Prince Ferdinand Pius, Duke of Calabria and Castro, was head of the House of Bourbon-Two Sicilies and pretender to the throne of the extinct Kingdom of the Two Sicilies from 1934 to 1960.

The House of Bourbon-Two Sicilies is a cadet branch of the House of Bourbon that ruled Southern Italy and Sicily for more than a century in the 18th and 19th centuries. It descends from the Capetian dynasty in legitimate male line through Philip, Duke of Anjou, a younger grandson of Louis XIV of France (1638–1715) who established the Bourbon dynasty in Spain in 1700 as Philip V (1683–1746). In 1759, King Philip's younger grandson was appanaged with the kingdoms of Naples and Sicily, becoming Ferdinand IV and III (1751–1825), respectively, of those realms. His descendants occupied the joint throne, merged as the "Kingdom of the Two Sicilies" in 1816, until 1861, claimed it thereafter from exile, and constitute the extant Bourbon-Two Sicilies family.