He is the son Enlil sends when something has to be killed, and he is also the god of the plough. Those two jobs are not in tension in Mesopotamia — the same seasonal violence that clears a channel of silt clears a mountain of raiders — but the combination gives him an unusual literature, in which a monster-slaying epic ends with a lecture on mineralogy and an irrigation scheme.
In Lagash he is called Ningirsu, "lord of Girsu", and whether that began as a separate god absorbed into him or as a local name is the standard unresolved question. His mace is Sharur, "smasher of thousands", and it is a character: it flies off on its own to scout, comes back with intelligence, and argues with him.
Lugal-e, and the strangest ending in Sumerian poetry
Lugal-e runs to over seven hundred lines and is one of the longest Sumerian compositions. Its antagonist is the Asag, a demon engendered in the mountains, whose presence is a physical pathology — where he passes, fish boil in the rivers, and the text describes his effect as a fever and a chill at once. He has an army, and it is made of stones.
The fight goes badly at first; Ninurta is driven back and Sharur flies to Nippur for advice. He returns, raises a dust storm, and destroys the Asag. Then, instead of ending, the poem turns into a courtroom. Ninurta passes judgement on each type of stone according to how it behaved in the battle. The flint, which fought, is condemned to be split by tools forever. The diorite, which submitted, is honoured and appointed to receive royal inscriptions — which is exactly what diorite was used for in Sumer, as the statues of Gudea in the Louvre demonstrate. Lapis, alabaster, carnelian and a long list of others each get a destiny that matches their actual industrial use.
And then he builds. He piles the mountain rubble into a barrier, gathers the waters that had been scattered and directs them into the Tigris so that the fields are watered and the canals run — and he names the pile hursag, the foothills, dedicating it to his mother, which is where Ninhursag gets her title. A monster-slaying poem that concludes with a flood-control project, a geology lesson and an etymology is doing something no Greek epic ever attempts.
Trophies on the chariot
Its companion piece, Angim — "Ninurta's Return to Nippur" — is a triumph procession, and its interest is the cargo list. Hanging from his chariot are the six-headed wild ram, the seven-headed serpent, the bison, the palm-tree king, the magillum boat, gypsum, copper, and the Anzu bird. These are the spoils of adventures, several of which do not survive as narratives at all; the trophy rack is our only evidence that some of those stories existed. His arrival at the Ekur is so overwhelming that Enlil's minister has to ask him to calm down before entering.
The Anzu episode did survive, in an Akkadian epic of its own, and it is where he earns his standing among the gods.
Girsu, Gudea, and the longest text in Sumerian
At Lagash the same god commissioned an unusually complete building record. The Gudea Cylinders, two large clay cylinders from around 2100 BCE, describe a dream in which a huge man with a bird's wings and a lion's lower body instructs the ruler Gudea to build his temple; Gudea consults a dream-interpreting goddess, obtains a confirming omen, and then constructs the Eninnu — with the timber, stone and metal sourced from named foreign regions, the brickmaking rites, the workforce arrangements and the dedication festival all recorded. It is the longest surviving Sumerian literary text and simultaneously an architectural report.
The Assyrians took him up with enthusiasm. Ashurnasirpal II built him a temple with a ziggurat at Kalhu, the city excavators call Nimrud, and Assyrian kings modelled their own campaign rhetoric on his — the god who goes to the mountains and comes back with trophies being an obvious template for an empire whose economy ran on exactly that.
The farmer's god
A Sumerian text usually called the Farmer's Instructions is a practical agricultural manual in verse: when to flood the field, how many times to harrow, how to set the seeder-plough's furrows, how to deal with weeds, when to stop watering the barley, how to winnow. It closes by attributing the instruction to Ninurta as the farmer of Enlil. So the same god whose epic sorts stones by hardness is credited with the country's agronomy handbook — and Sumerian schools taught both.
What people want to know
Is Nimrod in Genesis the same figure?
It is one proposal among several and it should not be stated as fact. The biblical Nimrod is "a mighty hunter before the Lord" who founds cities in Shinar including Babel, Erech and Akkad, and scholars have connected the name variously to Ninurta, to Naram-Sin of Akkad, to the Assyrian kings' hunting ideology in general, and to the Egyptian Amenhotep III. The Ninurta case rests on the shared profile of a divine hunter-warrior associated with Mesopotamian city-founding, not on the name itself, which does not derive from Ninurta by any regular sound change. The modern site name Nimrud for Kalhu is a later Arabic tradition and cannot be used as evidence.
Which star is he?
Both the Arrow star — Sirius, the brightest in the sky, listed in the astronomical texts as KAK.SI.SÁ — and, in other first-millennium material, the planet Saturn. Multiple identifications for one god are normal in Babylonian astral theology rather than a contradiction: the correspondences were made by scholars over centuries for different purposes, and the god-star equations in the omen literature are not a single consistent system. Treat any confident one-line answer about which star a Mesopotamian god "is" with suspicion.
Why does his mace get to talk?
Because it is not simply a weapon. Sharur is named, personified and given an independent errand in the narrative, and the same treatment is given to other divine objects in this literature — the Tablet of Destinies confers authority on whoever holds it regardless of who they are, and Marduk's net and winds are enumerated as participants in his battle. Mesopotamian myth is comfortable with instruments that have standing. It is worth noticing that the culture producing these stories is the one that invented the sealed contract and the deed, where an object legitimately does things a person would otherwise have to do.