With the Frankish conquest of Italy in the 8th century, the Carolingians assumed the title, which was maintained by subsequent Holy Roman Emperors throughout the Middle Ages.

Later, the Germanic foederati, the Scirians and the Heruli, as well as a large segment of the Italic Roman army, proclaimed Odoacer Rex Italiae ('King of Italy).

In 568, the Lombards entered the peninsula and ventured to recreate a barbarian kingdom in opposition to the Empire, establishing their authority over much of Italy, except the Exarchate of Ravenna and the duchies of Rome, Venetia, Naples and the southernmost portions.

In the 8th century, estrangement between the Italians and the Byzantines allowed the Lombards to capture the remaining Roman enclaves in northern Italy.

After the death of Charles the Fat in 887, Italy fell into instability and a number of kings attempted to establish themselves as independent Italian monarchs.

The monarchy was superseded by the Italian Republic, after a constitutional referendum was held on 2 June 1946, after World War II.

Roman authority in Italy was briefly re-established under Justinian, though his gains were lost under his successor Justin II, after a new Germanic tribe, the Lombards, invaded from the north and established their kingdom in 568.

Central Italy, along the Rome-Ravenna axis, was part of the Papal States, under the direct personal rule of the pope.

This client state did not survive the end of the Napoleonic era; in its place, the Congress of Vienna established a number of independent duchies and kingdoms in the region.

This title is present in Italian laws proclaimed by Napoleon I: [Name], by the Grace of God and the Constitutions, Emperor of the French and King of Italy.

Northern Italy, in the early 19th century, came under the domination of the Kingdom of Sardinia, which besides its namesake island, also ruled the expansive Piedmont and Savoy regions along the French-Italian borderlands.

Up until the dissolution of the monarchy in 1946, the full titles of the Kings of the Kingdom of Italy (1861–1946) were: [Name], by the Grace of God and the will of the Nation, King of Italy, King of Sardinia, Cyprus, Jerusalem, Armenia, Duke of Savoy, count of Maurienne, Marquis (of the Holy Roman Empire) in Italy; Prince of Piedmont, Carignano, Oneglia, Poirino, Trino; Prince and Perpetual Vicar of the Holy Roman Empire; Prince of Carmagnola, Montmélian with Arbin and Francin, Prince bailiff of the Duchy of Aosta, Prince of Chieri, Dronero, Crescentino, Riva di Chieri and Banna, Busca, Bene, Bra, Duke of Genoa, Monferrat, Aosta, Duke of Chablais, Genevois, Duke of Piacenza, Marquis of Saluzzo (Saluces), Ivrea, Susa, of Maro, Oristano, Cesana, Savona, Tarantasia, Borgomanero and Cureggio, Caselle, Rivoli, Pianezza, Govone, Salussola, Racconigi over Tegerone, Migliabruna and Motturone, Cavallermaggiore, Marene, Modane and Lanslebourg, Livorno Ferraris, Santhià, Agliè, Centallo and Demonte, Desana, Ghemme, Vigone, Count of Barge, Villafranca, Ginevra, Nizza, Tenda, Romont, Asti, Alessandria, of Goceano, Novara, Tortona, Bobbio, Soissons, Sant'Antioco, Pollenzo, Roccabruna, Tricerro, Bairo, Ozegna, delle Apertole, Baron of Vaud and of Faucigni, Lord of Vercelli, Pinerolo, of Lomellina, of Valle Sesia, of the Marquisate of Ceva, Overlord of Monaco, Roccabruna and eleven-twelfths of Menton, Noble Patrician of Venice, Patrician of Ferrara.