Euthydemos and Euthydemus are two English transliterations of the same name in Greek (Εὐθύδημος). There are two characters of this name in Socratic literature.
In Book I of the Memorabilia, Xenophon relates Critias' passion for the young Euthydemos and how Socrates mocked him for it: Socrates had observed that Critias loved Euthydemos. Therefore Socrates tried to argue him out of it, saying that it was degrading for a free man and ill became someone "beautiful in body and mind" to importune, moreover for nothing good, his beloved to whom he should be a shining example. Critias, an Athenian sophist and politician, was the leader of the Thirty Tyrants who after the Peloponnesian War ruled for a short while over Athens c. 404 BCE.
Another Euthydemos is the eponymous character in one of Plato's dialogues, Euthydemus, written on logic and logical fallacies, or sophisms. The characters Euthydemos and his brother Dionysodorus are sophists questioned by Socrates in a confrontation of the Euthydemian eristic and the Socratic elenchus.
- Xenophon, Memorabilia, 1.15
- Plato, Euthydemus, 273a–304c