Napa County is a county located north of the San Francisco Bay Area in the U.S. state of California. It is coterminous with the Napa, California, Metropolitan Statistical Area. As of 2010 the population is 136,484. The county seat is Napa. Napa County was one of the original counties of California, created in 1850 at the time of statehood. Parts of the county's territory were given to Lake County in 1861. The word napa is of Native American derivation and has been variously translated as "grizzly bear", "house", "motherland", and "fish"^{[citation needed]}. Of the many explanations of the name's origin, the most plausible seems to be that it is derived from the Patwin word napo meaning house^{[citation needed]}, although local residents will often cite an urban legend that gives the translation as "you will always return".

Napa County, once the producer of many different crops, is known today for its wine industry, rising in the 1960s to the first rank of wine regions with France, Italy, and Spain.^{[citation needed]}