Nuska or Nusku, possibly also known as Našuḫ, was a Mesopotamian god best attested as the sukkal (divine vizier) of Enlil. He was also associated with fire and light, and could be invoked as a protective deity against various demons, such as Lamashtu or gallu. His symbols included a staff, a lamp and a rooster. Various traditions existed regarding his genealogy, with some of them restricted to texts from specific cities. His wife was the goddess Sadarnunna, whose character is poorly known. He could be associated with the fire god Gibil, as well as with various courtiers of Enlil, such as Shuzianna and Ninimma.

The main cult center of Nuska was Nippur, where he is already attested in the Early Dynastic period. He was worshiped both in temples of his own and in the Ekur complex. He is attested in various documents from the Kassite period, including oath formulas and inscriptions, as well as in theophoric names. In later periods, he was introduced to the local pantheons of other cities, including Babylon, Ur and Uruk in the south and Assur and Harran in the north. The last of these cities might have served as his main cult center in the late first millennium BCE. Some attestations of the worship of Nuska are available from outside Mesopotamia, including inscriptions from Chogha Zanbil in Elam and Aramaic documents from Elephantine in Egypt.

In known myths, Nuska is typically portrayed as a servant of Enlil. He appears in this role in two different narratives about his marriage, Enlil and Sud and Enlil and Ninlil, in Atrahasis, in the Anzû narrative, and in other compositions. Hymns dedicated to him are known as well.

The etymology of Nuska's name is uncertain. Wilfred G. Lambert proposed that it was a shortened form of Sumerian en-usuk-ak, "lord of the scepter," though he noted the form usuk is speculative, and would require an interchange of a dental and sibilant in the uncommonly attested word udug, known from lexical lists. This proposal is implausible according to Jeremiah Peterson.

The standard cuneiform writing of the name was 𒀭𒉺𒌆 (^dPA+TÚG), though phonetic syllabic spellings are known too. Sometimes the two attested forms, Nuska and Nusku, are treated as, respectively, the Sumerian and Akkadian readings in modern literature. According to Michael P. Streck, the reading Nuska was older, though he asserts the form Nusku, written syllabically, appears already in Old Babylonian theophoric names, such as Ibi-Nusku and Idin-Nusku. However, Lambert pointed out that this assumption is mistaken, and Streck most likely misread unrelated names invoking Numushda. Gianni Marchesi in a more recent publication states that the reading Nusku is only attested after the Old Babylonian period. The logographic writing of Nuska's name could also be read as Enšadu, commonly etymologized as "the good hearted lord," but it remains uncertain if this was simply his alternate name, or an originally independent deity, possibly viewed as a divine shepherd.

Umunmuduru was the emesal form of Nuska's name. However, according to Mark E. Cohen this theonym initially referred to the deity Ninĝidru, who only came to be identified with Nuska at a later point in time.

In Aramaic, Nuska's name was spelled as nsk in texts from Babylonia and as nšk or nwšk in these originating elsewhere, in Assyria, Nerab and Elephantine. It is also possible that the theonym Našuḫ, attested in syllabic cuneiform texts from the Neo-Assyrian and Neo-Babylonian periods in theophoric names from Harran and its surroundings, represents a second West Semitic derivative of Nuska's name.

Nuska was considered the divine sukkal ("vizier") or sukkalmaḫ ("great vizier") of Enlil. While the holders of the historical office of sukkalmaḫ were the overseers of the regular sukkals, there is no indication that their divine counterparts also functioned this way, and Enlil had no other servants designated with either term. Nuska fulfilled all the functions usually assigned to this type of deities, namely acting as a doorkeeper and advisor of his master, overseeing his court, and mediating between him and human supplicants. He was also believed to be the keeper of Enlil's secrets and was said to gladden his heart. In Assyria, he was incorporated into the court of Ashur in the same role. A staff was considered the badge of the office of a vizier, and is therefore attested as Nuska's attribute. He could be called en-ĝidru, the "lord of the scepter." While no text directly mentions Enlil bestowing a staff upon him, it is presumed that it was believed that like other analogous deities he received it from his superior. A text from the reign of Ishme-Dagan states that he owed his position to Enlil and Ninlil.