In quantum field theory, Seiberg duality, conjectured by Nathan Seiberg, is an S-duality relating two different supersymmetric QCDs. The two theories are not identical, but they agree at low energies. More precisely under a renormalization group flow they flow to the same IR fixed point, and so are in the same universality class.
It was first presented in Seiberg's 1994 article Electric-Magnetic Duality in Supersymmetric Non-Abelian Gauge Theories. It is an extension to nonabelian gauge theories with N=1 supersymmetry of Montonen-Olive duality in N=4 theories and electromagnetic duality in abelian theories.
Read more about Seiberg Duality: The Statement of Seiberg Duality, Relations Between The Original and Dual Theories, Evidence For Seiberg Duality, Generalizations