Watatsumi (or Wadatsumi) is a sea god (Shinto) appearing in Japanese mythology. It is written 綿津見, 海神 (Wata no Kami), etc.
The word 'wata' is an ancient word for sea, 'tsu' means 'of,' and 'mi' means divine spirit, so 'Watatsumi' means 'divine spirit of the sea.'
It is also used as another name for the sea.
The Watatsumi god first to appear in Japanese mythology was Owatatsumi (Owatatsumi no Kami). It was born between the two gods, Izanagi and Izanami in the chapter of kamiumi (birth of the gods). From the shinmei (name of god), it is believed to be the leading god of the sea, but no god named Owatatsumi appears after this in kiki (the Kojiki (A Record of Ancient Matter) and Nihonshoki (Chronicles of Japan)), and is only described in the Yasugi-no-sato article of Izumo no kuni fudoki (the topography of Izumo Province) as Watazumi. In kiki, Izanagi ordered Susano to govern the sea.
When Izanagi returned from Yomi (world after death) and performed a purification ceremony, the three gods, Sokotsuwatatsumi, Nakatsuwatatsumi, and Uwatsuwatatsumi, were born, and these three god are collectively called Watatsumi no Kami. It is believed that it was originally one god, but was divided into the upper, middle, and lower three gods. Utsushihikanasaku, the child of Watatsumi no Kami, is described as the soshin (ancestor honored as god) of the Azumi clan. Sokotsutsunoo no Mikoto, Nakatsutsunoo no Mikoto, and Uwatsutsunoo no Mikoto, who are the Sumiyoshi Sanjin (Sumiyoshi three deities) or Sumiyoshi Okami (the great gods of Sumiyoshi), were born at the same time. Sumiyoshi no Kami was also a sea god, and the fact that the ujigami (a guardian god or spirit of a particular place in the Shinto religion) of Tsumori clan, the clan in charge of religious services at Sumiyoshi-taisha Shrine enshrining Sumiyoshi no Kami, was Owatatsumi-jinja Shrine, is indicative of the state of the relationship between Watatsumi no Kami and Sumiyoshi no Kami.
In the chapter of Yamasachihiko and Umisachihiko, Hoori (Yamasachihiko), who was in trouble after losing the fish hook of Hoderi (Umisachihiko), visited Watatsumi no Okami under the advice of Shiotsuchinooji, and married Toyotama-hime, the daughter of Watatsumi no Okami. Ugayafukiaezu, the child of the two gods, was brought up by Tamayori-hime, the sister of Toyotama-hime, and later married and gave birth to Emperor Jinmu and others. The origin of Watatsumi no Okami is not described, but it is considered to be the same god as Owatatsumi.