Tethys in Greek mythology, a goddess of the sea, daughter of Uranus (Heaven) and Gaia (Earth), and consort of Oceanus.

In astronomy, Tethys was the name given to a satellite of Saturn, the ninth closest to the planet and probably composed mainly of ice, discovered by Cassini in 1684. In geology, it is the name of an ocean formerly separating the supercontinents of Gondwana and Laurasia, the forerunner of the present-day Mediterranean.

Tethys (Saturn III) One of the major satellites of Saturn, with a radius of 529.9 km; mass 6.22 × 10²⁰kg; mean density 1000 kg/m³; visual albedo 0.9. It was discovered in 1684by G. D. Cassini.