Kokushi (国司, also read Kuni no tsukasa) were officials in Classical Japan sent from the central government to oversee a province from around the 8th century, after the enactment of the Ritsuryō system. Kokushi held considerable power and responsibility according to the Ritsuryō, including tax collection, etc. The highest level for a Kokushi was Kami (守). So, for instance, the chief kokushi (governor) of Kai would have the title of Kai no Kami (甲斐守). In some cases, the Kami himself was living directly in the province he was charged with, delegating his powers to lower ranking officials. The highest official effectively in charge of the province was called Zuryō (受領).
Kokushi lost their power during the Kamakura shogunate and furthermore during the Muromachi Shogunate to the Shugo. In subsequent generations, especially in the Edo period, a kokushi title remained as an honorific title.