Geštinanna is an early goddess from southern Mesopotamia. She is the sister of Dumuzi and appears to be associated with writing and with the netherworld.
Geštinanna's exact functions remain unclear. It is possible that she was identified with the goddess Ama-geštin "Mother wine/vine," but this has to remain speculative (Edzard 1965: 67). She is referred to as "mother" (ama) or "old/wise woman" (um-ma), and, like other goddesses, functions as a dream interpreter (Black and Green 1998: 88), while her association with the netherworld is possibly a secondary development (Edzard 1957-71: 301).
In Sumerian mythology Geštinanna is considered to be the god Dumuzi's sister. She appears in the tale Dumuzi's Dream, a mourning song for the dead Dumuzi (Alster 1972; ETCSL 1.4.3. with further literature). The tale recounts an ominous dream, in which Dumuzi foresees his own death. Much of the tale involves Dumuzi trying to escape death in the form of demons, while his sister tries to protect him. Ultimately she is unsuccessful and Dumuzi dies. The tale Dumuzi and Geštinanna (ETCSL 1.4.2) similarly recounts Dumuzi trying to escape death and his sister trying to protect him but ultimately failing.
The tale of Inana's Descent to the Netherworld (ETCSL 1.4.1) also mentions Geštinanna, though not by name. It describes how the goddess Inana decides to conquer the realm of her sister Ereškigal, the netherworld. Ultimately, Inana succeeds in her endeavor but dies, which results in procreation on earth coming to an end. The god Enki, who often functions as the helper of humankind, decides to help Inana and rescues her from death. Yet not even a goddess can escape death without consequences: she has to find a substitute to go to the netherworld in her place. When she comes upon her hapless husband Dumuzi, who is celebrating instead of mourning while his wife is dead, she designates him to be her substitute. Inana then also designates Dumuzi's sister to be his substitute for six months out of the year.
In various praise poems of king Šulgi, Geštinanna is also associated with music and the scribal arts, and in the tale Dumuzi's Dream she is called a "scribe" and a "singer" by her brother Dumuzi (ETCSL 1.4.3. ll. 19-24).
[Note that the suggestion that it was Geštinanna who took away Gilgameš's toys in the tale of Gilgameš, Enkidu, and the Netherworld turned out to be incorrect after new manuscripts were discovered.]
As mentioned above, Geštinanna is the sister of Dumuzi, the shepherd, which makes her the sister-in-law of the goddess Inana and the sun-god Utu. She is the daughter of the goddess Durtur(Turdur/Duttur) (Edzard 1957-71: 300). In the pantheon of the city-state Lagaš, she is referred to as the wife of the god Ningišzida (ibid.). Beginning in the Old Babylonian period, she is also identified with the underworld goddess Belet-ṣeri ("Lady of the steppe") (ibid. 301). The goddess Belili is considered to be Geštinanna's sister as well (ibid.).
Geštinanna was mainly worshiped in the in southern Mesopotamia (Edzard 1957-71: 300). Most of the attestations date to the earlier periods of Mesopotamian history and her cult seems not to have survived the Old Babylonian period, although she continues to appear in god lists of later periods (ibid. 301). There is evidence that Geštinanna was worshiped in the cities of Nippur, Isin, and Uruk in the Old Babylonian period (Richter 2004: 162 et passim).
The earliest attestations of Geštinanna date to the Early Dynastic IIIb period. While her role changed during the Old Babylonian period, she continues to appear in Akkadian literary and scholarly texts until the Seleucid period, both as Geštinanna and as Belet-ṣeri (see below).
Geštinanna's iconography is unknown.
Nicole Brisch, 'Geštinanna/Belet-ṣeri (goddess)', Ancient Mesopotamian Gods and Goddesses, Oracc and the UK Higher Education Academy, 2016 [http://oracc.museum.upenn.edu/amgg/listofdeities/getinanna/]