Rikkokushi (六国史) is a general term for Japan's Six National Histories chronicling the mythology and history of Japan from the earliest times to 887. The six histories were written at the imperial court during the 8th and 9th centuries, under order of the Emperors. The basic sources were the court records kept by the Ministry of Central Imperial Affairs, and the biographies of meritorious officials composed in the Ministry of Ceremonial Affairs.
The collection consists of the following texts:
The historiography of Japan (日本史学史 Nihon shigakushi) is the study of methods and hypotheses formulated in the study and literature of the history of Japan.
The earliest work of Japanese history is attributed to Prince Shōtoku, who is said to have written the Tennōki and the Kokki in 620 CE. The earliest extant work is the Kojiki of 712. The Nihon Shoki followed by 720. These two works formed the base of a history of the nation based in great part on Japanese mythology, in particular that of the Shinto religion. The works were inspired by Chinese historiography and were compiled with the support of the Japanese state. Five more works between 797 and 901 completed what had begun with the Nihon Shoki; the six are known as the Rikkokushi ("six national histories").
The Shoku Nihongi (続日本紀) is an imperially-commissioned Japanese history text. Completed in 797, it is the second of the Six National Histories, coming directly after the Nihon Shoki and followed by Nihon Kōki. Fujiwara no Tsugutada and Sugano no Mamichi served as the primary editors. It is one of the most important primary historical sources for information about Japan's Nara period.
The work covers the 95-year period from the beginning of Emperor Monmu's reign in 697 until the 10th year of Emperor Kanmu's reign in 791, spanning nine imperial reigns. It was completed in 797 AD.
Nihon Kōki (日本後紀) is an officially commissioned Japanese history text. Completed in 840, it is the third volume in the Six National Histories. It covers the years 792–833.