Port wine (also known as vinho do Porto, ˌviɲu ðuˈpoɾtu, or simply port) is a Portuguese fortified wine produced in the Douro Valley of northern Portugal. It is typically a sweet red wine, often served with dessert, although it also comes in dry, semi-dry, and white varieties.
Other port-style fortified wines are produced outside Portugal - in Argentina, Australia, Canada, France, India, South Africa, Spain, and the United States - but under the European Union Protected Designation of Origin guidelines, only wines from Portugal are allowed to be labelled "port".
Port is produced from grapes grown and processed in the demarcated Douro region. The wine produced is then fortified by the addition of a neutral grape spirit known as aguardente to stop the fermentation, leaving residual sugar in the wine, and to boost the alcohol content. The fortification spirit is sometimes referred to as brandy, but it bears little resemblance to commercial brandies. The wine is then stored and aged, often in barrels stored in a lodge (meaning "cellar") as is the case in Vila Nova de Gaia, before being bottled. The wine received its name, "port", in the latter half of the 17th century from the seaport city of Porto at the mouth of the Douro River, where much of the product was brought to market or for export to other countries in Europe. The Douro valley where port wine is produced was defined and established as a protected region, and the name Douro thus an official appellation, in 1756, making it the third oldest wine after Chianti (1716) and Tokaj (1730).
The reaches of the valley of the Douro River in northern Portugal have a microclimate that is optimal for cultivation of olives, almonds, and especially grapes important for making port wine. The region around Pinhão and São João da Pesqueira is considered to be the centre of port production, and is known for its picturesque quintas – estates clinging on to almost vertical slopes dropping down to the river.
The demarcation of the Douro River Valley includes a broad swath of land of pre-Cambrian schist and granite.