Austria-Hungary (also known as the Austro-Hungarian Empire, Austro-Hungarian Monarchy or K.u.K. Monarchy, Dual Monarchy, Danube Monarchy), more formally known as the Kingdoms and Lands Represented in the Imperial Council and the Lands of the Holy Hungarian Crown of Saint Stephen, was a constitutional monarchic union between the crowns of the Austrian Empire and the Kingdom of Hungary in Central Europe, which operated from 1867 to October 1918, following the end of World War I. The union was a result of the Austro-Hungarian Compromise of 1867, under which the House of Habsburg agreed to share power with the separate Hungarian government, dividing the territory of the former Austrian Empire between them. The Austrian and the Hungarian lands became independent entities enjoying equal status.
Austria-Hungary was a multinational realm and one of the world's great powers at the time. Austria-Hungary was geographically the second largest country in Europe after the Russian Empire (621,538 square kilometres (239,977 sq mi)), and the third most populous (after Russia and the German Empire). The Empire built up the fourth largest machine building industry of the world (after the United States, German Empire and the United Kingdom).
The Austro-Hungarian Empire consisted of two monarchies (Austria and Hungary), and three autonomous regions: Polish Galicia within Austrian Empire (from 1867) and Croatia within Kingdom of Hungary (from 1868), and a common Austro-Hungarian autonomous territory: Bosnia and Herzegovina (from 1910).
The dual monarchy existed for 51 years until it dissolved on 31 October 1918 at the end of World War I. Many modern-day nation states have emerged in the territory formerly belonging to the realm. These include Austria, Hungary, Slovenia, Bosnia and Herzegovina, Croatia, the Czech Republic, Slovakia, large parts of Serbia and Romania, and smaller parts of Italy, Montenegro, Poland and Ukraine.
Charles I of Austria or Charles IV of Hungary (Karl Franz Joseph Ludwig Hubert Georg Otto Marie; 17 August 1887 – 1 April 1922) was, among other titles, the last ruler of the Austro-Hungarian Empire. He was the last Emperor of Austria, the last King of Hungary, and the last monarch of the House of Habsburg-Lorraine. He reigned from 1916 until 1919, 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. Following his beatification by the Catholic Church in 2004, he has become commonly known as Blessed Charles of Austria.