San Diego–Tijuana is an
international metropolitan conurbation, straddling the border of the adjacent
North American coastal cities of
San Diego,
California, United States and
Tijuana,
Baja California,
Mexico. The 2012 population of the region was 4,922,723, making it the largest
bi-national conurbation shared between the United States and Mexico, the second-largest shared between the US and another country (after
Detroit-Windsor), and the fourth largest in the world. In its entirety, the region consists of
San Diego County in the United States and the
municipalities of
Tijuana,
Rosarito Beach, and
Tecate in Mexico. It is the third most populous region in the California-Baja California region, smaller only than the metropolitan areas of
Greater Los Angeles and the
San Francisco Bay Area.