Louis-Gaspard d'Estournel began to build the estate in 1791. Sixty-four years later, the 1855 classification ranked Cos d'Estournel a second growth, among the first of the Saint-Estèphe appellation. Michel Reybier bought the estate in 2000. Saint-Estèphe lies on gravel over clay and marine limestone, and Cos is one of its five classified growths.

The vineyard covers 100 hectares, two-thirds Cabernet Sauvignon with Merlot and a little Cabernet Franc and Petit Verdot. The vines average 45 years, and those kept for the grand vin 55. The estate replants by massal selection from its own old vines. In 2003 it introduced cone-shaped stainless steel vats, and since 2008 the wine has been made in a gravity-flow cellar, without pumping.

The bottles here are mostly older vintages of the grand vin, going back to 1955, which Saint-Estèphe builds for long keeping. See also Pauillac next door, the collector wines or the full range of Bordeaux wines.