Alexandrian sophist of uncertain date, author of a collection of preliminary exercises (pro-gymnasmata) for the training of orators. The work (extant, though incomplete), which probably formed an appendix to a manual of rhetoric, shows learning and taste, and contains valuable notices on the style and speeches of the masters of Attic oratory. Theon also wrote commentaries on Xenophon, Isocrates and Demosthenes, and treatises on style. He is to be distinguished from the Stoic Theon, who lived in the time of Augustus and also wrote on rhetoric (Quintilian, Inst. Orat. ix. 3, 77).