Triune Kingdom

The Triune Kingdom (Croatian: Trojedna kraljevina) was a formal Croatian entity within the Austro-Hungarian Empire. It comprised three realms, Dalmatia, Slavonia, and Croatia proper—which, despite their political and administrative separation, were united under a single king.

Prior to 1848, the Croatians claimed territories contested by both the Hungarians and the Vienna Court War Council, within the Austro-Hungarian empire, and also by the Ottoman Empire. During the Revolutions of 1848, Croatian nationalists proposed the establishment of the independent Triune Kingdom, which would be a Croatian cultural and political union. Political representatives of Croatia advocated the notion to the Emperor, and demanded the unification of the three kingdoms.

Following the Austro-Hungarian Compromise of 1867 and the Croatian-Hungarian Settlement of 1868, the Hungarian claims on Slavonia, and the Austrian claims on the Military Frontier, were formally relinquished; but there was no change in the status of Dalmatia. Despite that, Article 1 of the Croatian-Hungarian Settlement of 1868 defined the territory known as "Lands of the Crown of Saint Stephen" as "a state union of the Kingdom of Hungary and the Kingdoms of Dalmatia, Croatia and Slavonia".

In 1874, Ivan Kukuljević Sakcinski published various findings from archival collections—in his work Codex Diplomaticus, now kept in the Croatian State Archives—documents from all periods that speak of the Kingdom of Croatia, Dalmatia and Slavonia, consisting of:

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