Timaeus of Locri is a philosopher from the 5th century BCE, traditionally associated with the Pythagorean school in the Greek colony of Locri in Southern Italy. His historical existence is uncertain. He is primarily known as the character who delivers the cosmological lecture in Plato’s dialogue Timaeus. In that work, he is presented as an esteemed elder who explains the creation of the universe by a divine craftsman, the structure of the world soul, and the geometric nature of physical elements.

No authentic writings by a historical Timaeus survive. Two short works are attributed to him, but modern scholars consider them to be much later pseudepigrapha—texts falsely credited to a famous name. The most notable of these, On the Soul of the World and Nature, is a summary in Doric Greek of ideas from Plato’s Timaeus, likely composed centuries later. It was mistakenly believed in antiquity to be the original source for Plato’s theories.

Timaeus’s significance lies almost entirely in his literary role. As the speaker in Plato’s Timaeus, he became the iconic voice for Platonic and Pythagorean cosmology, a dialogue that profoundly influenced later Western science and philosophy. In later antiquity, the pseudepigraphical works helped forge a stronger link between Platonism and Pythagoreanism. Thus, his importance is not historical but symbolic, serving as a bridge between two major philosophical traditions.