Mimas (pronounced /ˈmaɪməs/, or as Greek Μίμᾱς, rarely Μίμανς) is a moon of Saturn which was discovered in 1789 by William Herschel. It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I. By diameter, Mimas is the 20th largest moon in the solar system. However, Mimas is the smallest known astronomical body that is thought to be rounded in shape due to self-gravitation.