sea drains nearly one-fourth of the surface of Europe, and also about 114,000 sq. m. of Asia. Throughout its whole extent it has but one island, and that a small one, lying opposite the mouths of the Danube, called Adassi, or Isle of Serpents, on which is a lighthouse. In the centre its depth ranges between 1000 and 1070 fathoms. All the coasts are high, with good harbours, except between the mouths of the Danube and the Crimea; there the land is low, and the danger of navigation greatly increased in winter by the presence of floating ice; for, from the many large rivers which flow into this sea and that of Azov (Danube, Dniester, Bug, Dnieper, Don, Kuban, and Rion, in Europe; and the Kizil-Irmak and Sakaria, in Asia), the waters are fresher than those of the Mediterranean, and consequently easily frozen. There is no tide in this sea, but the large rivers flowing into it give rise to currents, which are particularly strong in spring when the snows melt. There is a strong flow out through the Bosphorus.

From the fall of Constantinople (1453), all but Turkish vessels were excluded from its waters, until the treaty of Kainardji (1774), when the Russians obtained the right to trade in it. Ten years after, Austrian ships were privileged to trade here; and by the Peace of Amiens in 1802 British and French ships were admitted. By the Treaty of Paris (1856) it was opened to the commerce of all nations, and closed to ships of war, while the erection of arsenals was forbidden; but this article was repudiated by Russia in 1870, and in the following March, at a conference in London, the neutralisation of the sea was abrogated. The Bosphorus and Dardanelles are still closed to ships of war other than Turkish and Russian, but the sultan can open them at need to allies.