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 the name of 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, is mostly populated with people of European descent, mainly Italian and Spanish. In contrast, inland Argentina, especially the Northwest, has had less European immigration and retains more white criollos, mestizos and indians. For that reason, the inhabitants of Buenos Aires tend to consider themselves as different from the people of inland Argentina and more akin to the inhabitants of Montevideo, the capital city of Uruguay, which has a similar history of European immigration.

In Chile porteño/a is commonly used for residents of Valparaíso.