Charles I or Karl I was Emperor of Austria, King of Hungary, King of Croatia, King of Bohemia, and the last of the monarchs belonging to the House of Habsburg-Lorraine to rule over Austria-Hungary. The son of Archduke Otto of Austria and Princess Maria Josepha of Saxony, Charles became heir presumptive of Emperor Franz Joseph after his uncle Archduke Franz Ferdinand of Austria was assassinated in 1914. In 1911, he married Princess Zita of Bourbon-Parma. He is venerated in the Catholic Church, having been Beatified by Pope John Paul II on 3 October 2004, Charles is known to the Catholic Church as Blessed Karl of Austria.
Charles succeeded to the thrones in November 1916 following the death of his granduncle, Franz Joseph. He made secret attempts to negotiate Austria-Hungary's exit from the First World War but was unsuccessful. Despite Charles's efforts to preserve the empire by transforming it into a federal union, Austria-Hungary hurtled towards disintegration: Czechoslovakia and the State of Slovenes, Croats and Serbs were proclaimed, and Hungary broke monarchic ties to Austria by the end of October 1918.