Martin Eichler (29 March 1912 – 7 October 1992) was a German number theorist.
Eichler received his Ph.D. from the Martin Luther University of Halle-Wittenberg in 1936.
It has been claimed that Eichler once stated that there were five elementary operations of mathematics: addition, subtraction, multiplication, division, and modular forms. He is linked with Goro Shimura in the development of a method to construct elliptic curves from certain modular forms. The converse notion that every elliptic curve has a corresponding modular form would later be the key to the proof of Fermat's last theorem.