Chablis lies near the world’s northerly limits for successful viticulture, and is actually closer to Champagne’s Aube region than the Côte d’Or. The town itself lies almost halfway between Paris and Beaune in the Serein ("serene") River Valley, a conduit for cold winds and frost (a chief worry for vignerons in the springtime). In the region's cool continental climate, three AOPs—Petit Chablis, Chablis, and Chablis Grand Cru—produce only white wines, made exclusively from Chardonnay. From the development of the original AOC boundaries in the 1930s through five ensuing decades of appellation changes and expansion, soil character remained at the center of the discussion. The better vineyards in the region—including most graded as Chablis AOP, all 40 premiers crus and the entirety of Chablis Grand Cru AOP—are located in areas atop Kimmeridgian marl. A mixture of limestone and clay laced with millions of oyster fossils, Kimmeridgian marl is visible in hillside outcrops around the village of Chablis, and soils derived from it are believed to produce higher quality wines. On the elevated plateaus above the hillsides Kimmeridgian marl is buried under Portlandien limestone, a younger rock strata and a purer form of limestone. Petit Chablis, typically the simplest wine, is produced from these cooler, wind-exposed sites situated on Portlandien limestone.
Chablis itself is Burgundy’s largest white winegrowing region, and one out of five bottles of Burgundy annually bear its name on the label. The village wines are actually produced from 17 different communes, and Chablis' 40 premier cru geographic designations, further grouped into 17 "major" premiers crus, are located on hillsides on both "right" and "left" banks of the Serein. Top premier crus on the right bank include Montée de Tonnerre and Fourchaume; on the left, Vaillons and Montmains. There is technically only one grand cru appellation in Chablis, comprising the southwest-facing slopes just north of the town itself, but the Chablis Grand Cru AOP has seven geographic designations: Les Clos, Vaudésir, Valmur, Preuses, Blanchot, Bougros, and Grenouilles. (An eighth parcel, La Moutonne—a monopole of Domaine Long-Depaquit overlapping Vaudésir and Preuses—is permitted by the INAO for usage on labels but not listed as an official geographic designation.)
The benchmark style for Chablis is often exemplified at the premier cru level: classic examples show pronounced acidity, medium weight, lees character, and an intensely mineral, steely character unencumbered by new oak. Only at the grand cru level, where the wines are richer and riper, does significant new oak begin to enter the equation. Yet even with top wines some producers, convinced that the influence of wood compromises the classic expression of Chablis, prefer to ferment and age wines solely in stainless steel. Whether grand or premier cru, the finest Chablis wines are austere in their youth but rewarding with age. Classic descriptors include hazelnuts, oyster shells and lemon. Beyond Chablis, there are two other communal appellations in the Yonne département: Irancy AOP, a red wine appellation for light, Pinot Noir-based reds, and St-Bris AOP, the only Sauvignon Blanc appellation in Burgundy.