Larkfield-Wikiup is a census-designated place unincorporated area in Sonoma County, California, United States. The population was 8,884 at the 2010 census, up from 7,479 at the 2000 census. It comprises the Mark West area between Santa Rosa, Windsor, Calistoga, and Fulton. There are at least four schools within the limits of the CDP, including Cardinal Newman High School, John B. Riebli Elementary School, Mark West Elementary, and San Miguel Elementary schools.