Geb was the Egyptian god of the earth and a mythological member of the Ennead of Heliopolis. He could also be considered a father of snakes. It was believed in ancient Egypt that Geb's laughter created earthquakes and that he allowed crops to grow.

The oldest representation in a fragmentary relief of the god was as an anthropomorphic bearded being accompanied by his name, and dating from king Djoser's reign, 3rd Dynasty, and was found in Heliopolis. However, the god never received a temple of his own. In later times he could also be depicted as a ram, a bull or a crocodile (the latter in a vignette of the Book of the Dead of the lady Heryweben in the Egyptian Museum, Cairo).

Geb was frequently feared as father of snakes (one of the names for snake was s3-t3 – "son of the earth"). In a Coffin Texts spell Geb was described as father of the mythological snake Nehebkau of primeval times. In more mythology, Geb also often occurs as a primeval divine king of Egypt from whom his son Osiris and his grandson Horus inherited the land after many contendings with the disruptive god Set, brother and killer of Osiris. Geb could also be regarded as personified fertile earth and barren desert, the latter containing the dead or setting them free from their tombs, metaphorically described as "Geb opening his jaws", or imprisoning those there not worthy to go to the fertile North-Eastern heavenly Field of Reeds. In the latter case, one of his otherworldly attributes was an ominous jackal-headed stave (called wsr.t Mighty One') rising from the ground onto which enemies could be bound.

In the Heliopolitan Ennead (a group of nine gods created in the beginning by the one god Atum or Ra), Geb is the husband of Nut, the sky or visible daytime and nightly firmament, the son of the earlier primordial elements Tefnut (moisture) and Shu ('emptiness'), and the father to the four lesser gods of the system – Osiris, Seth, Isis and Nephthys. In this context, Geb was believed to have originally been engaged with Nut and had to be separated from her by Shu, god of the air. Consequently, in mythological depictions, Geb was shown as a man reclining, sometimes with his phallus still pointed towards Nut. Geb and Nut together formed the permanent boundary between the primeval waters and the newly created world. 

As time progressed, the deity became more associated with the habitable land of Egypt and also as one of its early rulers. As a chthonic deity he (like Min) became naturally associated with the underworld, fresh waters and with vegetation – barley being said to grow upon his ribs – and was depicted with plants and other green patches on his body.

His association with vegetation, healing and sometimes with the underworld and royalty brought Geb the occasional interpretation that he was the husband of Renenutet, a minor goddess of the harvest and also mythological caretaker (the meaning of her name is "nursing snake") of the young king in the shape of a cobra, who herself could also be regarded as the mother of Nehebkau, a primeval snake god associated with the underworld. He is also equated by classical authors as the Greek Titan Cronus.

Ptah and Ra, creator deities, usually begin the list of divine ancestors. There is speculation between Shu and Geb and who was the first god-king of Egypt. The story of how Shu, Geb, and Nut were separated in order to create the cosmos is now being interpreted in more human terms; exposing the hostility and sexual jealousy. Between the father-son jealousy and Shu rebelling against the divine order, Geb challenges Shu's leadership. Geb takes Shu's wife, Tefnut, as his chief queen, separating Shu from his sister-wife. Just as Shu had previously done to him. In the book of the Heavenly Cow, it is implied that Geb is the heir of the departing sun god. After Geb passed on the throne to Osiris, his son, he then took on a role of a judge in the Divine Tribunal of the gods.