In Japanese folklore, tsukumogami (付喪神 or つくも神, lit. "tool kami") are tools that have acquired a kami or spirit. According to an annotated version of The Tales of Ise titled Ise Monogatari Shō, there is a theory originally from the Onmyōki (陰陽記) that foxes and tanuki, among other beings, that have lived for at least a hundred years and changed forms are considered tsukumogami. In modern times, the term can also be written 九十九神 (literally ninety-nine kami), to emphasize the agedness.
According to Komatsu Kazuhiko, the idea of a tsukumogami or a yōkai of tools spread mostly in the Japanese Middle Ages and declined in more recent generations. Komatsu infers that despite the depictions in Bakumatsu period ukiyo-e art leading to a resurfacing of the idea, these were all produced in an era cut off from any actual belief in the idea of tsukumogami.
Because the term has been applied to several different concepts in Japanese folklore, there remains some confusion as to what the term actually means. Today, the term is generally understood to be applied to virtually any object "that has reached its 100th birthday and thus become alive and self-aware", though this definition is not without controversy.