In Greek mythology, Tethys was a Titan daughter of Uranus and Gaia, a sister and wife of the Titan Oceanus, and the mother of the river gods and the Oceanids. Although Tethys had no active role in Greek mythology and no established cults, she was depicted in mosaics decorating baths, pools, and triclinia in the Greek East, particularly in Antioch and its suburbs, either alone or with Oceanus.

Greek mythology is the body of myths originally told by the ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories concern the ancient Greek religion's view of the origin and nature of the world; the lives and activities of deities, heroes, and mythological creatures; and the origins and significance of the ancient Greeks' cult and ritual practices. Modern scholars study the myths to shed light on the religious and political institutions of ancient Greece, and to better understand the nature of myth-making itself.