  We study how monopole catalysis of baryon decay is realized in holographic
QCD. Physics of monopole catalysis becomes much simpler in holographic
description as it occurs due to the violation of the Bianchi identity for the
5D gauge symmetry when magnetic monopole is present. In holographic QCD we find
a unified picture of the baryon number violation under magnetic monopole or
electroweak sphaleron, giving a new mechanism of baryon number violation. We
also embed our set-up in the string theory model by Sakai and Sugimoto.
