Austro-Hungarian Compromise of 1867
The Austro-Hungarian Compromise of 1867 (German: Ausgleich, Hungarian: kiegyezés) established the dual monarchy of Austria-Hungary, which was a military and diplomatic alliance of two sovereign states. The Compromise only partially re-established the former pre-1848 sovereignty and status of the Kingdom of Hungary, being separate from, and no longer subject to, the Austrian Empire.
Source: Wikipedia — Austro-Hungarian Compromise of 1867 (CC BY-SA 4.0)