Csillebérc KFKI Site is a scientific and institutional campus in Budapest, Hungary, with roots in the Central Research Institute for Physics (KFKI), established in 1950. Today, the site is home to two major research centres: the HUN-REN Centre for Energy Research and the HUN-REN Wigner Research Centre for Physics. It also hosts organizations including the Budapest Neutron Centre, an environmental service, professional associations, foundations, and scientific publications.

The campus has a long history of research in fields such as particle and nuclear physics, materials science, optics, energy, and space exploration. Its researchers and predecessor institutes contributed to projects ranging from reactor research and computing to space instruments and radiation measurement.

Since 1992, KFKI Üzemeltető Kft. has been responsible for maintaining the site. The website serves the campus community and visitors with practical information and resources, including contact details, a directory, IT services, library information, dining options, a salad bar, a medical clinic, and sports and recreation information. It also shares site news and historical material.