The Congress of Vienna (French: Congrès de Vienne, German: Wiener Kongress) of 1814–1815 was an international diplomatic conference to reconstitute the European political order after the downfall of the French Emperor Napoleon I. It was a meeting of ambassadors of European states chaired by Austrian statesman Klemens von Metternich, and held in Vienna from September 1814 to June 1815.

The objective of the Congress was to provide a long-term peace plan for Europe by settling critical issues arising from the French Revolutionary Wars and the Napoleonic Wars. The goal was not simply to restore old boundaries but to resize the main powers so they could balance each other and remain at peace. More fundamentally, the conservative leaders of the Congress sought to restrain or eliminate the republicanism and revolution which had upended the constitutional order of the European old regime, and which continued to threaten it. In the settlement, France lost all its recent conquests, while Prussia, Austria and Russia made major territorial gains. Prussia added smaller German states in the west, Swedish Pomerania, 60% of the Kingdom of Saxony, and the western part of the former Duchy of Warsaw; Austria gained Venice and much of northern Italy. Russia gained the central and eastern part of the Duchy of Warsaw. It ratified the new Kingdom of the Netherlands which had been created just months before from the formerly Austrian territory that in 1830 became Belgium.

The immediate background was Napoleonic France's defeat and surrender in May 1814, which brought an end to 23 years of nearly continuous war. Negotiations continued despite the outbreak of fighting triggered by Napoleon's dramatic return from exile and resumption of power in France during the Hundred Days of March to July 1815. The Congress's "final act" was signed nine days before his final defeat at Waterloo on 18 June 1815.

Historians have criticized the Congress for causing the subsequent suppression of the emerging national and liberal movements, and it has been seen as a reactionary movement for the benefit of traditional monarchs.

In a technical sense, the "Congress of Vienna" was not properly a congress: it never met in plenary session. Instead, most of the discussions occurred in informal, face-to-face sessions among the Great Powers of Austria, Britain, France, Russia, and sometimes Prussia, with limited or no participation by other delegates. On the other hand, the Congress was the first occasion in history where, on a continental scale, national representatives came together to formulate treaties instead of relying mostly on messages among the several capitals. The Congress of Vienna settlement formed the framework for European international politics until the outbreak of the First World War in 1914.