Duchy of Milan in the context of "Milan"

A city-state is an independent sovereign city which serves as the center of political, economic, and cultural life over its contiguous territory, as opposed to a regular state or country comprising a capital city and other cities and/or a countryside. City-states have existed in many parts of the world throughout history, including cities such as Rome, Carthage, Athens and Sparta and the Italian city-states during the Middle Ages and Renaissance, such as Florence, Venice, Genoa and Milan.

With the rise of nation states worldwide, there remains some disagreement on the number of modern city-states that still exist; Singapore, Monaco and Vatican City are the candidates most commonly discussed. Out of these, Singapore is the largest and most populous city-state in the world, with full sovereignty, international borders, its own currency, a robust military, and substantial international influence in its own right. The Economist refers to it as the "world's only fully functioning city-state".

Italy, up until its unification in 1861, was a conglomeration of city-states, republics, and other independent entities. The following is a list of the various Italian states during that period. Following the fall of the Western Roman Empire and the arrival of the Middle Ages (in particular from the 11th century), the Italian Peninsula was divided into numerous states. Many of these states consolidated into major political units that balanced the power on the Italian Peninsula: the Papal States, the Venetian Republic, the Republic of Florence, the Duchy of Milan, the Kingdom of Naples and the Kingdom of Sicily. Unlike all the other Italian states of the medieval and early modern period, the republics of Venice and Genoa, thanks to their maritime power, went beyond territorial conquests within the Italian Peninsula, conquering various regions across the Mediterranean and Black Seas.

Gian Galeazzo Visconti (16 October 1351 – 3 September 1402), was the first duke of Milan (1395) and ruled that 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 House of Sforza (Italian: [ˈsfɔrtsa]) was a ruling family of Renaissance Italy, based in Milan. Sforza rule began with the family's acquisition of the Duchy of Milan following the extinction of the Visconti family in the mid-15th century and ended with the death of the last member of the family's main branch, Francesco II Sforza, in 1535.

The Hispanic Monarchy (Monarquía Hispánica in Spanish), also known as the Catholic Monarchy and historically referred to as the Monarchy of Spain, was the political entity encompassing the territories and dependencies of the Spanish Empire between 1479 and 1716. These regions maintained distinct, individual public institutions, councils, and legal systems, but were united under the control of a superior entity (the King of Spain) and common state institutional structures. This monarchy was administered under a polysynodial system of councils. The Spanish monarch acted as king (or with the corresponding title) according to the political constitution of each kingdom, state, or lordship, and thus, their formal power varied from one territory to another. However, they acted as a unified monarch over all the territories of the monarchy, almost like a Composite Monarchy.

The Monarchy included the Crown of Castile—with Granada, Navarre and the kingdoms of the Indies—and Aragon—with Sicily, Naples, Sardinia, Malta and the State of the Presidi—, Portugal and its overseas territories between 1580 and 1640, the territories of the Burgundian Circle except between 1598–1621—Franche-Comté, the Netherlands, as well as Charolais—, the Duchy of Milan, the Marquisate of Finale, the Spanish East Indies, and Spanish Africa.

The Kingdom of Lombardy–Venetia, commonly called the "Lombardo-Venetian Kingdom", was a constituent land (crown land) of the Austrian Empire from 1815 to 1866. It was created in 1815 by resolution of the Congress of Vienna in recognition of the Austrian House of Habsburg-Lorraine's rights to the former Duchy of Milan and the former Republic of Venice after the Napoleonic Kingdom of Italy, proclaimed in 1805, had collapsed.

The kingdom survived for only fifty years—the region of Lombardy was ceded to France in 1859 after the Second Italian War of Independence, which then immediately ceded it to the Kingdom of Sardinia. Lombardy-Venetia was finally dissolved in 1866 when its remaining territory was incorporated into the recently proclaimed Kingdom of Italy following the kingdom's victory against Austria in the Third Italian War of Independence.