Simon Psellus (Greek: Σίμων ὁ Ψελλός, his epithet Ψελλός was his nickname meaning in Greek: the stutter, flourished 2nd century BC) was an ethnic Jew living in Jerusalem.
Simon's ancestors were contemporary to the rule of the Ptolemaic dynasty and Seleucid dynasty over Judea. He was a wealthy man who served as a priest in the Temple in Jerusalem. Simon belonged to the priestly order of the Jehoiarib, the first of the twenty-four orders of Priests in the Temple in Jerusalem. Simon lived when the Hasmonean rulers Simon Thassi (reigned 142–135 BC) and his son John Hyrcanus I (reigned 134–104 BC) ruled over Judea.
Simon had nine children; among them was his son Matthias Ephlias. Through his son, Simon was an ancestor of the Roman Jewish Historian of the 1st century, Flavius Josephus. Josephus in his writings calls Simon the Patriarch of his family.