Theo Geisel (born 24 August 1948 in Limburg an der Lahn, Hesse) is a German physicist. Geisel is a director at the Max Planck Institute for Dynamics and Self-Organization and professor of theoretical physics at the University of Göttingen. His research is primarily concerned with the behavior of complex systems ranging from theoretical investigations in quantum chaos to nonlinear phenomena occurring in the brain.
Geisel studied physics in Frankfurt and Regensburg. After graduating from the University of Regensburg in 1975, he worked as Post-Doc at the Max Planck Institute for Solid State Research in Stuttgart (1976–77) and at the Xerox Palo Alto Research Center (1978–79). In 1980, he returned to Regensburg as assistant professor. During 1983-87 he worked as a Heisenberg fellow, later he became professor for theoretical physics at the University of Würzburg (1988–89) and the University of Frankfurt (1989–96). During this time, he was awarded the prestigious Gottfried