Antiochus IX Eusebes Cyzicenus (Greek: Ἀντίοχος Εὐσεβής Κυζικηνός, "Antiochus the Pious, the Cyzicene") was a ruler of the Hellenistic Seleucid kingdom.

Antiochus VIII was assassinated in 96 BC; he was succeeded by his sons Seleucus VI and Demetrius III.

Antiochus IX Eusebes Cyzicenus was killed in battle in 95 B.C.

The son of Antiochus VII and Cleopatra Thea,[2] upon the death of his father in Parthia and his uncle Demetrius II's return to power (129 BC), his mother sent him to Cyzicus on the Bosporus, thus giving him his nickname.

[2] He returned to Syria in 116 BC to claim the Seleucid throne from Antiochus VIII, with whom he eventually divided Syria,[citation needed] that same year.