The territory belonging to the former Kingdom of the Two Sicilies until the eleventh century was under the nominal sovereignty of the Byzantine Empire, with the exception of the Duchy of Benevento and of Sicily, that fell under Arab rule in the ninth century. In reality, it enjoyed broad autonomy and was divided into a number of dukedoms.
In the second millennium, the most important historical stages are:
- The constitution in autonomous realm, although formally a vassal of the Church, under the dynasty of Altavilla that, following a process of conquest that begun in Melfi in 1043, obtained the real crown in 1130 and held it until 1194, when the male line was extinct. The crown was inherited, through Constance, last of Altavilla, from her son, the Emperor Frederick II.
- In 1266 the kingdom was conquered by Charles of Anjou, brother of King Louis IX of France; following the revolt of the Sicilian Vespers the kingdom was divided into a mainland under the Angevin dynasty, while Sicily was incorporated in the Kingdom of Aragona (Treaty of Caltabellotta, 1302).
- In 1442 Alfonso of Aragon defeated the Angevins and unified again the kingdom, uniting in fact with the Kingdom of Aragon in a Mediterranean kingdom with capital cities in Naples and Barcelona. Albeit with ups and downs, the kingdom was united all’Aragona until 1504.
- From 1504 to 1713, due to the unification of Castile and Aragon and the birth of the Kingdom of Spain, the Kingdom of Naples and the kingdom of Sicily were governed as Viceroyalties and actually joined the Kingdom of Spain. Philip II declared Napoli’s second largest city of the Kingdom after Madrid.
- In 1713, following the War of the Spanish Succession, the Kingdom of Naples was given to the Habsburgs and Sicily to the House of Savoy. Both have been short-term assignments: in 1734 Charles III recovered the crowns of Naples and Sicily and formed two independent kingdoms under personal union. From the geopolitical point of view, the events of the eighteenth century can be summed up in a struggle for dominance in Europe between the Habsburgs and the Bourbons, with England at times as a spectator, other times as a driver of the conflict.
- After the French Revolution, the Kingom was conquered by the French Empire. After the short reigns of Joseph Bonaparte and Joachim Murat, the Bourbons returned to the throne; the Kingdom was unified as the Kingdom of the Two Sicilies and Sicily lost its autonomy. On this occasion the King Ferdinand IV of Naples and III of Sicily changed its name to Ferdinand I of the Two Sicilies.