||It has been suggested that this article be merged into Kingdom of Croatia-Slavonia. (Discuss) Proposed since March 2017.|
The Triune Kingdom (Croatian: Trojedna kraljevina) was a formal Croatian entity within the Austro-Hungarian Empire. Leaders of the 19th century Illyrian movement maintained that this kingdom existed for most of the second millennium. It comprised three Croatian 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. In Article 1 of the Croatian-Hungarian Settlement of 1868, the territory known as "Lands of the Crown of Saint Stephen" was officially defined 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:
- Privileges – Privilegia Regnorum Croatiae, Dalmatiae et Slavoniae, dated 1377
- Protocols – Protocolla Congregationis generalis Regnorum Croatiae, Dalmatiae et Slavoniae, dated 1557
- Minutes – Acta Congregationum Regni, dated 1562
- Minutes – Transumpta documentorum iura Croatica tangentium, dated 1249
By the end of the 19th century, recognition of the Triune Kingdom was the primary goal of the Independent People's Party, as well as the People's Party of Dalmatia. The term "Triune Kingdom of Dalmatia, Croatia and Slavonia" was used for the medieval Croatian kingdom and for the Habsburg Kingdom of Croatia up to the early 19th century. The term "Triune Kingdom of Croatia, Slavonia and Dalmatia" was used for both the late period (first half of the 19th century) of the Habsburg Kingdom of Croatia, and its successor the Kingdom of Croatia-Slavonia. The order in which Dalmatia was mentioned was a contentious issue, the order differing between the Croatian Hungarian versions of the 1868 Settlement.
- Jakić & Balta 2007, p. 273.
- Romsics & Király 1999, p. 177.
- Korunić 1999, pp. 12–13.
- Goldstein & Jovanović 1999, p. 68.
- Goldstein & Jovanović 1999, p. 77.
- Goldstein & Jovanović 1999, pp. 102-103.
- Kukuljevic-Sakcinski, Ivan von [Hrsg.]. - Zagreb (1874), Codex diplomaticus regni Croatiae, Dalmatiae et Slavoniae 
- Codex diplomaticus regni Croatiae, Dalmatiae et Slavoniae, Volumes 1-2, Tiskom D. Albrechta, 1874, 
- Charles Jelavich, Barbara Jelavich, The Establishment of the Balkan National States, 1804-1920, University of Washington Press, 1977, p. 253
- Romsics & Király 1999, p. 178.
- Barbara Jelavich, History of the Balkans: Twentieth century, 1999 edition, p.57, "The National Party [in Dalmatia] wished to be united with Croatia to form the reconstituted Triune Kingdom."
- Goldstein & Jovanović 1999.
- Sabotič & Matković 2005, p. 168: [...] Zakona o izbornom redu za kraljevinu Dalmacije, Hrvatske i Slavonije
- Mikuláš Teich, Roy Porter, The National Question in Europe in Historical Context, 1993, p.284
- Jakić, Ivana; Balta, Ivan (May 2007). "Pregled zbivanja u predpreporodnom i preporodnom razdoblju do osnivanja političkih stranaka (1841.)". Povijesni zbornik: godišnjak za kulturu i povijesno nasljeđe (in Croatian). Faculty of Philosophy, University of Osijek. 1 (1-2): 273–284. ISSN 1846-3819. Retrieved 2013-12-31.
- Goldstein, Ivo; Jovanović, Nikolina (1999). Croatia: a history. C. Hurst & Co. Publishers. ISBN 1-85065-525-1.
- Romsics, Ignác; Király, Béla K. (1999). Geopolitics in the Danube Region.
- Korunić, Petar (April 1999). "Hrvatski nacionalni program i društvene promjene za revolucije 1848/49. godine" [National Programme and Social Change during the Revolution in 1848-1849.]. Journal - Institute of Croatian History. Faculty of Philosophy, University of Zagreb. 31 (1): 12–13. ISSN 0353-295X. Retrieved 2012-08-21.
- Sabotič, Ines; Matković, Stjepan (April 2005). "Saborski izbori i zagrebačka izborna tijela na prijelazu iz 19. u 20. stoljeće" [Parliamentary Elections and Zagreb Electoral Bodies at the Turn of the 19th and 20th Centuries]. Društvena istraživanja: Journal for General Social Issues (in Croatian). Zagreb, Croatia: Institute of Social Sciences Ivo Pilar. 14 (1-2 (75-76)). ISSN 1330-0288. Retrieved 2012-08-22.