Muir Beach is a census designated place, unincorporated community, and beach on the Pacific Ocean. The community is located 16.5 miles northwest of San Francisco in western Marin County, California, United States. Unlike many other entities in the area, it is not named directly in honor of conservationist John Muir; instead, it was named after Muir Woods National Monument to capitalize on the latter's popularity. The population was 304 at the 2020 census.