Nanshe (Sumerian: 𒀭𒀏 ^dNANŠE (AB×ḪA)) was a Mesopotamian goddess in various contexts associated with the sea, marshlands, the animals inhabiting these biomes, namely bird and fish, as well as divination, dream interpretation, justice, social welfare, and certain administrative tasks. She was regarded as a daughter of Enki and sister of Ningirsu, while her husband was Nindara, who is otherwise little known. Other deities who belonged to her circle included her daughter Nin-MAR.KI, as well as Hendursaga, Dumuzi-abzu and Shul-utula. In Ur she was incorporated into the circle of Ningal, while in incantations she appears alongside Ningirima or Nammu.

The oldest attestations of the worship of Nanshe come from the Uruk period. Her cult center was Tell Zurghul, known in antiquity as Nina. Another place associated with her, Sirara, was likely a sacred district in this city. She was also worshiped elsewhere in the state of Lagash. Sanctuaries dedicated to her existed in its eponymous capital, as well as in Girsu, Gu'abba and other settlements. She is also attested in a number of other cities in other parts of Mesopotamia, including Adab, Nippur, Umma, Ur and Uruk, but her importance in their local pantheons was comparatively smaller. Her cult declined after the Ur III period. She was later adopted as a dynastic tutelary deity by the kings of the Sealand, and also came to be worshiped in the Esagil temple complex in Babylon. She was still venerated in the sixth century BCE.

Multiple literary texts focused on Nanshe are known. Nanshe and the Birds focuses on her relation with her symbolic animal, the u₅ bird. Its species is a matter of dispute, with proposed identifications including goose, swan, cormorant, gull and pelican. In the myth Enki and Ninhursag, she appears as one of the deities created by Ninhursag to cure Enki's illness. Other compositions deal with her relation to the sea, fish or dream interpretation.

The meaning of Nanshe's name is unknown, and it is agreed it has no plausible Sumerian etymology. It was written in cuneiform with the signs ^dAB×ḪA, with the dingir sign being a determinative designating names of the deities, while AB✕ḪA is a combination of the words "shrine" and "fish", with the latter written inside the former. A common phonetic variant, ^dna-zi, first appears in texts from Ebla, for example in the theophoric names of two Mariote singers, ur-na-zi and ur-na-zi-a, and by the Old Babylonian period came to be used equally commonly in lexical lists. In texts from the Sealand, it is the typical spelling. It is also present in An = Anum and in the myth Enki and Ninhursag. It has been proposed that it reflects a speculative variant form of the name, Nassi. It has also been interpreted as a possible emesal spelling. In the Nippur god list, the traditional spelling and ^dna-zi are juxtaposed as two orthographies of a single theonym. Further syllabic spellings are also known, for example ^dna-áš, na-an-še and na-aš-še. The last of them occurs in the Old Babylonian lexical list "Diri Nippur."

It is possible that ^dšar-ra-at-ni-na, "queen of Nina", was an alternate name of Nanshe. However, this name is only attested in a list of deities from the Sealand, and an alternative proposal is that it refers to Ishtar of Nineveh, though this proposal is not universally accepted either.

Andrew R. George notes that in the Canonical Temple List Sirara, a toponym associated with Nanshe, might have been reinterpreted as an alternate name of her.

Nanshe's functions have been described as "heterogeneous", and a variety of roles and presumed iconographic attributes are attested for her in primary sources.

Nanshe was associated with water. Wolfgang Heimpel argues she was believed to reside in the open sea, and points out individual texts allude to her playing with the waves and sea foam, or being born on the waterfront. However, the term ab, "sea", was also used to refer to marshlands in Sumerian and Nanshe has been described as the goddess of this biome. She was associated with the animals inhabiting it, namely fish and birds. The text Nanshe and the Birds calls her "the one who loves fish and fowl". These two groups of animals were commonly associated with each other in Sumerian literary texts. The inscription on one of the Gudea cylinders states that Nanshe's emblem was an u₅-ku, agreed to be a type of bird, though there is no single agreed upon translation, and proposals include "white swan", "sacred seagull", "holy goose" and "pure cormorant". In the past it was sometimes assumed this term referred to a part of a ship, perhaps prow or cabin, but this view is no longer accepted today. Various works of art depicting Nanshe in the company of birds presumed to be geese or swans are known. It is also possible images of a goddess sitting on a large bird known from seals from Lagash (and in one case Ur) can be identified as representations of her. In at least one text, a fish appears to be referred to as an emblem of Nanshe as well. In two hymns, she appears in company of various fish, presumed to be marine or anadromous: the "scepter fish," which she holds like the object it was named after; the "sandal fish;" the "fire fish," which provides light for her in the depths; the bellowing "bull fish;" and the "swallow fish." However, Bendt Alster noted there is no agreement among researchers if all of these names referred to real animals. The myth Enki and the World Order states that she was responsible for providing Enlil with fish as well.