The University of California, San Francisco (UCSF) is a public land-grant research university in San Francisco, California. It is part of the University of California system and is dedicated entirely to health science and life science. It conducts research and teaching in medical and biological sciences.

UCSF was founded as Toland Medical College in 1864. in 1873, it became affiliated with the University of California as its Medical Department. In the same year, it incorporated the California College of Pharmacy and in 1881 it established a dentistry school. Its facilities were located in both Berkeley and San Francisco. In 1964, the school gained full administrative independence as a campus of the UC system, headed by its own chancellor, and in 1970 it gained its current name. Historically based at Parnassus Heights with satellite facilities throughout the city, UCSF developed a second major campus in the newly redeveloped Mission Bay district in the early 2000s.

U.S. News & World Report's 2022–23 rankings recognize the UCSF school of medicine as the third best medical school for research in the nation (tied with medical schools of Columbia University and Johns Hopkins University) and as the second best medical school for primary care. It is the only medical school to rank in the top three in both categories. In 2022, UCSF attracted the 2nd highest research funding from the National Institutes of Health. The UCSF Medical Center is ranked 12th nationally and third in the state. In 2021, the university spent $1.71 billion in research and development, the second most among institutions of higher education in the U.S.

With 25,398 employees, UCSF is the second-largest public agency employer in the San Francisco Bay Area. UCSF faculty have treated patients and trained residents since 1873 at the San Francisco General Hospital and for over 50 years at the San Francisco VA Medical Center.