A kannushi (神主?, "god master", originally pronounced kamunushi), also called shinshoku (神職?) (meaning god's employee), is the person responsible for the maintenance of a Shinto shrine (神社 jinja?) as well as for leading worship of a given kami. The characters for kannushi are sometimes also read jinshu with the same meaning.
Originally the kannushi were intermediaries between kami and could transmit their will to common humans. A kannushi was a man capable of miracles or a holy man who, because of his practice of purificatory rites, was capable to work as a medium for a kami, but later the term evolved to being synonymous with shinshoku, that is, a man who works at a shrine and holds religious ceremonies there.
In ancient times, because of the overlap of political and religious power within a clan, it was the head of the clan who led the clansmen during religious functions, or else it could be another official. Later, the role evolved into a separate and more specialized form. The term appears in both the Kojiki (680 AD) and Nihon Shoki (720 AD). In them respectively, Empress Jungū and Emperor Suijin become kannushi.
Within the same shrine, for example at Ise Jingū or Ōmiwa Shrine, there can be different types of kannushi at the same time called for example Ō-kannushi (大神主?), Sō-kannushi (総神主?), or Gon-kannushi (権神主?).