The recorded history of the San Diego, California, region began in the present state of California when San Diego Bay was first discovered by Europeans. San Diego was the first part of California that Europeans settled in, so that San Diego has been described as "the birthplace of California."

Native Americans such as the Kumeyaay people had been living in the area for as long as 12,000 years. Explorer Juan Rodriguez Cabrillo discovered San Diego Bay in 1542, but it was 200 years before Europeans settled the area. A fort and mission were established in 1769, which gradually expanded into a settlement under first Spanish and then Mexican rule.

San Diego became part of the U.S. in 1848, and the town was named the county seat of San Diego County when California was granted statehood in 1850. It remained a very small town for several decades, but grew rapidly after 1880 due to development and the establishment of multiple military facilities. Growth was especially rapid during and immediately after World War II. Entrepreneurs and boosters laid the basis for an economy based today on the military, defense industries, tourism, international trade, and manufacturing. San Diego is now the eighth largest city in the country and forms the heart of the larger San Diego metropolitan area.