The name Cecrops means 'face with a tail' and it is said that this mythical Greek king, born from the earth itself, had his top half shaped like a man and the bottom half in serpent or fish-tail form. He was first king and founder of Athens itself, though preceded in the region by earth-born Actaeus , king of Attica. Cecrops was a culture-hero, teaching the Athenians marriage, reading and writing, and ceremonial burial.

During his reign Athena became the patron goddess of the city of Athens in a competition with Poseidon which Cecrops judged. They agreed that each would give the Athenians one gift and Cecrops would choose whichever gift they preferred. Poseidon struck the ground with his trident and a spring sprang up; the water was salty and was not thought very useful, whereas Athena struch the rock with her lance and an olive tree sprung up. Cecrops judged the olive tree to be the superior gift, for the olive tree brought wood, oil and food, and consequently accepted Athena as their patron. Poseidon, in a rare show of magnanimity, decided to grant his gift regardless, although its nature was initially misunderstood: it was meant to represent sea power, which Athens were to exercise gloriously in the future.

The Acropolis was also known as the Cecropia in his honor.

Cecrops I was the father of three daughters: Herse, Pandrosus and Aglaurus. To them was given a box or jar containing the infant Erichthonius of Athens to guard unseen. They looked, and terrified by the two serpents Athena had set within to guard the child, they fled in terror and lept from the Acropolis to their deaths. Some accounts say one of the sisters was turned to stone instead.

Cecrops' son Erysichthon predeceased him and he was succeeded by Cranaus.