Sancerre is a renowned AOP wine produced in the surrounding area of the town Sancerre in the eastern Loire Valley, around 200 kms south of Paris - France. Almost all of the appellation lies on the left bank of the Loire River, opposite the AOP Pouilly-Fumé.
Sancerre is arguably the spiritual home of Sauvignon Blanc, though Pinot Noir is also grown, making up around 20% of the region's production, typically made is an early drinking style under the designation of Sancerre Rouge. A Rosé style wine from Pinot Noir is also produced in a unique vibrant style.
Though when you mention Sancerre - most think foremost about white wines - one of the original AOCs awarded in 1936, with their designation for red wines on 23 January 1959.

 

The AOC / AOP area has expanded greatly over the years, with a large area being designated in early 1998. A series of small valleys cut through the chalk hills, each with their own soil profiles, micro-climate and terroir. In the east are the flint soils that make mineral, long-lived wines. Between the town and Verdigny the soil consists of marl and gravel 'les caillottes' producing fruit driven, well balanced wines. And in the southwest, away from the river towards Menetou-Salon, the chalky 'terres blanches' (white ground) produce fuller wines.
As a cool continental climate wine region, one of the main viticultural threats in Sancerre is springtime frost. Throughout most of the growing season the nearby Loire River to the east and forest areas to the west help moderate temperatures. Herbaceous styles of Sauvignon Blanc are more common with large, leafy canopies, while producers wishing to minimize these qualities may use wide, open canopies.
Vine age can also contribute to how much grassy / herbaceous characters the resultant wine may have - as well as how early the grapes are harvested. The focus of Sancerre winemakers is usually to express the pure fruit flavours of Sauvignon Blanc and the natural terroir of the region with very little adjustments taking place in the winery during winemaking - with most of the wines in Sancerre being produced in a dry style and unoaked.