Democritus of Ephesus was a Hellenistic historian from Ephesus in Ionia, active during the 3rd century BCE. He is distinguished from the philosopher Democritus of Abdera. No substantive biographical details survive beyond his authorship of a local history.

His sole known work is a local history of Ephesus, titled Persika or On Ephesus. The work is now lost, surviving only in fragments which indicate it treated the city’s foundation myths and early history. Democritus represents the Hellenistic tradition of local history, which articulated civic identity through origins and legends. His inclusion in ancient catalogs and citations by later grammarians, such as Athenaeus, confirm his place in the period’s scholarly landscape.