Tijuana, is the largest city of the Mexican state of Baja California, situated on the U.S.-Mexico border adjacent to its sister city of San Diego, California. Tijuana is the westernmost city in Mexico, though the westernmost population center is located in Isla Guadalupe. Tijuana is considered by the Mexican government to be the dominant regional center in northwestern Mexico.

According to the 2005 census, the Tijuana metropolitan area was the sixth-largest in Mexico, with a population of 1,483,992, and one of the fastest growing cities in Mexico. Tijuana forms part of the San Diego-Tijuana Metropolitan Area, the total population of which has been estimated to be just over 5 million in 2009, making it the 22nd largest metropolitan area in the Americas and the largest bi-national metropolitan area that is shared between US and Mexico. It is estimated that the two border crossings in Tijuana account for 300,000 daily border crossings.