Philip the Handsome

Through Philip the Handsome (1478-1506) ran the genealogical line that joined the Habsburgs to Spain. He was born at Bruges, the son of Maximilian of Austria, later Emperor Maximilian I, and Mary of Burgundy, heiress of the Burgundian Low Countries. His mother's death in 1482 made the four-year-old Philip duke of the Burgundian territories under his father's contested regency; in 1494 he assumed personal rule in the Netherlands, where he pursued a policy of accommodation with France that often diverged from his father's.

In 1496 Philip married Juana, daughter of Ferdinand of Aragon and Isabella of Castile, as part of a double alliance between Habsburg and Trastámara: his sister Margaret of Austria married the Spanish heir, Juan, in the same arrangement. The deaths of Juan in 1497, of his sister Isabella in 1498, and of her infant son Miguel in 1500 left Juana heiress of the Spanish kingdoms — an outcome no one had planned and one that altered European politics for two centuries. Philip and Juana had six children: Eleanor, Charles, Isabella, Ferdinand, Mary, and Catherine; the two sons would later divide the Habsburg world between them.

When Isabella of Castile died in 1504, Juana became queen of Castile, and Philip claimed the government in her right against his father-in-law Ferdinand of Aragon, who sought to retain control as administrator. Philip and Juana sailed for Spain in 1506, and after negotiations Ferdinand withdrew to Aragon, leaving Philip recognized by the Castilian Cortes as King Philip I. Reports of Juana's mental instability, which Philip had reason to emphasize, accompanied the couple's deteriorating marriage.

His reign in Castile lasted only weeks. Philip fell ill at Burgos and died on 25 September 1506, aged twenty-eight. Juana, who never remarried, was eventually confined at Tordesillas, where she remained until her death in 1555. Philip's eldest son inherited the accumulating crowns as Charles V, while the younger, Ferdinand, raised in Spain, received the Austrian lands and the imperial succession; the division of Philip's heritage between his sons created the Spanish and Austrian branches of the dynasty.