Since classical times, ancient Greeks, Etruscans and Celts established settlements in the south, the centre and the north of Italy respectively, while various ancient Italian tribes and Italic peoples inhabitated the Italian peninsula and insular Italy. The Italic tribe known as the Latins formed the city of Rome as a Kingdom, which eventually became a Republic that united Italy by the third century BC and emerged as the dominant power of Europe and the Mediterranean Sea as a consequence of the military victories of generals such as Scipio, Aemilius Paullus, Scipio Aemilianus, Gaius Marius, Lucius Sulla, Pompey and Julius Caesar.

In 27 BC, Augustus established the Roman Empire and inaugurated the Pax Romana, a period of stability and relative peace in which Rome flourished as the leading cultural, political and economic capital of the known world. The death of  the last of the good emperors, Marcus Aurelius, in 180 AD and the crisis of the third century marked the end of the Golden Age of Rome. The Empire went through major changes in the following centuries, including the division between a Western and an Eastern half in 284 under Diocletian and the end of the persecutions of Christians with the Edict of Milan of 313 under Constantine. The West collapsed amid barbarian invasions around 476, when Odoacer deposed Romulus Augustulus. Nevertheless, the legacy of the Roman Empire is still wispread and can be observed in the global distribution of the latin script, civilian law, republican governments and Christianity.

During the early middle ages, the Italian peninsula was conquered by the Goths, the Byzantines and the Lombards, until Pope Leo III crowned Charlemagne Holy Roman Emperor the day of Christmas of the year 800 in Rome. The Bishop of Rome and the German Emperor became the universal powers of Italy and Europe, but soon entered in conflict for the investiture controversy and the clash between their factions: the Guelphs and Ghibellines. The struggle for power between the Papacy and the Empire led to the decline of Imperial influence in Italy, especially after the Walk to Canossa of Emperor Henry IV and the victory of Italian forces over Friedrich Barbarossa in the Battle of Legnano: by the 12th century Italy was organized in independent city-states.

The crusades launched by Pope Urban II and his successors proved to be successful for the Italian maritime republics, especially for Venice that entered in control of the mediterranean trade routes and formed a maritime empire (this was also the period of the Venetian-Genoese wars and the voyages of Marco Polo). Therefore Italy first experienced the so-called commercial revolution, which caused the Western economy to shift from agriculture to trade. The social transformations that occured in medieval Italy are also reflected by the appeareance of the first European universities in the peninsula and the beginning of the Renaissance in Florence, Tuscany, during the 14th century.

Renaissance humanism, art, science and exploration marked the transition to the modern era and notable figures such as Leonardo, Dante, Machiavelli, Michelangelo, Giotto, Columbus, Amerigo Vespucci, John Cabot, Giovanni Verrazzano and Galileo made important contributions in their fields between the Trecento and the Seicento. The period was also characterised by the activities of the condottieri in the Italian Renaissance Wars (1494-1559), a long conflict that broke the peace between the city-states and left them exhausted and prey to foreign invasions. The peace of Cateau-Cambresis established Habsburg Spain as the ruler of the South of Italy and Milan. The Duchy of Tuscany and the Venetian Republic remained independent but also weakened by the bankrupcy of the Medici Bank and the rise of the Atlantic route.

Meanwhile, the Papacy reached its zenith of political power by reacting to protestantism with the counter-reformation, a movement that resulted in: the Council of Trent, the activities of the Roman Inquisition, the adoption of the Gregorian Calendar, the emergence of the Baroque and the formation of Holy Leagues to prevent Ottoman expansion in the West. However, the end of the Thirty Years’ War in 1648 and the birth of Westphalian sovereignty diminished Roman Catholic influence in Europe and led to the consolidation of large states, while Italy was fragmented and divided. The 17th and 18th centuries were a period of decline in Italy, except for the cultural impact of the Grand Tour and neoclassicism. Following a series of wars of succession in Europe, Milan went to Habsburg Austria, who later acquired also Tuscany and Venice, and the South passed to the Spanish Bourbons.

Following the Congress of Vienna in 1815, the Risorgimento movement emerged to unite Italy and liberate it from foreign control. After the unsuccessful attempt of 1848, the Italian Wars of Independence against Austria in the North, the Expedition of the Thousand against the Spanish Bourbons in the South, and the capture of Rome that ended Papal temporal power in 1870, resulted in the formation of the nation-state. Giuseppe Mazzini, Giuseppe Garibaldi, King Victor Emmanuel II and Prime Minister Camillo Cavour became known as the four fathers of the fatherland. The new Kingdom of Italy obtained Great Power status, acquired a colonial Empire and rapidly industrialised, although mainly in the north, while the south remained largely impoverished fuelling a large and influential diaspora.

In World War I, Italy joined the Entente with France and Britain, despite having been a member of the Triple Alliance with Germany and Austria-Hungary, and gave a fundamental contribution to the victory of the conflict as one of the so-called Big Four. Italy completed the unification by acquiring Trento and Trieste, and gained a permanent seat in the League of Nations‘s executive council. Nevertheless, Italian nationalists considered World War I a mutilated victory and that sentiment led to the rise of the fascist dictatorship of Benito Mussolini in 1922. The subsequent participation in World War II on the side of Germany and Japan ended in military defeat and an Italian civil war. Following the liberation of Italy, the country abolished the monarchy with a referendum, reinstated democracy, enjoyed an economic miracle, and founded the European Community (later the European Union), NATO and the Group of Six (later the G8 and the G20)