Emil Wiechert was well known during his lifetime as Professor of Geophysics at the Georg-August-Universität in Göttingen and Director of the Geophysical Institute there. He made many significant contributions to geophysics and seismology, and is highly respected by present-day geophysicists for his research and organizational contributions to the development of geophysics and seismology as major scientific disciplines. On the other hand, his contributions to fundamental physics—cathode rays, the discovery of the electron, the Liénard–Wiechert potentials, his electron theory—are unknown to many physicists today. This article presents Wiechert’s life, achievements in physics, and relationship to well-known physicists like Arnold Sommerfeld, Hendrik Lorentz, and Woldemar Voigt, to enable contemporary physicists to know better Wiechert’s important contributions to pure physics, and to appreciate more fully his role in the history of physics. © 2001 American Association of Physics Teachers.