Santa Rosa is the county seat of Sonoma County, California, United States. As of April 2010, the population of Santa Rosa was approximately 167,396 residents. Santa Rosa is the largest city in California's Wine Country and fifth largest city in the San Francisco Bay Area, after San Jose, San Francisco, Oakland, and Fremont.

Santa Rosa's metropolitan statistical area has a population of 486,630, making it the 12th largest in California and the 105th largest in the United States.