These are things named after Felix Klein (1849 – 1925), a German mathematician.(This list is incomplete; you can help by adding missing items with reliable sources.) * Klein bottle * Klein configuration * Klein cubic threefold * Klein four-group * Klein geometry * Klein graphs * Klein model * Klein polyhedron * Klein surface * Klein quadric * Klein quartic * Kleinian group * Kleinian integer * Kleinian model * Kleinian ring * Kleinian singularity * Beltrami–Klein model * Cayley–Klein metric * Schottky–Klein prime form * The Felix Klein Protocols * Felix Klein medal, named after the first president of the ICMI (1908–1920), honours a lifetime achievement in mathematics education research. * The Klein project of the IMU and ICMI aims to produce a book for upper secondary