Regions of Portugal

Administratively, Portugal is a unitary and decentralized State. Nonetheless, operationally, it is highly centralized system with administrative divisions organized into three tiers. The State is organized under the principles of subsidiarity, local government autonomy, and democratic decentralization of the public service.

The government structure is based on the 1976 Constitution, adopted after the 1975 Carnation Revolution. In addition to defining the status of the autonomous regions (Portuguese: regiões autónomas) Azores and Madeira (Articles 225-234), the Constitution specifically identifies the three tiers of government (Article 235-262): civil parishes (freguesias), municipalities (municípios) and administrative regions (regiões administrativas). In law 75/2013 of September 2013 the two types of administrative regions were defined: metropolitan areas (áreas metropolitanas) and intermunicipal communities (comunidades intermunicipais). Also, the powers and duties of the civil parishes, municipalities, metropolitan areas and intermunicipal communities were specified.

In addition, the Portuguese territory was redefined during European integration, under a system of statistical regions and subregions known as Nomenclature of Territorial Units for Statistics. These NUTS definitions, used for collecting statistical information, follow many of the countries border definitions. Although utilized by the Portuguese government, they do not have a legal status in law.

The division of the Portuguese territory is established in title eight (Título VIII) of the Portuguese constitution: granting local authority to territorial collectivities with representative organs to affect the interests of the local populations. These collectivities are defined as autonomous regions, administrative regions, municipalities and civil parishes, but reserves the right of urban areas and islands to establish other forms of local authority. In defining the rights and privileges of these entities, the constitution also defines sources of income, that includes local heritage, budgets and equalization transfers from the State, in addition to defining the basic role of local government at each level.

...
Wikipedia