The Azadan (Middle Persian:, Parthian: ; meaning 'free' and 'noble') were a class of Iranian nobles. They are probably identical to the ('the free ones') mentioned in Greek sources to refer to a group of Parthian nobles. According to the 1st-century Romano-Jewish historian Josephus (died 100 AD), the Parthian army led by prince Pacorus I during the invasion of Judea consisted of members of the . The Kingdom of Armenia adopted the same hierarchy as that of the Parthians, which included the class, which was used to label the Armenian middle and lower nobility. The name of the Georgian nobility,, also corresponded to that of . A class of are also attested in Sogdia, an Iranian civilization located in Central Asia.
The Sasanians, who supplanted the Parthians in 224, maintained the same divisions of the nobility as their predecessor. Under the Sasanians, the were members of the lower nobility and the last class-rank of the four types of the Sasanian nobility. The four ranks consisted of the (vassal kings and dynasts), the (princes of royal blood), the (grandees) and the (lower nobility). The and formed the bulk of the cavalry, which in turn formed the backbone of the Sasanian army. The were analogous to the knights of Medieval Europe.
The are first attested in the bilingual Hajjiabad inscription of the King of Kings Shapur I :
They are later mentioned in the Paikuli inscription of 293, erected by Shapur I's grandson Narseh, who mentions the along with other groups of the nobility. They are likewise mentioned in the inscription of Shapur II at Meshkinshahr. According to the 5th-century Byzantine Armenian historian Faustus of Byzantium, the formed the bulk of Shapur II's royal bodyguard regiment.