The Lorentz Institute, or Instituut-Lorentz in Dutch, was established in 1921 and is the oldest institute for theoretical physics in The Netherlands. Together with the experimental physics groups in the Kamerlingh Onnes Laboratory and the Huygens Laboratory, it makes up the Leiden Institute of Physics. The Instituut-Lorentz participates in two research schools, the Casimir Research School (jointly with Delft University of Technology) and the Dutch Research School of Theoretical Physics.