Philip I of Castile (b. 1478)
Philip the Handsome (22 July 1478 – 25 September 1506), also called the Fair, was ruler of the Burgundian Netherlands and titular Duke of Burgundy from 1482 to 1506 and the first Habsburg King of Castile (as Philip I) for a brief time in 1506.

The son of Maximilian I, Holy Roman Emperor and Mary of Burgundy, Philip was less than four years old when his mother died, and upon her death, he inherited the Burgundian Netherlands. Despite his young age, Philip quickly proved himself an effective ruler beloved by his people in the Low Countries, pursuing policies that favoured peace and economic development, while maintaining a steady course of government building.

In 1496, his father arranged for him to marry Joanna, the second daughter of Queen Isabella I of Castile and King Ferdinand II of Aragon. Around the same time, Philip's sister Margaret was given in marriage to Joanna's brother John, Prince of Asturias. After the deaths of her elder siblings John and Isabella and her infant nephew Miguel, Joanna became heir presumptive to the thrones of Castile and Aragon. Most of Philip's time in Spain was spent consolidating his power, often leading to conflicts against his wife and her father. Joanna became Queen of Castile when her mother died in 1504. Philip was proclaimed King in 1506, but died a few months later, leaving his wife distraught with grief, eventually leading to her father and son Charles seizing power from Joanna and leaving her imprisoned for the rest of her life on account of her alleged insanity.

Philip was the first Habsburg monarch in Spain, and every Spanish monarch since his son Charles V, Holy Roman Emperor, has been one of his descendants. Philip died before his father, and therefore never inherited his father's territories or became Holy Roman Emperor. However, his son Charles eventually united the Habsburg, Burgundian, Castilian, and Aragonese inheritances. By inheriting the Burgundian Netherlands and acquiring much of Spain and its possessions in the New World by marriage to Joanna, Philip was instrumental in vastly enhancing the territories of the Habsburgs, and his progeny would dominate European history for over the next five centuries.