Chabrias (died 356 bc, Chios, Ionia) was a mercenary who fought with distinction for the Athenians against various enemies and for the kings of Cyprus and Egypt.
Chabrias defeated the Spartans in 388 and again in 378, when Athens joined Thebes against Sparta. On the latter occasion he invented a new defensive technique: he ordered each soldier to receive a charge kneeling on his left knee, with his shield resting on the ground and spear pointed at the enemy. In 366 he was accused of treachery but was acquitted, and in about 361 he accepted a command under King Tachos of Egypt. At the outbreak of the Social War (357–355; Athens versus its allies of the second Athenian Confederation), Chabrias served with the Athenian fleet. He lost his life in a naval battle near the island of Chios, off the coast of Ionia.