Austria-Hungary (also known as the Austro-Hungarian Empire or the Dual Monarchy) was a constitutional union of the Empire of Austria and the Apostolic Kingdom of Hungary that existed from 1867 to 1918, when it collapsed as a result of defeat in World War I. The union was a result of the Compromise of 1867. It was ruled by the House of Habsburg, constituting the last phase in the constitutional evolution of the Habsburg Monarchy.