Charles I (Karl Franz Joseph Ludwig Hubert Georg Otto Maria) was the last reigning monarch of the Austro-Hungarian Empire. He was the last Emperor of Austria, the last King of Hungary (as Charles IV), the last King of Bohemia (as Charles III), and the last monarch belonging to the House of Habsburg-Lorraine. After his uncle Franz Ferdinand was assassinated in 1914, Charles became the designated successor of the Emperor Franz Josef.
Charles I reigned from 1916 until 1918, when he "renounced participation" in state affairs, but did not abdicate. He spent the remaining years of his life attempting to restore the monarchy until his death in 1922. Beatified by Pope John Paul II in 2004, he is known to the Roman Catholic Church as Blessed Karl of Austria.
In his coronation oath to the Croatian parliament he acknowledged the unity of Croatia, Dalmatia and Slavonia with Rijeka. During the last days of the monarchy he accepted the trialist manifest on creating the Zvonimir's kingdom. He reigned until 1918, when he "renounced participation" in state affairs, but did not abdicate. The Croatian Sabor (parliament) ended the union of Croatia with Hungary and Austria on 29 October 1918 but never dethroned king Karl IV.