The Kingdom of Croatia-Slavonia (Croatian: Kraljevina Hrvatska i Slavonija; Hungarian: Horvát-Szlavón Királyság; German: Königreich Kroatien und Slawonien) was a nominally autonomous kingdom within the Austro-Hungarian Empire, created in 1868 by merging the kingdoms of Croatia and Slavonia following the Croatian-Hungarian Settlement. It was associated with the Hungarian Kingdom within the dual Austro-Hungarian state, being within the Lands of the Crown of St. Stephen or Transleithania. The kingdom was ruled by the Habsburg Emperor-King of Austria-Hungary (Kaiser und König) under his title as "King of Croatia and Slavonia". The King's appointed steward was the Ban of Croatia and Slavonia. Although it was under the suzerainty of the Crown of Saint Stephen, the Kingdom of Croatia and Slavonia kept a significant level of self-rule.
In 1918, the kingdom declared independence and reformed into the State of Slovenes, Croats and Serbs.