in ancient Greece, the academy, or college, of philosophy in the northwestern outskirts of Athens, where Plato acquired property about 387 BC and used to teach. At the site there had been an olive grove, park, and gymnasium sacred to the legendary Attic hero Academus (or Hecademus).

The designation academy, as a school of philosophy, is usually applied not to Plato's immediate circle but to his successors down to the Roman Cicero's time (106–43 BC). Legally, the school was a corporate body organized for worship of the Muses, the scholarch (or headmaster) being elected for life by a majority vote of the members. Most scholars infer, mainly from Plato's writings, that instruction originally included mathematics, dialectics, natural science, and preparation for statesmanship. The Academy continued until AD 529, when the emperor Justinian closed it, together with the other pagan schools.

The Academy philosophically underwent various phases, arbitrarily classified as follows: (1) the Old Academy, under Plato and his immediate successors as scholarchs, when the philosophic thought there was moral, speculative, and dogmatic, (2) the Middle Academy, begun by Arcesilaus (316/315–c. 241 BC), who introduced a nondogmatic skepticism, and (3) the New Academy, founded by Carneades (2nd century BC), which ended with the scholarch Antiochus Of Ascalon (d. 68 BC), who effected a return to the dogmatism of the Old Academy. Thereafter, the Academy was a centre of Middle Platonism and Neoplatonism until it was closed in the 6th century AD.