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 2000 the population is 124,279. 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" . 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".