Atum was a sun god and, according to the priests of his cult, creator of the universe. His name is derived from a word that meant both 'to be complete' and to 'make an end of'. This concept is clearly seen in his position as a father of the gods. He was the original god of Heliopolis, preceding Ra, but even from the earliest times the two gods were closely identified with each other. They are linked in legend, and many similarities exist in the stories associated with them, to the point where their names may be considered to be interchangeable.

Sometimes Atum represented the sun in the evening while Ra was the sun in the morning In sacred art Atum is shown wearing the double crown of united Egypt and, as the creator, he carries an ankh, the symbol of life. Several animals were associated with Atum, including the lion, bull, lizard, ichneumon (a type of mongoose), and snake. In the snake form Atum represents the concept of the end of the universe, following which only he and Osiris survive. The Book of the Dead speaks of a time when the waters of Nun will rise up and engulf the earth, consuming both men and gods, and leaving only Osiris and Atum living on in the form of serpents.