Kokushi were provincial officials in Classical Japan. They were nobles sent from the central government in Kyoto to oversee a province, a system that was established as part of the Taika Reform in 645, and enacted by the Ritsuryō system. There were four classes of kokushi, from the highest to the lowest: Kami (守), Suke (介), Jō (掾), and Sakan (目). In the Middle Ages, an acting governor called mokudai, the daikan of the kokushi, took over the local government of the province, while the kokushi returned to the capital to take on a supervising role.

The Taika Reforms were a set of doctrines established by Emperor Kōtoku in the year 645. They were written shortly after the death of Prince Shōtoku and the defeat of the Soga clan, uniting Japan. The reforms also artistically marked the end of the Asuka period and the beginning of the Hakuhō period. Crown Prince Naka no Ōe, Nakatomi no Kamatari, and Emperor Kōtoku jointly embarked on the details of the Reforms. Emperor Kōtoku then announced the era of "Taika" (大化), or "Great Reform".