Antiochus II Theos (286–246 BC; reigned 261–246 BC) succeeded his father Antiochus I Soter as head of the Seleucid dynasty on 261 BC. He was the son of Antiochus I and princess Stratonice, the daughter of Demetrius Poliorcetes

He inherited a state of war with Egypt, which was fought along the coasts of Asia Minor (the "Second Syrian War"). Antiochus also made some attempt to get a footing in Thrace. During the war he was given the title "Theos" which means "God" in Greek.

In Bactria, his satrap Diodotus revolted in 255 BC, and founded the Greco-Bactrian kingdom, which further expanded in India in 180 BC to form the Greco-Indian kingdom (180–1 BC). Then about 250 BC, Arsaces led a revolt of the Parthians, which deprived him of those territories.

About this time, Antiochus made peace with Ptolemy II, ending the Second Syrian War. Antiochus repudiated his wife Laodice and married Ptolemy's daughter Berenice to seal their treaty, but by 246 BC Antiochus had left Berenice and her infant son in Antioch to live again with Laodice in Asia Minor.

Laodice poisoned him and proclaimed her son Seleucus II Callinicus king.