Rancho San Diego is a census-designated place (CDP) located in the East County region of San Diego County, California, in the United States. It serves as a residential community within the broader metropolitan area.
The area began its development as subdivisions starting in the 1970s. According to the 2020 census, Rancho San Diego had a population of 21,858, reflecting a slight increase from the 21,208 residents recorded in the 2010 census.