Pasion (Greek: Πασίων) was an ancient Greek slave from the 4th century BC. He was owned by the bankers Antisthenes and Archestratus, located at Piraeus, the harbor five miles out of Athens. During his slavery, he quickly rose to chief clerk in charge of a money-changing table at the port (Argyramoibos), and proved so valuable that he was finally freed in gratitude of his faithful service. When his owners retired, Pasion inherited the bank and established a shield factory. The gifts he provided Athens entailed one thousand shields and a trireme. Ultimately, Pasion was granted Athenian citizenship and started investing in real estate in order to accumulate more wealth. When he became too old to work, Pasion had Phormio, another slave, take care of the bank. When Pasion died, his widow married Phormio in order to keep the bank in the family.

Pasion's son, Apollodorus, did not engage in banking but lived off his inheritance like a gentleman; Pasion had left 20 talents in land and 40 in outstanding debt. Much of what we know about Pasion comes from speeches Apollodorus gave in lawsuits. These come down to us among the speeches Demosthenes wrote for litigants, but it is now thought that Apollodorus wrote them himself.