Renenutet was worshipped before the stone pyramids rose, her name appearing in the earliest religious texts of Egypt as the cobra who protected the storehouse and the nurse who sustained the king. Her name comes from the verb rnn, meaning "to fondle, to nurse, or to rear," and the Egyptians saw her as the divine mother who took the pharaoh into her coils from the moment of his birth and never let him go. In the Pyramid Texts, the earliest religious writings ever carved, she is called "Renenutet, Nurse of the King," and in Utterance 635 the deceased king is wrapped in the Renenutet-garment, a divine robe so powerful that the gods themselves respect it, ensuring that the pharaoh will be feared in the afterlife as he was feared on earth. She was the Lady of the Robes, the guardian of the king's clothing in the land of the dead, and every stitch of royal linen carried her blessing.

But Renenutet was far more than a royal nurse. She was the goddess of the harvest itself, the divine force that determined whether the grain would ripen, whether the grapes would sweeten, and whether the storehouses would be full or empty when the Nile receded. The Egyptians called her "Lady of the Granary, Mistress of Provisions" and "She Who Makes the Fields Flourish," and they placed her image in every place where food was stored or prepared. In kitchens she watched over the ovens, in cellars she guarded the wine jars, in granaries she protected the wheat from mice and insects, and in vineyards she received the first pressing of the grape. Amulets bearing her cobra form were pressed into the stoppers of wine amphorae, and stamps carved with her likeness sealed the containers that held Egypt's wealth. She was the cobra who killed the rodents that threatened the harvest, and her shedding skin was a symbol of renewal that mirrored the agricultural cycle itself: the old crop died, the new crop was born, and Renenutet shed her skin to begin again.

The most important temple of Renenutet stood at Medinet Madi in the Fayum, a region west of the Nile that the Egyptians transformed into a garden through irrigation and engineering. Here she was worshipped as the consort of Sobek, the crocodile god of the Nile's floods, and together they formed a divine pair that embodied the interdependence of water and grain. Sobek brought the inundation that fertilised the land, and Renenutet turned that water into wheat, barley, and grapes. The temple reliefs show Sobek presenting the was-sceptre, the symbol of power, to Renenutet, who stands as a cobra-headed woman clutching sheaves of wheat, and the inscriptions praise them as "Lord of the Waters and Lady of the Grain, Bound in Eternity." In this local theology they were also the parents of Horus the Child, the divine infant who represented the cyclical rebirth of the sun and the harvest, a triad that mirrored the greater Osiris-Isis-Horus family but was rooted in the soil and water of the Fayum.

Renenutet's power extended beyond agriculture into the most intimate mystery of Egyptian life: the secret name. The Egyptians believed that every person possessed a true name, a hidden set of syllables that contained their essence and their destiny, and that whoever knew this name held power over its bearer. Renenutet was called "She Who Is in the Name," the goddess who gave the child its true name at birth and who guarded that name throughout its life. In the Book of the Dead, the collection of spells that guided the soul through the shadowy underworld, she appears alongside Shai, the god of destiny, and the two of them together decree the fate of every mortal. Ramesses II, the great builder king of the Nineteenth Dynasty, called himself "Lord of Shai and Creator of Renenutet," a boast that claimed dominion over both fate and nourishment, the two forces that determine whether a man lives or dies.

As a snake goddess, Renenutet was gradually absorbed into the cults of other serpent deities. She was identified with Wadjet, the cobra goddess of Lower Egypt whose image reared upon the brow of every pharaoh as the uraeus, the protective serpent that spat fire at the king's enemies. She was also syncretised with Meretseger, the cobra goddess of the Theban necropolis who guarded the Valley of the Kings, and with Isis, the greatest goddess of all, who absorbed nearly every feminine divine power in the Late Period. Yet her independent cult never entirely vanished. The Festival of Renenutet was celebrated at the beginning of the harvest season, when the first crops were gathered and offered to her in gratitude, and another festival marked the ripening of the grain in early summer. In Thebes, the festival became particularly associated with Khonsu the Child, the youthful moon god, and the month of Pashons was named in his honour, but the offerings were still made to the Nourishing Serpent who had made the harvest possible.