Porteño (feminine: porteña) in Spanish is used to refer to a person who is from or lives in a port city, but it can also be used as an adjective for anything related to those port cities.
The largest city to which the term is commonly applied is Buenos Aires, Argentina, and since the end of the 19th century Porteños has come to be a name (or demonym) for the people from that city. As a result of great immigration waves from Europe peaking in the 1880s, the Río de la Plata area, and in particular Buenos Aires and Montevideo, are mostly populated with people of European descent, mainly Italian, Spanish and German. In contrast, inland Argentina, especially the Northwest, has had less post-colonial European immigration and thus retains a population with a pre-colonial composition consisting of whites of criollo (colonial Spanish) ancestry, mestizos, and indigenous people.
In Chile, porteño/a is commonly used for residents of Valparaíso.
In Costa Rica, porteño/a is commonly used for people from the province of Puntarenas in the Pacific Coast.