Hermodorus of Ephesus was a philosopher active in the 5th century BCE. He is known primarily as a disciple and close associate of the earlier thinker Heraclitus. Ancient sources report that Hermodorus was exiled from his home city of Ephesus. Following this exile, he traveled to Italy. According to a later tradition recorded by the Roman writer Cicero, Hermodorus was in Rome and assisted the officials drafting the city’s earliest law code, the Twelve Tables, by providing examples of Greek laws. This story places his activity in the mid-5th century BCE.

Hermodorus did not leave behind any surviving writings of his own. Instead, his significance lies in his role as a transmitter of Heraclitus’s ideas. Later sources, including a Byzantine encyclopedia, state that Hermodorus wrote a book about Heraclitus or was involved in publishing his master’s work. His primary contribution was therefore preserving and explaining the complex philosophy of Heraclitus for later generations.

Modern scholars view Hermodorus as an important bridge between different cultures and eras. As a direct disciple, he was a key link in passing on Presocratic thought. The story of his involvement with early Roman law, while its historical accuracy is debated, reflects an ancient belief in the influence of Greek philosophy on the development of Roman institutions. Through these traditions, Hermodorus represents a connection between the philosophical circles of Ionia and the early Roman Republic.