Gian Galeazzo Visconti (1351-1402) was the first Duke of Milan, ruling from 1395 until his death. He was a member of the Visconti family, a powerful dynasty in northern Italy. Under his leadership, Milan expanded its territory and influence, becoming a significant political and cultural center during the late Middle Ages. Gian Galeazzo was known for his ambitious projects, including the construction of the Castello Sforzesco and the development of the Navigli canals. He also played a crucial role in the politics of the Italian city-states, often engaging in alliances and conflicts to strengthen his power and control over the region.