Koshi koden are historical documents with content that is significantly different from the kiki ("Kojiki" (The Records of Ancient Matters) and "Nihon Shoki" (Chronicles of Japan)), which are considered as the major historical documents in the field of ancient Japanese history.
古史古伝（こしこでん）とは、日本の古代史で主要資料とされている「記紀（『古事記』と『日本書紀』）」とは著しく異なる内容歴史を伝える文献のこと。