Opus One Winery is a winery in Oakville, California, United States. The wine was called napamedoc until 1982 when it was named Opus One. The winery was founded as a joint venture between Baron Philippe de Rothschild of Château Mouton Rothschild and Robert Mondavi to create a single Bordeaux style blend based upon Napa Valley Cabernet Sauvignon. It is located across State Route 29 from the Robert Mondavi Winery. The creation of this winery venture in 1980 was big news in the wine industry; de Rothschild's involvement added an air of respectability to the burgeoning Napa wine region. The first vintage, 1979 was released in 1984 at the same time as the 1980 vintage. For a while it was the most expensive Californian wine, and to date still ranks among the most expensive red wines produced in the Napa Valley, with the 2014 vintage retailing for $325 per bottle. In 1989 a new winery was built just down the road, the first vintage from the new winery was from 1991 and was released in 1994.

Second wine or second label is a term commonly associated with Bordeaux wine to refer to a second label wine made from cuvee not selected for use in the Grand vin or first label. In some cases a third wine or even fourth wine is also produced. Depending on the house winemaking style, individual plots of a vineyard may be selected, often those of the youngest vines, and fermented separately, with the best performing barrels being chosen for the house's top wine and the other barrels being bottled under a separate label and sold for a lower price than the Grand vin.