The Danube (/ˈdænjuːb/ dan-ewb, also known by other names) is Europe’s second-longest river, after the Volga River, and also the longest river in the European Union region. It is located in Central and Eastern Europe.
The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries. Originating in Germany, the Danube flows southeast for 2,860 km (1,780 mi), passing through or touching the border of Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before emptying into the Black Sea. Its drainage basin extends into nine more countries.