Which river is the longest in the European Union?

The longest river in the European Union is the Danube.

The Danube is about 2,850 kilometres long, flowing from Germany’s Black Forest region to the Black Sea. It passes through or borders more countries than any other river in the world, including Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Bulgaria, Romania, Moldova and Ukraine. Several European capitals—including Vienna, Bratislava and Budapest—stand on its banks.

The wording can cause confusion because the Danube also flows through countries that are not EU members, such as Serbia, Moldova and Ukraine. In standard geography quizzes, “longest river in the European Union” means the longest major river flowing through the EU, not a river contained entirely within EU territory.

The river’s lower course divides into the Danube Delta before entering the Black Sea. The delta is one of Europe’s most important wetland ecosystems and has been recognized for its exceptional biodiversity. The Rhine is economically important but considerably shorter, while the Loire and Tagus are both close to 1,000 kilometres.