Anu (Akkadian: 𒀭𒀀𒉡 ANU, from 𒀭 an "Sky", "Heaven") or Anum, originally An (Sumerian: 𒀭 An), was the divine personification of the sky, king of the gods, and ancestor of many of the deities in ancient Mesopotamian religion. He was regarded as a source of both divine and human kingship, and opens the enumerations of deities in many Mesopotamian texts. At the same time, his role was largely passive, and he was not commonly worshipped. It is sometimes proposed that the Eanna temple located in Uruk originally belonged to him, rather than Inanna. While he is well attested as one of its divine inhabitants, there is no evidence that the main deity of the temple ever changed; Inanna was already associated with it in the earliest sources. After it declined, a new theological system developed in the same city under Seleucid rule, resulting in Anu being redefined as an active deity. As a result he was actively worshipped by inhabitants of the city in the final centuries of the history of ancient Mesopotamia.
Multiple traditions regarding the identity of Anu's spouse existed, though three of them—Ki, Urash, and Antu—were at various points in time equated with each other, and all three represented earth, similar to how he represented heaven. In a fourth tradition, more sparsely attested, his wife was the goddess Nammu instead. In addition to listing his spouses and children, god lists also often enumerated his various ancestors, such as Anshar or Alala. A variant of one such family tree formed the basis of the Enūma Eliš.
