In Sumerian mythology and later for Assyrians and Babylonians, Anu (see also An) was a sky-god, the god of heaven, lord of constellations, king of gods, spirits and demons, and dwelt in the highest heavenly regions. It was believed that he had the power to judge those who had committed crimes, and that he had created the stars as soldiers to destroy the wicked. He was the father of the Anunnaku (also spelled Anunnaki). In art he was sometimes depicted as a jackal. His attribute was the royal tiara, most times decorated with two pairs of bull horns.

In Hurrian mythology, Anu was the progenitor of all gods. His son Kumarbi bit off his genitals and spat out three deities, one of whom, Teshub, later deposed Kumarbi.

In the Earth Chronicles series by Zecharia Sitchin, the wife of Anu was a fertility goddess and the mother of the gods; her cult was centered in Munster. However, Anu was one of the Anunnaki who came from the planet Nibiru (Marduk). Nibiru circles our sun but in a very elongated orbit which brings the planet to the vicinity of Earth only once in 3600 years. According to Sitchin's theories on Sumerian legend and lore, the Anunnaki arrived first on Earth probably 400,000 years ago, looking for minerals, especially gold, which they found and mined gold in Africa.

• Anu is also another name for the Celtic goddess Anann.
• Christine Anu is an Australian musician.
• For the ANU in Canberra, see Australian National University.