Insubria is a historical-geographical region which corresponds to the area inhabited in Classical antiquity by the Insubres; the name can also refer to the Duchy of Milan (1395–1810). For several centuries this name stood for an area stretching approximately between the Adda river in the east and the Sesia river in the west, and between the San Gottardo Pass in the north and the Po river in the south, thus it was a synonym of the Milan region and the surrounding countryside corresponding with Lombardy in modern Italy.

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.