Timaeus the Sophist (Greek: Τίμαιος ὁ Σοφιστής) was a Greek philosopher who lived sometime between the 1st and 4th centuries. Nothing is known about his life.
He is the supposed author of a Lexicon of Platonic words, which is still extant. The purpose of the Lexicon was to explain the usage of words and phrases which occur in Plato's works, and made use of earlier commentaries on Plato which are now lost. It underwent significant additions and subtractions of text during later periods leading to the inclusion of many words which have nothing to do with Plato or his philosophy. The first complete edition of the Lexicon, prepared by David Ruhnken, was published in Leiden in 1754.