Otay Mesa is a community in the southern exclave of the city of San Diego, just north of the U.S.–Mexico border.

South San Diego is a district within the City of San Diego, and is in the larger South Bay region of southwestern San Diego County, California. South San Diego is a practical exclave of San Diego, having no land connection with the rest of the city. It is the only part of the city which borders Mexico. South San Diego includes four of the city's official community planning areas: Otay Mesa, Otay Mesa-Nestor, San Ysidro, and the Tijuana River Valley.