Fortified - or liqueur - wines, are wines to which alcohol, in the form of a spirit, has been added. They are also wines to which concentrated or cooked must has been added in order to increase their potential alcoholic content. So they are special wines, because they are not simply the result of fermenting grapes or must, but of an extra added ingredient. The most famous fortified wines include Port, Sherry, Madeira and Marsala. But fortified wine can be produced from a vast variety of wines; first and foremost, it can be a type of raisin wine.

Fortified wines can be either dry or sweet. If a spirit (or alcohol) is added after the wine has been fermented, a dry product is obtained. If, on the other hand, a spirit (or alcohol) is added during fermentation, this arrests the action of the yeasts, so that some of the unfermented sugars in the initial must are not converted. So the wine obtained may be more or less sweet. Finally, if cooked or concentrated must is added, the resulting product will be sweet.

The Sherry, produced in Andalusia (Spain) is normally dry. It is made by adding a wine-based spirit to a dry white wine and then ageing it in large wooden barrels. In contrast, Port, which is produced in Portugal, is normally sweet. It is obtained by adding a spirit to a fermenting red wine. The adding of the spirit arrests the fermentation, so that a part of the sugar remains unfermented, giving a sweet taste to the wine, which is then aged in large barrels. Marsala produced in Sicily can be either white or red, dry, medium-dry or sweet.