Gian Galeazzo Visconti, was the first duke of Milan (1395) and ruled the late-medieval city just before the dawn of the Renaissance. He also ruled Lombardy jointly with his uncle Bernabò. He was the founding patron of the Certosa di Pavia, completing the Visconti Castle at Pavia begun by his father and furthering work on the Duomo of Milan. He captured a large territory of Northern Italy and the Po valley. He threatened war with France in relation to the transfer of Genoa to French control as well as issues with his beloved daughter Valentina. When he died of fever in the Castello of Melegnano, his children fought with each other and fragmented the territories that he had ruled.

The Duchy of Milan was a state in Northern Italy, created in 1395 by Gian Galeazzo Visconti, then the lord of Milan, and a member of the important Visconti family, which had been ruling the city since 1277.