Vienna ( vee-EN-ə; German: Wien [viːn] ; Austro-Bavarian: Wean [veɐ̯n]) is the capital, most populous city, and one of nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. Its larger metropolitan area has a population of nearly 2.9 million, representing nearly one-third of the country's population. Vienna is the cultural, economic, and political center of the country, the fifth-largest city by population in the European Union, and the most populous of the cities on the river Danube.

The city lies on the eastern edge of the Vienna Woods (Wienerwald), the northeasternmost foothills of the Alps, that separate Vienna from the more western parts of Austria, at the transition to the Pannonian Basin. It sits on the Danube, and is traversed by the highly regulated Wienfluss (Vienna River). Vienna is completely surrounded by Lower Austria, and lies around 50 km (31 mi) west of Slovakia and its capital Bratislava, 60 km (37 mi) northwest of Hungary, and 60 km (37 mi) south of Moravia (Czech Republic).

The Romans founded a castrum at Vienna, which they called Vindobona, in the 1st century, when the region belonged to the province of Pannonia. It was elevated to a municipium with Roman city rights in 212. This was followed by a time in the sphere of influence of the Lombards and later the Pannonian Avars, when Slavs formed the majority of the region's population.