The Menashi-Kunashir rebellion or war (クナシリ・メナシの戦い Kunashiri Menashi no tatakai) or Menashi-Kunashir battle was a battle in 1789 between Ainu and Japanese on the Shiretoko Peninsula in northeastern Hokkaidō. It began in May 1789 when Ainu attacked Japanese on Kunashir Island and parts of the Menashi District as well as at sea. More than 70 Japanese were killed. The Japanese executed 37 Ainu identified as conspirators and arrested many others. Reasons for the revolt are not entirely clear, but they are believed to include a suspicion of poisoned sake being given to Ainu in a loyalty ceremony, and other objectionable behavior by Japanese traders.
The battle is the subject of Majin no Umi, a children's novel by Maekawa Yasuo that received the Japanese Association of Writers for Children Prize in 1970.
A similar large-scale Ainu revolt against Japanese influence in Yezo was Shakushain's Revolt from c. 1669–1672.