Critias (/ˈkrɪtiəs/; Greek: Κριτίας, Kritias; c. 460 – 403 BCE) was an ancient Athenian political figure and author. Born in Athens, Critias was the son of Callaeschrus and a first cousin of Plato's mother Perictione. He became a leading and violent member of the Thirty Tyrants. He also was an associate of Socrates, a fact that did not endear Socrates to the Athenian public.
Critias was noted in his day for his tragedies, elegies and prose works. Some, like Sextus Empiricus, believe that Critias wrote the Sisyphus fragment; others, however, attribute it to Euripides. His only known play is Peirithous, of which only a single 42-line fragment survives (Sextus Empir. p. 403, 1). In addition, eight shorter quotations from unidentified plays have come down to us.
Critias gave an account of his ancestry which was later recorded in Plato's Timaeus. Critias's great-grandfather, Dropidas, was an intimate friend of Solon. Dropidas's son, also named Critias, is the grandfather and namesake of the author Critias.
Critias was once a student of Socrates. The two had a strained relationship. However, it is said that Critias was the one who saved Socrates from persecution during the terror of the Thirty Tyrants.
After the fall of Athens to the Spartans, Critias, as one of the Thirty Tyrants, blacklisted many of its citizens. Most of his prisoners were executed and their wealth confiscated.
Critias was killed in a battle near Piraeus, the port of Athens, between a band of pro-democracy Athenian exiles led by Thrasybulus and members and supporters of the Thirty, aided by the Spartan garrison. In the battle, the exiles put the oligarchic forces to flight, ending the rule of the Thirty.