Nergal (Sumerian: dKIŠ.UNU or dGÌR.UNU.GAL; ; Aramaic: ܢܸܪܓܲܠ; Nirgal) was a Mesopotamian god worshiped through all periods of Mesopotamian history, from Early Dynastic to Neo-Babylonian times, with a few attestations indicating that his cult survived into the period of Achaemenid domination. He was primarily associated with war, death, and disease, and has been described as the "god of inflicted death". He reigned over Kur, the Mesopotamian underworld, depending on the myth either on behalf of his parents Enlil and Ninlil, or in later periods as a result of his marriage with the goddess Ereshkigal. Originally either Mammitum, a goddess possibly connected to frost, or Laṣ, sometimes assumed to be a minor medicine goddess, were regarded as his wife, though other traditions existed, too.
His primary cult center was Kutha, located in the north of historical Babylonia. His main temple bore the ceremonial name E-Meslam and he was also known by the name Meslamtaea, "he who comes out of Meslam". Initially he was only worshiped in the north, with a notable exception being Girsu during the reign of Gudea of Lagash, but starting with the Ur III period he became a major deity in the south too. He remained prominent in both Babylonia and Assyria in later periods, and in the Neo-Babylonian state pantheon he was regarded as the third most important god, after Marduk and Nabu.
Nergal was associated with a large number of local or foreign deities. The Akkadian god Erra was syncretised with him at an early date, and especially in literary texts they functioned as synonyms of each other. Other major deities frequently compared to or syncretised with him include the western god Resheph, best attested in Ebla and Ugarit, who was also a god of war, plague and death, and Elamite Simut, who was likely a warrior god and shared Nergal's association with the planet Mars. It has also been proposed that his name was used to represent a Hurrian god, possibly Kumarbi or Aštabi, in early inscriptions from Urkesh, but there is also evidence that he was worshiped by the Hurrians under his own name as one of the Mesopotamian deities they incorporated into their own pantheon.