Tomales Bay State Park is a California state park in Marin County, California. It consists of approximately 2,000 acres (8 km²) divided between two areas, one on the west side of Tomales Bay and the other on the east side. The main area, on the west, is part of the Point Reyes peninsula, and adjacent to Point Reyes National Seashore, which is operated by the U.S. National Park Service.