A viceroyalty was an entity headed by a viceroy. It dates back to the Spanish colonization of the Americas in the sixteenth century.

In the scope of the Portuguese Empire, the term "Viceroyalty of Brazil" is also occasionally used to designate the colonial State of Brazil, in the historic period while its governors had the title of "Viceroy". Some of the governors of Portuguese India were also called "Viceroy".

The viceroyalty (Spanish: virreinato) was a local, political, social, and administrative institution, created by the Spanish monarchy in the sixteenth century, for ruling its overseas territories.

The administration over the vast territories of the Spanish Empire was carried out by viceroys, who became governors of an area, which was considered not as a colony but as a province of the empire, with the same rights as any other province in Peninsular Spain.

According to the lawyer Fernando de Trazegnies, the status of the Viceroyalties was like that of a Kingdom among the Kingdoms of the Indies, and that the fact that legal Pluralism was practiced in Derecho Indiano would be sufficient proof that the Crown did not seek to practice a Exploitative colonialism (where local institutions, which protect the socioeconomic rights of the Vassal people, are ignored, under the excuse of the Right of Conquest), if not political integration into the Hispanic Monarchy in the same plural way that had already been done with the rest of its territories in Europe, based on the characteristic Fueros of the traditional and composite Monarchy that maintained the regional laws of each nation integrated into the Spanish Monarchy (and that was even practiced within peninsular Spain after the Reconquista, such as the Fueros of Aragón or the Fueros of Navarra). This would be evidenced by the creation of the República de Indios in which the political traditions of indigenous customary law would remain alive as a state within the several states that made up the Composite Monarchy, or the desire of the Spanish conquistadors to make pacts with the Natural Lords of the new lands (indigenous nobility and chiefs) to legitimize the conquest in natural law and integrate them into the seigneurial system, respecting the sovereignty of the natives and their ethnic lordships, which could not be deprived of their rights and was only possible its annexation to the Spanish Empire through alliance pacts (whose conditions of such pacts had to include the part of the indigenous sovereign, protector of the common Indian).

"However, although there was only one Crown, the diversity of the kingdoms was maintained, with their own jurisdictions, with their national law. So, when taking possession of America, the Crown of Castile proceeded in a similar way as in Spain for manage diversity; and this is how he recognizes two great kingdoms: that of New Spain (today Mexico) and that of New Castilla (today Peru). And his first reaction is to govern them in the same plural form as in Spain, that is, integrating local customs and authorities within a larger political perspective represented by the Crown of Castile (...) aims to create two “republics” under the same Crown: the “republic of Spaniards” and the “republic of Indians”, each with their own authorities and rules, although both subject to the mandates of the Crown. As it was evident that the Spanish King could not personally govern such distant towns and territories, he established that such kingdoms are Viceroyalties, that is, political spaces with their own identity that are in charge of a personal representative of the Monarch, who was the Viceroy. This was not an oppressive political form that placed the people governed by the Viceroy in inferior conditions. Nor is it an invention specially designed to subdue the American Indians. Viceroyalties exist in Europe and the Spanish Crown itself has governed some of the different Hispanic kingdoms in this way; Thus, Valencia and Naples were viceroyalties of Aragon and, after the annexation of Navarre to the Crown of Castile, it remained as a viceroyalty (...) It is not surprising then that this new dynasty, known as the Austrias, used a pluralistic imperial model also to annex the new lands of America. On the other hand, the Papal Bull itself, which granted the Catholic Monarchs the dominion of these new lands, established the Supreme and Universal Principality for the Crown of Castile, but did not deprive the kings and natural lords of the Indies of their lordships."

— Fernando de Trazegnies

At the same time, the Spanish Empire itself and the Council of the Indies did not perceive the American Viceroyalties as possessions analogous to the Factories or administrative Colonies, in the style of other empires with a more Mercantilist behavior towards the Natives of their non-European possessions, but rather perceived the Viceroyalties as overseas Provinces, with rights equivalent in hierarchy to those of the rest of the provinces of the Crown of Castile (according to the Laws of the Indies), of which they were an integral part. Even the word colony would not have been used in any legal document of the Spanish Monarchy with respect to the Indies until the 17th century, and after the arrival of the Bourbons it would be used in reference to its classic etymological sense of human settlements established in new territories, and not in the modern sense with connotations of economic exploitation.