Austria-Hungary, often referred to as the Austro-Hungarian Empire or the Dual Monarchy, was a multi-national constitutional monarchy in Central Europe between 1867 and 1918. Austria-Hungary was a military and diplomatic alliance of two sovereign states with a single monarch who was titled both emperor of Austria and King of Hungary. Austria-Hungary constituted the last phase in the constitutional evolution of the Habsburg monarchy: it was formed with the Austro-Hungarian Compromise of 1867 in the aftermath of the Austro-Prussian War and was dissolved shortly after Hungary terminated the union with Austria on 31 October 1918.

The Habsburg monarchy, also known as Habsburg Empire, or Habsburg Realm, was the collection of empires, kingdoms, duchies, counties and other polities that were ruled by the House of Habsburg. From the 18th century it is also referred to as the Danubian monarchy or the Austrian monarchy.