Antiochus II Theos (Greek: Αντίοχος Β' Θεός, 286 BC–246 BC), was a king of the Hellenistic Seleucid Kingdom who reigned 261 BC–246 BC). He succeeded his father Antiochus I Soter in the winter of 262-61 BC. He was the younger son of Antiochus I and princess Stratonice, the daughter of Demetrius Poliorcetes.
He inherited a state of war with Egypt, the "Second Syrian War", which was fought along the coasts of Asia Minor, and the constant intrigues of petty despots and restless city-states in Asia Minor. Antiochus also made some attempt to get a footing in Thrace. During the war he was given the title Theos (Greek: Θεός, "God"), being such to the Milesians in slaying the tyrant Timarchus.
During the time Antiochus was occupied with the war against Egypt, Andragoras, his satrap in Parthia, proclaimed independence. According to Justin's epitome of Pompeius Trogus, in Bactria, his satrap Diodotus also revolted in 255 BC, and founded the Greco-Bactrian kingdom, which further expanded in India in 180 BC to form the Greco-Indian kingdom (180 BC–1 BC). Then about 238 BC, Arsaces led a revolt of the Parthians against Andragoras, leading to the foundation of the Parthian Empire. These events would have cut off communications with India.
About this time, Antiochus made peace with Ptolemy II of Egypt, ending the Second Syrian War. Antiochus repudiated his wife Laodice I and exiled her to Ephesus. To seal the treaty, he married Ptolemy's daughter Berenice and received an enormous dowry.
During her stay in Ephesus, Laodice I continued numerous intrigues to become queen again. By 246 BC Antiochus had left Berenice and their infant son Antiochus, in Antioch to live again with Laodice I in Asia Minor. Laodice took the occasion to poison Antiochus while her partisans at Antioch murdered Berenice and their infant son.
Laodice I then proclaimed her own son Seleucus II Callinicus king. Among the children born to Antiochus II and Laodice I was, Laodice the wife of Mithridates II of Pontus.
Phylarchus relays current scandals regarding his drunken banquets and liaisons with unsuitable young men.