Cosimo I de' Medici, Grand Duke of Tuscany (died 1574)

Cosimo I de' Medici was the second and last duke of Florence from 1537 until 1569, when he became the first grand duke of Tuscany, a title he held until his death. Cosimo I succeeded his cousin to the duchy. He built the Uffizi (office) to organize his administration, and conquered Siena to consolidate Florence's rule in Tuscany. He expanded the Pitti Palace and most of the Boboli Gardens were also laid out during his reign.