Pabag (, Pāpak/Pābag; New Persian: Bābak), was an Iranian prince who ruled Istakhr, the capital of Pars, from 205 or 206 until his death sometime between 207–210. He was the father, stepfather, grandfather, or father-in-law of Ardashir I, the founder of the Sasanian Empire. He was succeeded by his eldest son Shapur. Background and state of Pars Pars (also known as Persis), a region in the southwestern Iranian plateau, was the homeland of a southwestern branch of the Iranian peoples, the Persians. It also was also the birthplace of the first Iranian Empire, the Achaemenids. The region served as the center of the empire until its conquest by the Macedonian king Alexander the Great (). Since the end of the 3rd or the beginning of the 2nd century BCE, Pars was ruled by local dynasts subject to the Hellenistic Seleucid Empire. These dynasts held the ancient Persian title of frataraka ("leader, governor, forerunner"), which is also attested in the Achaemenid-era. Later under the frataraka Wadfradad II (fl. 138 BC), Pars was made a vassal of the Iranian Parthian (Arsacid) Empire. The frataraka were shortly afterwards replaced by the Kings of Persis, most likely at the accession of the Arsacid monarch Phraates II (). Unlike the fratarakas, the Kings of Persis used the title of shah ("king"), and laid foundations to a new dynasty, which may be labelled the Darayanids. Origins New Persian and Arabic texts There are various different sources regarding the relationship between Pabag, Sasan, and the first Sasanian monarch Ardashir I (). According to the Shahnameh ("The Book of Kings") by the medieval Persian poet Ferdowsi (d. 1020), Sasan was a descendant of the mythological Kayanian rulers Dara II, Dara I, Kay Bahman, Esfandiyar and Vishtaspa. The claim of Sasan belonging to the Kayanian family was designed in order to justify that Ardashir was descended from the ancient Kayanian kings, who reflected memories of the Achaemenids. Dara II, the last Kayanian king to rule before Alexander, is partly based on the last Achaemenid King of Kings, Darius III (), whose empire was indeed conquered by Alexander's forces. A son of Dara II named Sasan (called "the elder") fled to India and lived there in exile until his death. He was survived by a son who was likewise named Sasan (called "the younger"), "which continued in the family for four generations". A descendant of the family, likewise named Sasan,