Tannat is a red wine grape, historically grown at the foothills of the Pyrenees Mountains in southwestern France in the Madiran AOC, having been grown in that region since the 17th and 18th centuries. It is also grown in Uruguay, Argentina, Australia, Brazil, Peru, and in Italy's Puglia region where it is used as a blending grape.

Tannat wines produced in Uruguay are usually quite different in character from Madiran wines, being lighter in body and lower in tannins. It is also used to make Armagnac and full bodied rose wine. In France, efforts to solve the harsh tannic nature of the grape lead to the development of the winemaking technique known as micro-oxygenation, by the Madiran winemaker Patrick Ducournau.

Tannat is notable for its very high tannin levels and is often blended with Cabernet Sauvignon, Cabernet Franc to soften the astringency and make them more approachable. A French Tannat wine is characterized by its firm, tannic structure with smoke and plum aromas, a spicy finish and the ability to age well.

French kings accepted Madiran wines as payment for taxes. Madiran appellation laws mandate that Tannat be blended with Cabernet Sauvignon or Cabernet Franc, but producers have recently begun receiving notable press for their 100% Tannat Madiran wines.

Tannat continues to be grown in the Basque country, most notably in the tiny appellation of Irouleguy, on the Spanish border. In 1870, Basque immigrants took the grape to Uruguay, where it adapted perfectly well. Today it is often blended with Pinot Noir and Merlot and is made in a variety of styles including those reminiscent of Port and Beaujolais.

From Uruguay the vine spread to Argentina and from there flying winemakers promoted the grape's resurgence in California at the end of the 20th century. It has since become the national red grape variety of Uruguay, accounting for approximately one third of all wine produced in that country; more Tannat is grown in Uruguay than in the varietal's native France.