Tenko (Japanese: 天狐) are a type of divine beast in Japanese folklore. After reaching 1,000 years of age and gaining its ninth tail, a kitsune (fox) turns a golden color, becoming a 'Tenko' (天狐 "heavenly fox"/"celestial fox"), the most powerful form of the kitsune, and then ascends to the heavens. They are able to see a thousand ri ahead (approx. 3927km or 2440 miles). They have nine tails unlike the lower-ranked existences, the yako, the kiko, and the kūko.
Tenko are of the highest rank of foxes in the Edo period, and in the essays "Zen'an Zuihitsu (善庵随筆)" and "Hokusō Sadan (北窓瑣談)," the foxes are ranked in the order of tenko, kūko, kiko, and then yako. Also, in the Nihon Shoki, in the 9th year of Emperor Jomei (637), the great shooting star was written as 天狗 (normally read "tengu") and was given the reading of "amatsu kitsune," and from this, the essay "Zen'an Zuihitsu" put forth the theory that tenko and tengu are the same.
Furthermore, at the first ridge of the Fushimi Inari-taisha, a male fox by the name of Osugi (小薄) is worshipped as Suehiro Daijin (末廣大神) (however, these foxes are always the divine messengers or household of Inari no Kami, not Inari no Kami himself).
In Ojika island in the Nagasaki Prefecture, the tenko is a type of spirit possession, and it is said that those who are possessed by it have a divination ability that is always correct, and is thus a divine spiritual power.