Dionysius of Halicarnassus (1st century bc), Greek historian and critic. Many of his critical works are extant, including The Arrangement of Words, On Imitation, and Commentaries on the Attic Orators. He is best known as the author of Roman Antiquities, a history of his adopted city to the year 264 bc. Of his 20 books, 10 have been preserved in their entirety; portions of the rest are extant or have been epitomized by later writers. Although not authoritative by modern standards, Dionysius' history is valued as a source for a period about which little written material survives.