Otmar D. Wiestler (born 6 November 1956 in Freiburg im Breisgau) is a German physician, a professor at the University of Heidelberg and president of the Helmholtz Association.
Under the direction of Paul Kleihues and Benedict Volk, Wiestler worked as assistant at the University of Freiburg until 1994, when he finished his thesis with summa cum laude.
As a PostDoc he joined Gernot Walter for three years at the Institute of Pathology at the University of California San Diego.
From 1987 to 1992 he was staff physician at the Department of Neuropathology at the Institute of Pathology of the University Hospital in Zürich, Switzerland, again with Paul Kleihues.
In 2004, Wiestler succeeded Harald zur Hausen as Chairman and scientific member of the Foundation Board of the German Cancer Research Centre (DKFZ).