Bairro (lit. quarter, Portuguese pronunciation: [ˈbajʁu]) is a Portuguese word and refers to a community or region within a city or municipality. Bairros exist in the majority of large cities in the world. Related words in English include neighborhood, district, borough or subdivision. Bairro is cognate with the Germanic berg, burg, borg, burgh, borough, etc; and also the Spanish barrio, all of which descend from the same Proto-Indo European root.

In Brazil, the word applies to urban areas in cities, in which the bairros have a role only in localization, without any specific administrative function. Some cities' bairros have defined territorial limits, while most follow the popular definition among its citizens.

In Portugal, subdivisions in only a few densely-populated urban regions are called bairros, though these do not have any administrative power. An example is the Bairro Alto in Lisbon. Freguesia is the more common subdivision in Portugal.

In Mozambique, bairros are administrative subdivisions of urban districts with important functions in the identification of the residents and determine the attributes of the area in regards to construction or agriculture, much like zoning. They are directed by secretários.