The Greater Metropolitan Area of Porto (Portuguese:Grande Área Metropolitana do Porto) is a metropolitan area in coastal northern Portugal which covers 16 municipalities, including the City of Porto, making up the second biggest urban area in the country. The Greater Metropolitan Area of Porto is a union of metropolitan municipalities (Grande Área Metropolitana), comprising both Grande Porto Subregion and Entre Douro e Vouga Subregion which are two NUTS III subdivisions. The first has 11 municipalities and the second is only five. It covers 1883,61 km² and had a 2011 population of 1,676,848. Currently the most populous municipality is Vila Nova de Gaia, which is located on the South side of the Douro River, in the opposite side of Porto.

The original Metropolitan Area of Oporto was constituted by nine municipalities: Oporto (the capital), Espinho, Gondomar, Maia, Matosinhos, Póvoa de Varzim, Vila Nova de Gaia, Valongo, and Vila do Conde. The process of enlargement to Santa Maria da Feira, Santo Tirso, Trofa, Arouca and São João da Madeira was approved in the Porto Metropolitan Assembly on January 8, 2005, and started being known as Grande Área Metropolitana do Porto (Greater metropolitan Area of Porto). At September, 1st 2008 Oliveira de Azeméis and Vale de Cambra joined and it became a group of 16 municipalities.

The term metropolitan area refers to a region consisting of a densely populated urban core and its less-populated surrounding territories, sharing industry, infrastructure, and housing. A metropolitan area usually comprises multiple jurisdictions and municipalities: neighborhoods, townships, cities, exurbs, counties, and even states. As social, economic and political institutions have changed, metropolitan areas have become key economic and political regions.

A metropolitan area combines an urban agglomeration (the contiguous, built-up area) with zones not necessarily urban in character, but closely bound to the center by employment or other commerce. These outlying zones are sometimes known as a commuter belt, and may extend well beyond the urban zone, to other political entities. For example, El Monte, California is considered part of the Los Angeles' metro area.

In practice, the parameters of metropolitan areas, in both official and unofficial usage, are not consistent. Sometimes they are little different from an urban area, and in other cases they cover broad regions that have little relation to a single urban settlement; comparative statistics for metropolitan area should take this into account. Population figures given for one metro area can vary by millions, and there is a tendency for people to promote the highest figure available for their own "city". However the most ambitious metropolitan area population figures are often better seen as the population of a "metropolitan region" than of a "city".^{[citation needed]}