The Black Sea is an inland sea between southeastern Europe and the Anatolian peninsula (Turkey) and is ultimately connected to the Atlantic Ocean via the Mediterranean and Aegean Seas and various straits. The Bosporus strait connects it to the Sea of Marmara, then the long island-bound strait of the Dardenelles to the Aegean Sea region of the Mediterranean. These waters separate eastern Europe and western Asia. The Black sea is also connected to the Sea of Azov by the Strait of Kerch.

The Black Sea has an area of , and a maximum depth of .) Like the Mediterranean Sea, there is a net inflow of seawater through the Bosporus into the oceanic region of some per year, that is lost to evaporation or into geologic faults and so gradually raises the salinity. Freshwater flows in from the surrounding areas, especially central and middle-eastern Europe, per year. The most important river entering the Black Sea is the Danube.

Countries bordering the Black Sea are Turkey, Romania, Bulgaria, Ukraine, Russia, and Georgia. The Crimean peninsula is an autonomous republic of Ukraine. Russia leases a navy base in Sevastopol from Ukraine as a result of the partition of the Black Sea Fleet after the fall of the Soviet Union. The lease of the navy base by Russia in Sevastopol is set to expire in 2017, and is not scheduled for renewal.

Important cities along the coast include: Constanţa (metropolitan area of 550,000 and urban area of 650,000), Mangalia (41,153), Burgas (229,250), Varna (357,752) , Odessa (1,001,000), Kherson (358,000), Sevastopol (379,200), Yalta (80,552), Kerch (158,165), Novorossiysk (281,400), Sochi (328,809), Sukhumi (43,700), Poti (47,149), Batumi (121,806), Trabzon (275,137), Samsun (439,000) and Zonguldak (104,276).