Amenooshihomimi (Masakatsuakatsu kachihayahi amenooshihomimi) is a god (Shinto) that appeared in Japanese mythology. It is written in kanji as 正勝吾勝勝速日天忍穂耳命 or 正勝吾勝勝速日天之忍穂耳命 in Kojiki (The Records of Ancient Matters), 天忍穂耳命 in Nihonshoki (Chronicles of Japan), and 正哉吾勝々速日天押穂耳尊 in Sendai Kujihongi (Ancient Japanese History).
In Kojiki, it is written that he was the first boy (the second boy in an Arufumi [supplement volumes of explanatory notes in Nihonshoki] of Nihonshoki) of five princes who were born when Susanoo (a deity in Japanese mythology) was given a magadama (comma-shaped bead) by Amaterasu (the sun goddess) during their ukei (pledge). It is also written that he was a son of Amaterasu who had a monozane (medium to produce something). He had children, Amenohoakari and Ninigi, with Takamimusubi's daughter, Takuhatachijihime no Mikoto.
When Ashihara no Nakatsukuni (literally, "Central Land of Reed Plains," which refers to the human world) was pacified, he was ordered by Amaterasu to come down from the celestial world and govern it. However he turned back halfway saying the human world was too dangerous. When the land was transferred from Okuninushi (chief god of Izumo in southern Honshu Island, Japan, and the central character in the important cycle of myths set in that region) by the order of Takemikazuchi and others, he was told to go down there again. But he suggested that his son, Ninigi, who was born during that time would go there, therefore Ninigi went down (this occurrence is called tensonkorin).
The name 'Masakatsuakatsu' means 'I won properly, I did' and 'Kachihayahi' means 'Winning was as fast as the sun rise,' and they are thought to be an announcement of winning ukei. The word, 'Oshiho' means many ears of rice, and this indicates he is a deity of rice ears.
He is believed to be a deity of rice ears and agriculture, and enshrined in Toda-hachimangu Shrine and Katsuhi-jinja Shrine (Yasugi City, Shimane Prefecture), Tarobo-no-miya Shrine (or Aga-jinja Shrine, Higashiomi City, Shiga Prefecture), Hikosan-jingu Shrine (Soeda-machi, Tagawa-gun, Fukuoka Prefecture), Sasamuta-jinja Shrine (Oita City, Oita Prefecture), Kibata-jinja Shrine (Uji City, Kyoto Prefecture), and Amenooshihowake-jinja Shrine (Kagami-cho, Kami-gun, Kochi Prefecture).