Medici, Francesco de' (fränchāsˈkō dā mĕˈdĭchē, Ital. māˈdēchē) [key], 1541–87, grand duke of Tuscany (1574–87); son and successor of Cosimo I de' Medici. In his reign the decline of the Medici family began. He allowed the Austrian and Spanish branches of the house of Hapsburg to establish a virtual protectorate over his dominion, devoting himself to alchemy and other nonpolitical pursuits. He first married Joanna, daughter of Holy Roman Emperor Ferdinand I, and then, after Joanna's death, Bianca Capello. His daughter by the first marriage was Marie de' Medici, queen of Henry IV of France. Francesco was succeeded by his brother, Ferdinand I de' Medici.