Simöeis was a son of Oceanus and Tethys, and the father of Astyoche and Hieromneme. He was a god of the river Simöeis which flowed from Mount Ida (and is today called the Dombrek).

His name, disconcertingly, means either 'flat', or 'steep', or 'hollow', 'concave' (simos). In view of the location of the river, and its source on Mount Ida, the last sense seems the most appropriate, referring to the channel worn by the river in the mountain-side.