Guenoc Valley is an American Viticultural Area in Lake County, California, United States, about 15 mi (24 km) north of the town of Calistoga.
Guenoc Valley also experiences slightly greater seasonal temperature extremes, being warmer in the summer and colder in the winter.
For these reasons, the United States Department of the Treasury Alcohol and Tobacco Tax and Trade Bureau determined that Guenoc Valley possesses geographical features which distinguish the area viticulturally.
The winery and the 21,000 acres (8,500 ha) it sits on was owned by Malulani Investments Ltd., a real estate group that since 1964 had been the only shareholder and stockholder of Guenoc.
The area also has very cool nights, preserving acidity and producing rich wines with elegant structure, making it a Climate Region III.