Grand Cru is a French wine-term that refers to - ('great growth' or 'great classed growth') - and also a regional wine classification that designates a vineyard known for its historical reputation for consistently producing exceptional wine.
Although the term is often used to describe grapes, wine and even Cognac. The term is not technically a classification of wine quality per-se, but is intended to indicate the potential of the vineyard or terroir. It is the highest level of classification of AOP wines from Burgundy, Chablis and Alsace.
The same term is applied to Châteaux in Saint-Emilion (right bank of Bordeaux), although in this region it has a different meaning and does not represent the top tier of classification.

 

In Burgundy - the level immediately below 'Grand Cru' is known as 'Premier Cru', sometimes written as 1er cru. Early Burgundian wine history is distinctly marked by the work of the Cistercian Monks with the Catholic Church being the principal vineyard owner for most of the Middle Ages. Receiving land and vineyards as payment, endowments and as exchanges for indulgences the monks were able to studiously observe the quality of wine from individual plots and over time began to isolate those areas that would consistently produce wine of similar aroma, colour, body and vigour and designate them as Crus.

Following the success of the Bordeaux Wine Official Classification of 1855, Jules Lavalle developed an informal classification of vineyards of the Cote d'Or - Burgundy, in his book 'History and Statistics of the Cote d'Or'. In 1861, Lavalle's classification was formalized by the Beaune Committee of Agriculture. The designations of Grand Cru and Premier Cru were later developed and expanded on in the 1930's with the creation of the 'Appellation d'Origine Controlee' (or AOC) system, which is now known as AOP.