The Duoro Valley cradles the Duoro River whose name comes from Rio do Ouro (River of Gold) and which has always been Porto’s lifeblood. The region has long been associated with port producing vineyards, and over the millennia, this otherworldly, ever-changing terrain has been sculptured by hard working wine growers. The sublime landscapes of neat rock terraces wrap around every precipitous hillside, and the whitewashed quintas, port producing estates, dot the valley. Traditionally, the wine was taken downriver in flat-bottom boats called rabelos, to be stored in barrels in cellars in Vila Nova de Gaia, just across the river from Porto. Further upstream, the Duoro River, the third-longest in the Iberian Peninsula (after the Tagus and Ebro) forms a natural border between Spain and Portugal for 70 miles of narrow canyons. Historically, it formed a barrier to invasions, creating a cultural and linguistic divide. Recently, fifteen dams have been built on the Douro to regulate the water flow, generate hydroelectric power, and allow navigation through locks.

The port wine-producing Douro Valley region is the third oldest protected wine region in the world after the Tokaj region in Hungary, established in 1730, and Chianti, in 1716. In 1756, during the rule of the Marquis of Pombal, the Companhia Geral da Agricultura das Vinhas do Alto Douro was founded to guarantee the quality of the product and fair pricing to the consumer. After the Methuen Treaty of 1703, port became very popular in England, when merchants were permitted to import it at a low duty, while war with France deprived English wine drinkers of French wine. British importers could be credited for recognizing that a smooth, already fortified wine that would appeal to English palates would survive the trip to London. In 1678, a Liverpool wine merchant sent two new representatives to Viana do Castelo, north of Oporto, to learn the wine trade. While on a vacation in the Douro, the two gentlemen visited the Abbot of Lamego, who treated them to a "very agreeable, sweetish and extremely smooth" wine," which had been fortified with a distilled spirit. The two Englishmen were so pleased with the product that they purchased the Abbot's entire lot and shipped it home. The continued British involvement in the port trade can be seen in the names of many port Shippers and brands: Broadbent, Cockburn, Croft, Dow, Gould Campbell, Graham, Osborne, Offley, Sandeman, Taylor, and Warre being amongst the best known. The British involvement grew so strong that they formed a trade association that became a gentlemen's club.

Port can only be 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 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 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. Touriga Nacional is widely considered to be the most desirable port grape but the difficulty in growing it and the small yields make Touriga Francesa the most widely planted grape. While a few shippers have experimented with Ports produced from a single variety of grapes, all Ports commercially available are from a blend of different grapes. Grapes grown for port are generally characterized by their small, dense fruit which produce concentrated and long-lasting flavors, suitable for long ageing. Port wine is typically richer, sweeter, heavier, and higher in alcohol content than unfortified wines, and usually has 19% to 20% alcohol content. Port is commonly served after meals as a dessert wine in English-speaking countries, often with cheese, nuts, and/or chocolate; white and tawny ports are often served as an apéritif. In Europe all types of port are frequently consumed as aperitifs.