Stephanus or Stephan of Byzantium (Latin: Stephanus Byzantinus; Greek: Στέφανος Βυζάντιος, Stéphanos Byzántios; fl. 6th century AD), was a Byzantine grammarian and the author of an important geographical dictionary entitled Ethnica (Ἐθνικά). Only meagre fragments of the dictionary survive, but the epitome is extant, compiled by one Hermolaus, not otherwise identified.
Nothing is known about the life of Stephanus, except that he was a Greek grammarian who was active in Constantinople, and lived after the time of Arcadius and Honorius, and before that of Justinian II. Later writers provide no information about him, but they do note that the work was later reduced to an epitome by a certain Hermolaus, who dedicated his epitome to Justinian; whether the first or second emperor of that name is meant is disputed, but it seems probable that Stephanus flourished in Byzantium in the earlier part of the sixth century AD, under Justinian I.
Even as an epitome, the Ethnica is of enormous value for geographical, mythological, and religious information about ancient Greece. Nearly every article in the epitome contains a reference to some ancient writer, as an authority for the name of the place. From the surviving fragments, we see that the original contained considerable quotations from ancient authors, besides many interesting particulars, topographical, historical, mythological, and others. Stephanus cites Artemidorus, Polybius, Aelius Herodianus, Herodotus, Thucydides, Xenophon, Strabo and other writers.
The chief fragments remaining of the original work are preserved by Constantine Porphyrogennetos, De administrando imperio, ch. 23 (the article Ίβηρίαι δύο) and De thematibus, ii. 10 (an account of Sicily); the latter includes a passage from the comic poet Alexis on the Seven Largest Islands. Another respectable fragment, from the article Δύμη to the end of Δ, exists in a manuscript of the Fonds Coislin, the library formed by Pierre Séguier.
The first modern printed edition of the work was that published by the Aldine Press in Venice, 1502. The complete standard edition is still that of Augustus Meineke (1849, reprinted at Graz, 1958), and by convention, references to the text use Meineke's page numbers. A new completely revised edition in German, edited by B. Wyss, C. Zubler, M. Billerbeck, J.F. Gaertner, was published between 2006 and 2017, with a total of 5 volumes.