Port wine (also known as Vinho do Porto, [ˌviɲuduˈpoɾtu] , Porto, and usually simply port) is a Portuguese fortified wine produced exclusively in the Douro Valley in the northern provinces of Portugal.It is typically a sweet, red wine, often served as a dessert wine, though it also comes in dry, semi-dry, and white varieties.Fortified wines in the style of port are also produced outside Portugal, most notably in Australia, France, South Africa, Canada, India, Argentina, and the United States.he wine produced is then fortified by the addition of a neutral grape spirit known as aguardente in order to stop the fermentation, leaving residual sugar in the wine, and to boost the alcohol content.