Larkspur is a city in Marin County, California, United States. Larkspur is located 3 miles south of San Rafael, at an elevation of 43 feet. As of the 2020 census, the city's population was 13,064. Larkspur's Police Department is shared with that of the neighboring Corte Madera and town of San Anselmo as the Central Marin Police Authority. The city's main thoroughfare is Magnolia Avenue, which runs through the Larkspur Downtown Historic District.