Euthydemus was a Greek physician who lived during the late Hellenistic or early Roman Imperial period. The date is uncertain, but modern scholars generally place his activity in the 1st century BCE or the 1st century CE. He was a member of the Empiricist school of medicine, which emphasized practical experience and observation over theoretical reasoning.

He is known to have written at least one medical treatise, but the work has not survived. It is lost and known today only through fragments and references in the writings of later physicians. The most important of these later sources is the renowned doctor Galen, who lived in the 2nd century CE. Based on Galen's citations, Euthydemus's treatise likely dealt with pharmacological treatments and therapies.

Euthydemus's historical importance stems from his role in ancient medical debates. According to modern scholars, he serves as an example of the Empiricist perspective, which was often contrasted with the Dogmatic or Rationalist school of thought. Galen cited Euthydemus's work when discussing these methodological conflicts about how medical knowledge should be obtained and applied. Therefore, although his own writings are lost, Euthydemus's ideas were preserved through Galen and contribute to our understanding of the diversity of medical practice in the ancient world.