Antiochus I Soter
Achaeus (; flourished 3rd century BC) was a Greek Macedonian nobleman and was the second son born to King and founder of the Seleucid Empire Seleucus I Nicator and Persian noblewoman Apama I. Achaeus was of Greek and Persian descent. He had three siblings: one brother the Seleucid King Antiochus I Soter and two sisters: Apama and Laodice. Achaeus is sometimes called "Achaeus the Elder", to distinguish him from his grandson the Seleucid General, Achaeus.