Dillon Beach is a census-designated place (CDP) in Marin County, California, United States. Dillon Beach is located 3.25 miles (5.2 km) west of Tomales, at an elevation of 89 feet (27 m). The population was 319 at the 2000 census. Dillon Beach was named after the founder, George Dillon, who settled there in 1858.