The article discusses the question of the ethnonym Ῥουσ- in the Byzantine literature, attested in the tenth and eleventh centuries, either as part of an adjective, or in sources under Rus’ian influence, and then disappearing until the fifteenth century. In this connec- tion, the question arises whether the ethnonym Ῥούσιος actually existed, as documented by Liutprand of Cremona, but could be explained as an influence of the Latin language. The readers’ attention is drawn to the ethnonym Ῥούσιοι in the list of the peoples conquered by Alexander the Great, known in two manuscripts of the edition γ of the Greek Alexander Romance. Despite the presence of a number of fantastic peoples in this list, Ῥούσιοι were the real “barbarians” and, along with Χουνάβιοι, belonged to the source’s latest layer, dating from the tenth century. Several arguments make it necessary to identify them with Rus’. Thus, the first evidence of the ethnonym Ῥούσιοι appears on purely Greek soil, as well as the possibility to date this list of peoples. However, the use of the early ethnonym Ῥούσιοι allows the one to date to the period before the twelfth century this list of peoples from the edition γ of the Greek “Alexander Romance,” the earliest manuscripts of which date back to the fourteenth century.