The Casimir Research School is a graduate school for interdisciplinary physics of the Leiden Institute of Physics (LION) at Leiden University and the Kavli Institute of Nanoscience at Delft University of Technology. It started formally on September 15, 2004 as the logical outcome of developments in the years before. The core of the research-programme is in the area of physics, with a focus on research-themes which interact strongly with developments and skills in other disciplines (interdisciplinary physics). Casimir offers courses and workshops and coordinates the PhD training of students working with research groups in the Kavli Institute of Nanoscience at Delft and the Leiden Institute of Physics. About 120 Ph.D. students, 50 post-docs and 50 senior researchers participate in the school's programme.

The research school is named after H.B.G. Casimir (1909-2000), professor in Theoretical Physics at the University of Leiden, whose involvement in fundamental as well as applied physics left many traces in the Dutch scientific landscape. Casimir worked with scientist like Niels Bohr and Wolfgang Pauli, and headed the worldwide research efforts of the Philips company. He is remembered mostly for his discovery of the so-called Casimir effect and for his ideas on science and research-management. Casimir had strong ties with both Delft and Leiden Universities.