Austria-Hungary (German: Österreich-Ungarn; Hungarian: Osztrák-Magyar Monarchia; Czech: Rakousko-Uhersko; Polish: Austro-Węgry; Ukrainian: Австро-Угорщина; Romanian: Austro-Ungaria; Croatian: Austro-Ugarska; Slovak: Rakúsko-Uhorsko; Serbian: Аустро-Угарска; Slovene: Avstro-Ogrska; Bosnian: Austro-Ugarska; Italian: Austria-Ungheria), also known as the Dual Monarchy or K.u.K. Monarchy, was a dual-monarchic union state, that existed for 51 years (1867–1918) in Central Europe. It replaced the Austrian Empire (1806–1867) on the same territory and originated in a compromise between the ruling Habsburg dynasty and the Hungarians in order to maintain the state. As a multi-national empire in an era of national awakening, it found its political life dominated by disputes among the eleven principal national groups. Its economic and social life was marked by a rapid economic growth through the age of industrialization and social modernization through many liberal and democratic reforms.

The Habsburg dynasty ruled as Emperors of Austria over the western and northern half of the country and as Kings of Hungary over the Kingdom of Hungary, which enjoyed some degree of self-government and representation in joint affairs (principally foreign relations and defence). The federation bore the full name of "The Kingdoms and Lands Represented in the Imperial Council and the Lands of the Crown of St. Stephen".