Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2007, the population was 248,096. The county seat is San Rafael and the largest employer is the county government.

Marin County is well known for its natural beauty, liberal politics, affluence and a strong New Age reputation. In May 2009, the county had the fifth highest income per capita in the United States at $91,483. The county is governed by local cities and the Marin County Board of Supervisors.San Quentin Prison is located in the county, as is Skywalker Ranch. Autodesk, the publisher of AutoCAD, is also located there, as well as numerous other high-tech companies. The headquarters of film and media company Lucasfilm Ltd., previously based in San Rafael, have moved to the Presidio of San Francisco.