Timaeus of Locri was a Greek

Greeks

The Greeks, also known as the Hellenes , are a nation and ethnic group native to Greece, Cyprus and neighboring regions. They also form a significant diaspora, with Greek communities established around the world....

 Pythagorean

Pythagoreanism

Pythagoreanism was the system of esoteric and metaphysical beliefs held by Pythagoras and his followers, the Pythagoreans, who were considerably influenced by mathematics. Pythagoreanism originated in the 5th century BCE and greatly influenced Platonism...

 philosopher living in the 5th century BC.

He features in Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

's Timaeus

Timaeus (dialogue)

Timaeus is one of Plato's dialogues, mostly in the form of a long monologue given by the title character, written circa 360 BC. The work puts forward speculation on the nature of the physical world and human beings. It is followed by the dialogue Critias.Speakers of the dialogue are Socrates,...

, where he is said to come from Locri

Locri

Locri is a town and comune in the province of Reggio Calabria, Calabria, southern Italy. The name derives from the ancient Greek town Locris.-History:...

 in Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, thus of Locrian

Locrians

The Locrians were an ancient Greek tribe in Greece. The Locrians spoke the Locrian dialect, a Doric-Northwest dialect, which indicates that they may have been relatives of the Dorians. They inhabited the ancient region of Locris in Central Greece....

 origin.

He also appears as one of the speakers in Plato's Critias

Critias (dialogue)

Critias, one of Plato's late dialogues, contains the story of the mighty island kingdom Atlantis and its attempt to conquer Athens, which failed due to the ordered society of the Athenians...

.

Later references to Timaeus of Locri from Antiquity are by:

• Cicero
  Cicero
  Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...
  
  , in his De re publica
  De re publica
  De re publica is a dialogue on Roman politics by Cicero, written in six books between 54 and 51 BC. It is written in the format of a Socratic dialogue in which Scipio Africanus Minor takes the role of a wise old man — an obligatory part for the genre...
  
  (I, X, 16), where he is described as an intimate of Plato
  Plato
  Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...
  
  
• Proclus
  Proclus
  Proclus Lycaeus , called "The Successor" or "Diadochos" , was a Greek Neoplatonist philosopher, one of the last major Classical philosophers . He set forth one of the most elaborate and fully developed systems of Neoplatonism...
  
  , in his Commentary on Plato's Timaeus (II, 38, I)
• Simplicius
  Simplicius of Cilicia
  Simplicius of Cilicia, was a disciple of Ammonius Hermiae and Damascius, and was one of the last of the Neoplatonists. He was among the pagan philosophers persecuted by Justinian in the early 6th century, and was forced for a time to seek refuge in the Persian court, before being allowed back into...
  
   and Diogenes Laërtius
  Diogenes Laertius
  Diogenes Laertius was a biographer of the Greek philosophers. Nothing is known about his life, but his surviving Lives and Opinions of Eminent Philosophers is one of the principal surviving sources for the history of Greek philosophy.-Life:Nothing is definitively known about his life...
  
  , in their descriptions of, and commentaries on Aristotle
  Aristotle
  Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
  
  's work

All ancient references to him seem to have derived from Plato: he may well be a fictional character invented for the dialogue bearing his name (see M. F. Burnyeat).