Achaeus (died 213 BCE) is a general and later a separatist ruler of part of the Greek Seleucid kingdom.

He is the son of Andromachus, whose sister Laodice II, married Seleucus Callinicus, the father of Antiochus III the Great.

Achaeus himself marries Laodice of Pontus, one of the daughters to Laodice and Mithridates II of Pontus.