A historical source is an original document or item that holds important information about the past. These sources are fundamental for understanding history and serve as clues for historical study.

Historical sources encompass a wide range of materials, such as coins, artifacts, monuments, literary works, documents, archaeological sites, oral transmissions, inscriptions, paintings, recorded sounds, images, and oral history. Even ancient relics and ruins can be considered historical sources. These sources are categorized into primary, secondary, and tertiary sources.