Cleidemus (Greek: Kleidemos) was a Greek author, perhaps of the fifth or fourth century BCE but definitely later than the battle of Plataea in 479 BCE, who produced a lost book called Atthis (named for the mother of Erichthonius), dealing with the traditional origins of Athenian law and institutions. Meursius suggested that "Cleidemus" is actually identical with the "Cleitodemus" stated by Pausanius to be the most ancient writer on Athenian history. Athenaeus and Plutarch make references to his works, all of which are lost.[1]