Cleidemus was a Greek

Greeks

The Greeks, also known as the Hellenes , are a nation and ethnic group native to Greece, Cyprus and neighboring regions. They also form a significant diaspora, with Greek communities established around the world....

 author, perhaps of the fifth or fourth century BCE but definitely later than the battle of Plataea

Plataea

Plataea or Plataeae was an ancient city, located in Greece in southeastern Boeotia, south of Thebes. It was the location of the Battle of Plataea in 479 BC, in which an alliance of Greek city-states defeated the Persians....

 in 479 BCE, who produced a lost book called Atthis (named for the mother of Erichthonius

Erichthonius

Erichthonius may refer to:*Erichthonius of Athens*Erichthonius of Dardania...

), dealing with the traditional origins of Athenian

Athens

Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

 law and institutions. Meursius

Johannes Meursius

Johannes Meursius , was a Dutch classical scholar and antiquary.-Biography:...

 suggested that "Cleidemus" is actually identical with the "Cleitodemus" stated by Pausanius to be the most ancient writer on Athenian history. Athenaeus

Athenaeus

Athenaeus , of Naucratis in Egypt, Greek rhetorician and grammarian, flourished about the end of the 2nd and beginning of the 3rd century AD...

 and Plutarch

Plutarch

Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...

make references to his works, all of which are lost.