Santa Margarita is a census-designated place located in San Luis Obispo County, California. It was founded in 1889 near Cuesta Peak and San Luis Obispo along State Route 58. The town's name comes from the Mexican Alta California land Grant. It is home to the Santa Margarita de Cortona Asistencia. The population was 1,259 at the 2010 census.
Located in the foothills of the Santa Lucia Mountains, it is one of the most rural areas in San Luis Obispo County. Santa Margarita Lake, a major water source for San Luis Obispo, is located several miles southeast of the town on the Salinas River. It is served by the zip code 93453 and area code 805.
According to the United States Census Bureau, the CDP covers an area of 0.5 square miles (1.3 km²), all of it land.