Uranus (pronounced /ˈjʊərənəs, jʊˈreɪnəs/) is the Latinized form of Ouranos (Οὐρανός), the Greek word for sky. In Greek mythology Ouranos or Father Sky, is personified as the son and husband of Gaia, Mother Earth (Hesiod, Theogony). Uranus and Gaia were ancestors of most of the Greek gods, but no cult addressed directly to Uranus survived into Classical times, and Uranus does not appear among the usual themes of Greek painted pottery. Elemental Earth, Sky and Styx might be joined, however, in a solemn invocation in Homeric epic.

Most Greeks considered Uranus to be primordial (protogenos), and gave him no parentage. Under the influence of the philosophers, Cicero, in De Natura Deorum ("The Nature of the Gods"), claims that he was the offspring of the ancient gods Aether and Hemera, Air and Day. According to the Orphic Hymns, Ouranos was the son of the personification of night, Nyx. His equivalent in Roman mythology was Caelus, likewise from caelum the Latin word for "sky".