Christian Reiher (born April 19, 1984, in Starnberg) is a German mathematician. He is the second most successful participant in the history of the International Mathematical Olympiad, having won four gold medals in the years 2000 to 2003 and a bronze medal in 1999.

Just after finishing his Abitur, he proved Kemnitz’s conjecture, an important problem in the theory of zero-sums. He went on to earn his Diplom in mathematics from the Ludwig Maximilian University of Munich.

Reiher received his Ph.D. from the University of Rostock under supervision of Hans-Dietrich Gronau in February 2010 (Thesis: A proof of the theorem according to which every prime number possesses property B) and is now junior professor at the University of Hamburg.