Prince of Bourbon-Parma Sixtus

Italian prince of the Parmesan branch of the royal House of Bourbon, Belgian military officer in World War I, and the central figure in the Sixtus Affair, an attempt to negotiate a treaty to end Austria-Hungary's participation in the Great War separate from its Central Powers allies. He also wrote a number of books.

Sixtus was the eldest son of the last Duke of Parma, Roberto I (1848–1907) and his second wife Infanta Maria Antonia of Portugal (1862–1959), daughter of King Miguel of Portugal. His father had had twelve children from a previous marriage and Sixtus was the fourteenth of Duke Robert's twenty four children. Among the twenty four, he was the sixth son, hence he was named, Sixtus.

Prince Sixtus of Bourbon-Parma married Hedwige de la Rochefoucauld (15 February 1896 - 7 May 1986) on 12 November 1919. They had one daughter, Princess Isabella.

Married to a French aristocrat, Prince Sixtus settled in France. In the following years he made several exploratory expeditions to Africa, wrote a number of books (including a biography of his great-great grandmother Maria Luisa of Spain, Duchess of Lucca) and treatises. He died on 14 March 1934 in Paris, aged 47.