Carinthian Plebiscite

The Carinthian plebiscite (German: Kärntner Volksabstimmung, Slovene: Koroški plebiscit) was held on 10 October 1920 in the area predominantly settled by Carinthian Slovenes. It determined the final southern border between the Republic of Austria and the newly formed Kingdom of Serbs, Croats and Slovenes (later Yugoslavia) after World War I.

After the defeat of the multi-ethnic Austro-Hungarian Monarchy and the ruling Habsburg dynasty in World War I, new states arose in its former territory. Among these there was an internationally unrecognized State of Slovenes, Croats and Serbs, which was created in the final days of the war according to the 1917 Corfu Declaration, and merged with the Kingdom of Serbia to form the new South Slavic Kingdom of Serbs, Croats and Slovenes on December 1, 1918.

Determination of borders between the new countries was complex and difficult, and not always peaceful: While the northeastern border with the Kingdom of Italy along the "Julian March" was already determined by the 1915 Treaty of London, the demarcation line between Yugoslavia and the rump state of German-Austria was a difficult and highly disputed matter. The principle of self-determination, championed by U.S. President Woodrow Wilson, was taken up by both Slovenes and German-Austrians in the Carinthian, Styrian and Carniolan lands of the defunct Habsburg empire. The rising tensions culminated in clashes of arms, as on Marburg's Bloody Sunday in Lower Styria and the continued fighting of paramilitary groups in southeastern Carinthia.