Kai Bahman or -Wahman (and other variants) is a mythological figure of Greater Iranian legend and lore. The stock epithet Kai identifies Bahman as one of the Kayanian kings of Iranian oral tradition.
He can be identified with both Achaemenid kings Artaxerxes I and Cyrus the Great, and may be regarded as a mixture of the two.
In the genealogy of the legendary dynasty, Bahman is the son of Esfandiyar (hence his also being referred to in Middle Persian as 'Vohuman Asfandyar'), grandson of Goshtasp, husband of [his own daughter] Komani/Homai, and father of Dara/Darab. Other details vary: Several different Arabic and Persian sources (e.g. al-Tabari and ibn al-Balkhi) assert that Bahman had five children; two sons, Dara/Darab and Sasan/Sassan, and three daughters, Komani/Homai (stock epithet: Chehrazad), Bahmandokht and Farnak.
In the Bahman-nama (composed ca. 1100 CE, not to be confused with a 15th-century hagiography of the Deccan Bahmanids) Bahman is portrayed as being asked by Rostam to marry Katayun/Kasayun, daughter of the King of Kashmir. Bahman does so, but subsequently has to flee to Egypt where he marries Homai, the daughter of the Egyptian king, with whom he has a daughter also named Homai. Other sources have Bahman marrying his own daughter Komani/Homai on account of her great beauty, and that Dara/Darab was the result of this union. In one tradition (reiterated by ibn al-Balkhi), the marriage was denied and Homai dies a spinster.
The name 'Bahman'/'Wahman' is a theophoric reflecting Middle Persian Vohuman, Avestan Vohu Manah, the Amesha Spenta (Ameshaspand) that is the hypostasis of the "Good Mind" or "Good Disposition." Unlike most figures of Iranian oral tradition, Bahman does not however appear in the surviving Avesta. He is however referred to in the Zand-i Wahman yasn (also known as the Bahman Yasht, which—despite that name—is not an Avestan Yasht, but a medieval pseudo-prophetic/apocaplyptic text). The figure is also mentioned in the 9-11th century texts of Zoroastrian tradition, specifically, the Middle Persian Bundahishn (GBd 36.9) and the Denkard (VII.6), both of which enumerate the Kayanian kings. In both the Zand-i Vohuman Yasht (3.20-29) and the Denkard, Bahman is described as "one of the greatest Mazdayasnian kings of Iran."