In Athens, Plato founded the Academy, a philosophical school where he taught the philosophical doctrines that would later become known as Platonism. Plato, or Platon, was a pen name derived, apparently, from the nickname given to him by his wrestling coach – allegedly a reference to his physical girth. According to Alexander Polyhistor, quoted by Diogenes Laërtius, his actual name was Aristocles, son of Ariston, of the deme (suburb) Collytus, in Athens.

Plato was an innovator of the written dialogue and dialectic forms in philosophy. He raised problems for what became all the major areas of both theoretical philosophy and practical philosophy. His most famous contribution is the theory of forms (or ideas), which has been interpreted as advancing a solution to what is now known as the problem of universals. He is the namesake of Platonic love and the Platonic solids. His own most decisive philosophical influences are usually thought to have been, along with Socrates, the pre-Socratics Pythagoras, Heraclitus, and Parmenides, although few of his predecessors' works remain extant and much of what is known about these figures today derives from Plato himself.