Dionysius Thrax (Διονυσιος Θραξ) (170 BC‑90 BC) was a Greek linguist who lived and is thought by some to have worked in Alexandria and later at Rhodes.

He collected the knowledge of the time on language and grammar. His main work on language is "Techne grammatice" (http://www.fh-augsburg.de/~harsch/graeca/Chronologia/S_ante02/DionysiosThrax/dio_tec0.html).