Cleidemus of Athens (Κλείδημος ὁ Ἀθηναῖος) was a 5th-century BCE Athenian writer, recognized as the earliest known Atthidographer—a composer of local histories of Attica (Atthides) [1]. His work initiated the tradition of Athenian local historiography. Beyond this authorship, no secure biographical details survive; his dating is inferred from his foundational position in the genre preceding figures like Hellanicus [1][2].

His sole known work is the Atthis (Ἀτθίς), a history of Attica from mythical times to at least the late 5th century BCE. The text is lost, preserved only in fragments cited by later authors [1][2].

Cleidemus holds significance as the founder of Atthidography. His Atthis established a model for subsequent historians, creating a crucial genre focused on Athenian local traditions, cults, and institutions, which served as a counterpoint to pan-Hellenic history [1][2]. The fragments cited in later sources provide valuable evidence for early Athenian history and mythology.

Sources 1. Oxford Research Encyclopedia of Classics: Atthidography (Oxford University Press): https://oxfordre.com/classics/view/10.1093/acrefore/9780199381135.001.0001/acrefore-9780199381135-e-1022 2. Perseus Digital Library: Entry for "Cleidemus" in Smith's Dictionary of Greek and Roman Biography and Mythology (Tufts University): http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0104%3Aentry%3Dcleidemus-bio-1