As in other European countries, the institutions of the Neapolitan monarchy were the result of a process of stratification which had taken centuries, leading to a progressive growth of the administrative apparatus, which tended to become specialised. The fundamental elements of the administrative structure of the Neapolitan state in fact remained almost unchanged until the so-called ‘French decade’ (1806–15), when it was radically transformed on the model of the Napoleonic state. Its foundations dated back to the Aragonese period (1442–1503), when the composition and the competence of the various authorities were defined. At the centre of the system was the Sacro Regio Consiglio, the highest advisory body, with broad judiciary powers. Another high advisory body, for questions involving finance, was the Regia Camera della Sommaria. It had jurisdiction over all cases involving the royal finances, and over disputes involving the baroni (feudal lords) or the università (local communities). The Gran Corte della Vicaria had civil and criminal jurisdiction, and control of law and order in the capital. The administration in the outlying areas was organised around the Udienze (local authorities), whose functions were not only judicial, but also involved the general government of their particular provinces. The Sommaria had provincial offices which collected taxes and revenues.

The principal transformation introduced by the Spanish system of government (1503–1707) was the absence of a sovereign in Naples and the consequent institution of the Viceroy.