A monopole (‘monopoly’ in French) is a vineyard area controlled by a single winery (or wine company) and can be as small as a designated vineyard (select number of rows) or as large as an entire AOC. The Napoleonic inheritance laws typically caused vineyards to be so finely divided that négociants are needed to bottle commercial quantities of a wine. Whether a monopole indicates a wine of unusual quality or not is a matter of much debate.
Example of Monopoles: (in Burgundy)
Romanée-Conti and La Tâche - (Domaine de la Romanée-Conti).
A monopole wine is a wine produced from the grapes of a single vineyard with that vineyard's name appearing on the wine label.

 

Throughout the history of winemaking and viticulture, the differences in quality between one plot of land and another have been observed with the boundaries of these vineyards well demarcated. In Burgundy, the vineyards of the area are classified with the highest quality vineyards receiving the ranking of Grand cru. The names of these vineyards will often appear on the wine label of Burgundy wines in bolder, more prominent print than even the name of the producer.
Monopole wines are usually pricier than multi-vineyard wines, and are typically produced in limited quantities. Naming the vineyard on the label lets buyers know that the wine inside the bottle was made from special fruit that possesses certain unique characteristics.
Though some monopole wines are named for properties owned by the wineries themselves, many of the best vineyards are owned by independent growers who don't produce any wine of their own. Instead, they grow grapes on behalf of winery clients, who pay growers by the ton or by the acre for their fruit.
Grapes from top winegrowers are usually in great demand, which allows them to charge top dollar for their grapes. Are monopole wines better than non-designated wines? Only if you prefer the characteristics of the fruit and resulting wine that comes from those particular vineyard sites.