Stockton is a city in and the county seat of San Joaquin County in the Central Valley of the U.S. state of California. It is the most populous city in the county, the 11th-most populous city in California and the 60th-most populous city in the United States. Stockton's population in 2020 was 320,804. It was named an All-America City in 1999, 2004, 2015, and again in 2017 and 2018. The city is located on the San Joaquin River in the northern San Joaquin Valley. It lies at the southeastern corner of a large inland river delta that isolates it from other nearby cities such as Sacramento and those of the San Francisco Bay Area.

Stockton was founded by Charles Maria Weber in 1849 after he acquired Rancho Campo de los Franceses. The city is named after Robert F. Stockton, and it was the first community in California to have a name not of Spanish or Native American origin.

Built during the California Gold Rush, Stockton's seaport serves as a gateway to the Central Valley and beyond. It provided easy access for trade and transportation to the southern gold mines. The University of the Pacific (UOP), chartered in 1851, is the oldest university in California, and has been located in Stockton since 1923. In 2012, Stockton filed for what was then the largest municipal bankruptcy in US history – which had multiple causes, including financial mismanagement in the 1990s, generous fringe benefits to unionized city employees, and the 2008 financial crisis. Stockton successfully exited bankruptcy in February 2015.