Günter Harder (born 14 March 1938 in Ratzeburg) is a German mathematician, specializing in arithmetic geometry and number theory.

With the exception of a six-year stay at the former Universität-Gesamthochschule Wuppertal, Harder remained at the University of Bonn until his retirement in 2003.

[citation needed] Harder's doctoral students include Kai Behrend, Jörg Bewersdorff, Joachim Schwermer, and Maria Heep-Altiner.

[1] His research deals with arithmetic geometry, automorphic forms, Shimura varieties, motives, and algebraic number theory.

Harder was an invited speaker at the International Congress of Mathematicians in 1970 and gave a talk titled Semisimple group schemes over curves and automorphic functions[3] and in 1990 with a talk titled Eisenstein cohomology of arithmetic groups and its applications to number theory.