The Civil war of Wa or Great Rebellion of Wa (倭国大乱 wakoku tairan?) was a period of disturbances and warfare in ancient Japan (Wa) during the late Yayoi period (2nd century AD). It is the oldest war in Japan that has been documented in writing. Peace was restored around 180, when the shaman queen Himiko (Pimiko) of Yamataikoku took control of the region.
The war falls into Japan's protohistoric period. While the earliest Japanese national chronicles Kojiki and Nihon Shoki begin their accounts from the Age of the Gods, they are largely mythological in nature, and the account in the Nihon Shoki is reliable as a history only after about the late 6th century. The Chinese Dynastic Histories are an important written source for Japanese history before the 6th century and contain the only written account of this 2nd century war. Japanese history is recounted in sections on the "barbarian" neighbours of China at the end of each dynastic history in the form of a footnote rather than a major chapter. Consequently, information on the conflict is very limited. The earliest mention is in the Wei Zhi (ca. 297), which is part of the Records of the Three Kingdoms. Subsequent histories mentioning the conflict such as the Book of the Later Han (ca. 445), the Book of Liang (635), the Book of Sui (636) and the History of Northern Dynasties (mid 7th century) draw much from earlier works.