While the only surviving legends of Cyrus the Great are found in Graeco-Roman sources, such sources ultimately speak to the varied views of Cyrus in Achaemenid Iran. Following a survey of the historical conditions leading to the rise of the Persian Empire under Cyrus and its consolidation under Darius, this article explores the characteristics of western Iranian historiography of the Median “state” and dawn of the Persian Empire in the Achaemenid period. This article argues that the Median and Iranian orientation of the Achaemenid Empire from the time of Darius provided the grounds for the infusing of Young Avestan myths and legends in western Iran. In particular, this article investigates parallels between stories of Cyrus the Great and those of Kauui Haosrauuah (Kay Khosrow); an investigation that points to the assimilation of the former with the latter that likely began in the Achaemenid period and later led to a two-way interaction of legends about these figures. In addition, this article also explores the Iranian tradition's depiction of Alexander and his association with Kay Khosrow, which is similar to his association with Cyrus the Great in western sources and may further show Cyrus the Great's assimilation with the Iranian tradition through his identification with Kay Khosrow.