Ninmug or Ninmuga was a Mesopotamian goddess. She was associated with artisanship. This role was reflected in her epithet tibira kalamma, "metalworker of the land" or "sculptor of the land". She could also be regarded as a goddess of birth and assistant of Ninmah, most likely because the fashioning of statues of deities and the birth of children could be described with the same terms in Sumerian texts. Her main cult centers were Kisiga, whose location remains uncertain, and Adab.

From the Old Babylonian period onward, the god Ishum (and by extension his counterpart Hendursaga) could be regarded as her husband. While no children are attributed to him, Ninmug herself is addressed as the mother of the minor god Lumma in some sources. She was also associated with the underworld goddess Ereš'ugga based on similar writing of their names. While most researchers assume they were separate, it has also been proposed they were the same deity, and by extension that Ninmug could also be viewed as the wife of the sea god Lugala'abba.

The theonym Ninmug was written in cuneiform as ^dNIN.MUG. The reading was established based on the phonetic Emesal form, ga-ša-an-mu-ga, and on the phonetic gloss in the lexical list Diri, ni-im-mu-ug. ^dNIN.ZADIM might have been a variant spelling, though it has also bean argued that it should be read as Ninzadim, a distinct deity associated exclusively with seal cutters. Thorkild Jacobsen interpreted the name Ninmug as "lady vulva", but it is now assumed that element mug, which is also attested in personal names such as Mugsi (known from Adab) refers to an unidentified cultic utensil or building.

Ninmug was associated with artisanship and with birth. Most likely both functions were interlinked, and Antoine Cavigneaux and Manfred Krebernik [de] point out that the same terms could be used to refer to birth of children and fashioning of cult statues and statuettes. She was particularly closely connected with metalworkers. She was referred to with the Sumerian title tibira kalamma, "metalworker of the land". However, it has also been argued that the term tibira might have referred to a sculptor working with stone, ivory or wood, as opposed to a metalworker. If this assumption is correct, Ninmug's epithet would accordingly designate her as the "sculptor of the land" instead. She could be described as wielding a variety of tools related to her trade, such as a golden chisel, a silver burin and an obsidian knife. She was also associated with the investiture of kings, as attested in the myth Enki and the World Order.

It has been argued that in late periods Ninmug started to be viewed as a male deity. However, as noted by Cavigneaux and Krebernik, it is not certain if the male deity Nin-MUG, who could be equated with Ea and who is conventionally assumed to be a god of bowyers, can be necessarily interpreted as a male form of Ninmug, and it is possible that his name was instead read Ninzed or Ninzedim.

Ninmug is already attested in the Early Dynastic god list from Fara (Shuruppak), in which she precedes Ninšar. There is evidence that she was actively worshiped in this city. One of the Zame Hymns from Abu Salabikh from the same period associates her with Kisiga (Kissik). However, no other references to Kisiga have been identified in any sources from the third millennium BCE. The precise location of this city is unknown, but it is agreed that it was located in southern Babylonia, possibly in the Sealand. Texts from the first millennium BCE indicate it was close to Ur, Larsa, Uruk, Kullaba, Eridu and Nemed-Laguda. Identification with Tell al-Lahm is sometimes proposed. Later references to Kisiga are known from Old Babylonian texts and from between 1000 BCE and 600 BCE. It is known that it also functioned as a cult center of Inanna and Dumuzi or of Lugal-irra and Meslamta-ea.

Another major cult center of Ninmug was Adab, where at least before the Sargonic period she had her own temple. The eleventh month in the local calendar was named after her, as was a nearby canal. A sanga priest and officials involved in the cult of this goddess are also attested in documents from this city. In offering lists she appears after Ishkur or Nisaba. Offerings to Ninmug are also mentioned in records from Umma, while in Lagash she had a sanga priest.

In the Ur III and Old Babylonian periods, Ninmug could appear alongside her husband Ishum in cylinder seal inscriptions. It has been argued she was a popular deity at the time. References to her in personal letters are infrequent, though she nonetheless occurs comparably often as Ninsun or Ninkarrak. Theophoric names invoking Ninmug are known, one example attested in sources from between Early Dynastic and Ur III times being Ur-Ninmug.