Bunkoku (分国)

"Bunkoku" is a unit used to delineate province-sized areas during the medieval period in Japan. The term applied to Heian-period chigyo-koku (province-wide fiefs).

Starting in the mid-Heian period, "Bunkoku" also appears in the term "ingu gobunkoku," which refers to the province-sized territories controlled by the Retired Emperors, the Cloistered Emperors, and the Imperial Family, as well as in the term "kanto gobunkoku," referring to the bloc of provinces MINAMOTO no Yoritomo controlled in the Kanto (eastern Japan); starting in the period of Northern and Southern Courts (Japan), "bunkoku" was additionally used to describe the provinces controlled as feudal domains by the shugo daimyo (shugo, which were Japanese provincial military governors, that became daimyo, which were Japanese feudal lords).

Sengoku daimyo (Japanese territorial lord in the Sengoku period) during the Sengoku period (period of warring states) would come to rule their provinces by establishing an internal law called the Bungokuho, which had effect only within their own individual domains.