Critias (krĬsh´ēəs, krĬtēəs), c.460–403 BC, Athenian political leader and writer. A relative of Plato, he was an aristocrat and had early training in philosophy with Socrates and wrote poems and tragedies. He is best remembered, however, as one of the Thirty Tyrants imposed on Athens by the Spartans. He was soon at odds with Theramenes, who was put to death. Critias earned a name for rapacity and bloodthirstiness, although Plato seems to have admired him, using him as a speaker in the dialogues Protagoras, Timaeus, and Critias. When Thrasybulus led his forces against the Thirty, Critias was killed in battle.