Date of Birth: 12 June 1519
Spouse: Eleanor, daughter of Pedro Álvarez de Toledo, Marquis of Villafranca, and Maria Osorio, then Camilla, daughter of Antonio Martelli and Elisabetta Soderini
Reign: 1569 – 1574
Summary: Cosimo won renown for the Medici family like none other before him. Born in Florence to a Medici condottiere, Cosimo became Duke of Florence at the age of 17 when his cousin, Alessandro, was assassinated leaving no legitimate heir. The new duke was relatively unknown in Florence but he was viewed as capable and many hoped to use the duke as a pawn in their own schemes. When Cosimo took over leadership of Florence, he was not so easily manipulated. Exiled Florentines marched on the city in 1537 with French support and Cosimo defeated them soundly, solidifying his rule in Florence. Holy Roman Emperor Charles V recognized his authority over Florence that same year and invested the Medici family with complete control over the duchy. Cosimo began a small expansionist movement a few years later. In 1554, he laid siege to Siena. By 1559, all of Siena was under Florentine control. In recognition of his mastery of north-central Italy, Pope Pius V elevated Cosimo to the rank of Grand Duke of Tuscany in 1569.
Cosimo ruled with an iron fist, employing Swiss mercenaries to do his dirty work. He even had his relative, Lorenzino de Medici, assassinated to further solidify his claim to Florence. He was also an active builder. He expanded the military and public buildings across his realm, placing a heavy tax burden on the people. His most famous building was the Uffizi which today houses Florence's most famous art museum. Cosimo expanded the Florentine navy and founded the heraldic Order of Saint Stephen. By 1564, he resigned from active politics leaving the government of Florence then Tuscany to his son, Francesco. His two other surviving sons both died of malaria. Cosimo eventually died at his Villa di Castello in the Florentine countryside. His son then succeeded him as grand duke.
Date of Death: 21 April 1574
Successor: Francesco I
Other Monarch Deaths:
Alexander II, pope of Rome (1073)
Frederick IV, duke of Lorraine (1329)
Henry VII, king of England (1509)