427 BC

Year 427 BC was a year of the pre-Julian Roman calendar.

• Sparta's King Archidamus II is succeeded by his son Agis II.
• Cleon says Mytilene must be destroyed. He decides not to kill the people.
• Plataea surrenders to the Spartans and Thebans. Over 200 prisoners are put to death and Plataea is destroyed.
• The civil war in Corcyra results in a victory of the democrats over the oligarchs.
• The Quaestorship is opened to the Plebs.

for more information, see Category:427 BC births.

• Plato, Greek philosopher (d. c. 347 BC)
• Xenophon, Greek historian, soldier, mercenary and an admirer of Socrates (d. 354 BC)

• Archidamus II, king of Sparta