Karl was born in Vienna, Austria-Hungary, the youngest son of Archduke Leopold Salvator of Austria and of his wife Blanca de Borbón y de Borbón-Parma. His mother was the eldest daughter of Carlos, Duke of Madrid, Carlist claimant to the throne of Spain. Karl was given the baptismal names Carolus Pius Maria Adelgonda Blanka Leopoldus Ignatius Raphael Michael Salvator Chrillus Angelus Barbara. His godparents were Pope Pius X and the Countess of Bardi. Karl grew up in the Palais Toskana which formerly stood in Argentinierstrasse in Vienna. In 1919 the republican government of Austria confiscated all the properties of the Habsburgs. Karl moved with his family first to Tenuta Reale, a villa belonging to his mother's family near Viareggio in Italy. Then they moved to Barcelona in Spain. In 1926 he was given Spanish nationality. After completing high-school Karl entered the Industrial Engineering School. He returned to Austria in the early 1930s and joined the Heimwehr, a conservative militia which engaged in street fights with Communists and Socialists.
The cruzadistas
In 1932 a section of the Carlist movement, called cruzadistas from the name of the magazine El Cruzado Español, began to entrust their hopes for the future of Carlism to the sons of Blanca de Borbón. At the time the Carlist claimant Alfonso Carlos, Duke of San Jaime, Karl's great-uncle, was in his eighties and childless. There were no other male-line descendants of the first Carlist claimant Carlos V. The cruzadistas held that Alfonso XIII, constitutional king of Spain, and his sons were excluded from the succession on account of their liberalism. The cruzadistas also believed that the more junior male lines of the House of Bourbon were also permanently excluded from the Spanish succession; some, like the Bourbon-Sicilies, were held to be excluded because they had recognised Alfonso as constitutional king of Spain, while others, like the Bourbon-Parmas, were held to be excluded because of French nationality. Since the cruzadistas believed that there were no more male members of the House of Bourbon eligible to succeed to the Spanish throne, they held that the Carlist claim should pass at the death of Alfonso Carlos to the sons of his closest female relative, Blanca de Borbón. This was a minority view in the Carlist movement, and one which was condemned by Alfonso Carlos himself. As long as Alfonso Carlos lived, Blanca and her sons, including Karl, were hesitant to press their claims. When Alfonso Carlos died in 1936, Karl at first supported the regent of the Carlist Communion, Prince Xavier of Bourbon-Parma, who had been appointed by Alfonso Carlos. In the confused circumstances of the Spanish Civil War Karl did not make any immediate claim to the throne.
Carlist claimant
On 29 June 1943 Karl issued a manifesto in which he claimed to be the legitimate successor to the Spanish throne. At the time, he had three older brothers still living, but none of these had shown an interest in claiming the throne for himself. In 1947 Karl's older brothers Leopold and Franz Josef formally renounced their rights in New York City. In 1948 his other brother Anton verbally renounced his rights in Barcelona. Karl was recognised by his supporters as Carlos VIII; his movement is therefore called carloctavismo or octavismo. He used the title Duke of Madrid as his grandfather had done. Karl received the support of some of the most conservative Carlist leaders. He also received a certain level of support from some of General Franco's officials in the Movimiento Nacional; the followers of the Carlist regent Prince Xavier of Bourbon-Parma claimed that the Francoist support was merely an attempt to divide Carlists. Karl moved to Andorra and then returned to Barcelona. Between 1944 and 1951 he gave out fourteen titles of nobility; he also named members to the Order of Proscribed Legitimacy and the Order of Santa Maria of the Lily of Navarre. He established a new order of merit named in honour of Saint Charles Borromeo. In 1952 he awarded the collar of this order to General Franco and the grand cross of the order to Cardinal Federico Tedeschini, papal legate to the International Eucharistic Congress in Barcelona.
Marriage and family
On 8 May 1938, in St. Stephen's Cathedral in Vienna, Karl married Christa Satzger de Bálványos, daughter of Geza Satzger de Bálványos and of his wife, Maria Alexandrina Friedmann. The marriage was morganatic, and the children born to it had no dynastic rights of succession. Karl and Christa had two daughters:
Alejandra Blanca de Habsburgo, married in 1960 to José María Riera Leyva.
María Inmaculada Pía de Habsburgo, married on 18 Dec 1969 in Arlington, Virginia, to John Howard Dobkin . Countess Inmaculada devoted her professional life to bolstering Spanish and American relations, successfully running the Queen Sofia Spanish Institute in New York, as its CEO. She continues to live in Manhattan.
On 30 November 1990, Alejandra and Inmaculada were each given the title Countess of Habsburg by Archduke Otto of Austria. Christa left Karl in 1949. In December 1950, they received a civil divorce in Reno, Nevada. On 4 January 1951, Karl initiated a process petitioning for an ecclesiastical decree of nullity; the case had not been resolved at his death.
Death
Karl died of a cerebral hemorrhage24 December 1953, in Barcelona, Spain. Several funeral masses were celebrated for him, including one on 16 January 1954 in Madrid, attended by numerous government officials and members of the diplomatic corps. He was buried in the Monastery of Santa Maria de Poblet.