According to Heliopolitan myth the sun had first risen in the form of a sacred bird called the benu, popularized as the phoenix by the Greeks. In some accounts the benu was a form of the creator Atum, or associated with the benben stone that symbolized the primeval mound.

The benu was also associated with the sacred ished (persea) tree, which had solar significance from Apophis by the Great Cat of Heliopolis, sacred to Re. In the Pyramid Texts the benu appeared as a yellow wagtail, a manifestation of the Heliopolitan sun god Atum. Its name translated as "to rise in brillance." Later, however, in The Book of the Dead, it was represented in its common form as the grey heron. Either way, it was seen as a symbol of rebirth and a harbinger of good fortune. In the form of a heron, it was described as perching above the water of chaos, occasionally breaking the silence with a cry. The bird's call created a disturbance that set the creation act in motion, determining "what is and what is not to be." This myth reflected that of Amun honking like a goose on the waters of Nun, causing a similar cosmic catacylsm. When the heron settled on the primeval mound it laid an egg which hatched to produce the sun god. Herodotus recorded it as the phoenix, a bird like an eagle with red and gold plumage that supposedly lived in the Arabian peninsula. There was never more than one alive at any time. When it died, its successor carried the carcass to the sun god's temple at Heliopolis. In another Greek story that encapsulated the benu's mysterious qualities, the phoenix was supposed to set fire to itself and be reborn from the ashes.