Californium is named after the University of California, where it was first synthesized in 1950. The element was discovered by a team of scientists led by Glenn Seaborg, Albert Ghiorso, and Kenneth Street, Jr., who bombarded curium with alpha particles in the 60-inch cyclotron at the university. The resulting isotope, californium-242, had a half-life of only about 1.5 hours, but it was enough to allow the scientists to study its properties and confirm its identity as a new element.

Californium is the ninth transuranium element, and it is the heaviest element that can be produced in significant quantities in a nuclear reactor. It is a radioactive metal with a silvery appearance, and it is extremely toxic. Californium-252 is the most common isotope of californium, and it is used as a source of neutrons in a variety of applications, including neutron radiography, nuclear medicine, and oil well logging.