Napa Valley subregions are the nested American Viticultural Areas within the larger Napa Valley AVA, created to recognize meaningful differences in climate, elevation, soils, exposure, and local growing conditions. These include well-known names such as Howell Mountain, Mount Veeder, Rutherford, Oakville, Stags Leap District, Calistoga, Coombsville, Los Carneros, and other legally defined appellations.
Their importance lies in showing that Napa is not a single uniform wine style, even though Cabernet Sauvignon dominates its reputation. Valley-floor sites often emphasize ripeness, fruit density, and polished structure, while mountain and hillside AVAs can produce wines of firmer tannin, greater concentration, and stronger site expression.