Sāssān (Middle Iranian > Persian ساسان, also known as Sasan), considered the eponymous ancestor of the Sasanian (or Sassanid) Dynasty, was "a great warrior and hunter" and a Zoroastrian high priest in Pars who lived some time near the fall of the Arsacid (Parthian) Empire.
There are many slightly different stories concerning Sasan and his relation to Ardashir I, the founder of the Sasanian Empire. The northern Iranian historian Tabari mentions that Sasan married a princess of the Bāzarangid family, the vassal dynasty of Pārs, and that Sasan was a grandfather of Ardashir I, while Papak is named as Ardashir I's father.
According to the Pahlavi book of Karnamak-i Artaxshir-i Papakan, Sasan's wife was a daughter of a nobleman called Papak. The marriage was arranged by Papak after hearing that Sasan has "Achamenian (Achaemenid) blood in him". Their son was Ardashir I. Sasan vanishes shortly after Ardashir appears in the story and Papak is "considered the father of Ardashir".
These stories on different relations between Ardashir, Pāpak, and Sāsān have, according to Frye, a Zoroastrian explanation. Sasan was indeed the father of Ardashir and "disappears" from the story after the birth of Ardashir. Similar to the current Zoroastrian practices, Papak had then taken the responsibility of his daughter and her son Ardashir after Sasan "disappears" and is named afterwards as the father of Ardashir.
In the Kabe Zartosht inscription of Shapur I the Great, the four named persons "Sasan, Papak, Ardashir, Shapur" have different titles: Sasan is named as hwataw or xwadāy ("the lord", usually given to sovereigns of small local principalities), Papak as shah, Ardashir as shāhanshāh ("King of Kings of the Sasanian Empire") and Shapur as "King of Kings of Iran and Aniran".