Nusku was the name of the light and fire-god in Babylonia and Assyria, who is hardly to be distinguished, from a certain time on, from a god Girra - formerly Gibil.
Nusku-Girru is the symbol of the heavenly as well as of the terrestrial fire. As the former he is the son of Anu, the god of heaven, but he is likewise associated with Enlil of Nippur as the god of the earth and regarded as his first-born son. A centre of his cult in Assyria was in Harran, where, because of the predominating character of the moon-cult, he is viewed as the son of the moongod Sin, though Nusku was with Enlil when Sin wasn't born yet, and Enlil hadn't married Ninlil - Sin's mother. Nusku-Girru is by the side of Ea, the god of water, the great purifier. It is he, therefore, who is called upon to cleanse the sick and suffering from disease, which, superinduced by the demons, was looked upon as a species of impurity affecting the body.
The fire-god is also viewed as the patron of the arts and the god of civilization in general, because of the natural association of all human progress with the discovery and use of fire. As among other nations, the fire-god was in the third instance looked upon as the protector of the family. He becomes the mediator between humanity and the gods, since it is through the fire on the altar that the offering is brought into the presence of the gods.
While temples and sanctuaries to Nusku-Girru are found in Babylonia and Assyria, he is worshipped more in symbolical form than the other gods. For the very reason that his presence is common and universal he is not localized to the same extent as his fellow-deities, and, while always enumerated in a list of the great gods, his place in the systematized pantheon is more or less vague. The conceptions connected with Nusku are of distinctly popular origin, as is shown by his prominence in incantations, which represent the popular element in the cult, and it is significant that in the astro-theological system of the Babylonian priests Nusku-Girru is not assigned to any particular place in the heavens.