The University of California, San Diego (also referred to as UC San Diego or UCSD) is a public research university located in the La Jolla neighborhood of San Diego, California, United States. The university occupies 2,141 acres (866 ha) near the coast of the Pacific Ocean with the main campus resting on approximately 1,200 acres (490 ha). UCSD is organized into six undergraduate residential colleges and six graduate divisions, containing a total of 114 academic departments.

Established in 1960 near the pre-existing Scripps Institution of Oceanography, the university was first envisioned by Roger Revelle, then director of Scripps, to be a graduate school of science and engineering comparable in quality to Caltech. UC San Diego, the seventh oldest of the ten University of California campuses, offers over 200 undergraduate and graduate degree programs in a wide range of disciplines and enrolls about 23,000 undergraduate and about 5,500 graduate students from the United States and around the world. The university was admitted to the Association of American Universities in 1982.

UC San Diego is a designated sea and space grant institution and has a very high level of research activity with $879.3 million in research and development expenditures in 2009. The university operates four research institutes, including the California Institute for Telecommunications and Information Technology, San Diego Supercomputer Center, Scripps Institution of Oceanography, and UC San Diego Medical Center and is also affiliated with several regional research centers, such as the Salk Institute, the Burnham Institute for Medical Research, and the Scripps Research Institute. UC San Diego faculty, researchers, and alumni have won twenty Nobel Prizes, eight National Medals of Science, eight MacArthur Fellowships, and two Fields Medals. Additionally, of the current faculty, 29 have been elected to the National Academy of Engineering, 88 to the National Academy of Sciences, and 106 to the American Academy of Arts and Sciences.

UC San Diego student-athletes compete in 23 intercollegiate sports as the Tritons in Division II of the NCAA. As a member of the California Collegiate Athletic Association, the Tritons have won 24 championships in sports including soccer, volleyball, golf, tennis, water polo, and softball. The official colors of the university and its athletic teams are navy blue and California gold.