Barsac is a small village about 65 kilometres (40 miles) south of Bordeaux, in the southwest of France. It makes sweet white wines based on the Semillon grape variety.

These are some of the finest wines of their type on Earth. Among the most prominent properties are the Châteaux Climens, Coutet and Doisy Daëne. However, Barsac is less well known overall than the Sauternes appellation within whose borders the zone lies. Vineyard surface area totals 390 hectares (964 acres).

Semillon accounts for about eight in every 10 vines in the local vineyards. Sauvignon Blanc accounts for most of the remaining vineyard area, with smaller amounts Muscadelle and Sauvignon Gris. Semillon gives the wines a broad richness and structure, plus aromas of beeswax, tropical fruit and apricot. Sauvignon Blanc contributes herbal and vegetal aromatics. It also brings sufficient acidity to keep the wines fresh rather than cloying.

The chateau owners and grape growers of Barsac have a unique privilege. They have their very own Barsac appellation, but may also claim the Sauternes title for their wines. Of the four villages that make up the Sauternes AOC viticultural area with Sauternes itself, only Barsac has this honour. (Bommes, Fargues and Preignac are the other three).

The appellation laws for Sauternes and Barsac are identical in all but the territory they cover. In both cases the grapes may be picked - by hand - only when their must weight reaches 221 grams per litre. The same stipulation for the area's dry white wines is just 162g/l.

There are a few subtle differences between Barsac and other parts of the broader Sauternes region. Sauternes village is slightly hillier, which increases the effects of the mists and ultimately leads to more richly botrytised wines. Barsac's flatter sand and limestone based soils create finer, more elegantly flavoured wines.

Barsac's eastern border is formed by the Garonne in the northern half of the zone. Its tributary the Ciron river does the same in the southern half.

This confluence of a smaller, faster running, cooler river with a larger one is a key factor in creating morning mists. These are closely associated with botrytis cinerea (noble rot) formation. Loupiac sits on the other side of the Garonne.