Antiochus II Theos (286–246 BC), was a king of the Hellenistic Seleucid Kingdom who reigned 261–246 BC). He succeeded his father Antiochus I Soter in 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, being such to the Milesians in slaying the tyrant Timarchus.

During the time Antiochus was tied with the war against Egypt, Andragoras, his satrap in Parthia, proclaimed indepence. 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 (180–1 BC). Then about 238 BC, Arsaces led a revolt of the Parthians against Andragoras, leading to the foundation of the Parthian Empire.

About this time, Antiochus made peace with Ptolemy II, ending the Second Syrian War. Antiochus repudiated his wife Laodice and banned her to Ephesus. To seal the treaty, he married Ptolemy's daughter Berenice and received an enormous dowry.

During her stay in Ephesus, Laodice continued numerous intrigues to become queen again. By 246 BC Antiochus had left Berenice and her infant son in Antioch to live again with Laodice in Asia Minor. Laodice took the occasion to poison Antiochus. while her partisans at Antioch murdered Berenice and her infant son.

She then proclaimed her own son Seleucus II Callinicus king.

Antiochus is mentionned in the Edicts of Ashoka, as one of the recipients of the Indian Emperor Ashoka's Buddhist proselytizing, although no Western historical record of this event remains: :"The conquest by Dharma has been won here, on the borders, and even six hundred yojanas (5,400-9,600 km) away, where the Greek king Antiochos rules, beyond there where the four kings named Ptolemy, Antigonos, Magas and Alexander rule, likewise in the south among the Cholas, the Pandyas, and as far as Tamraparni (Sri Lanka)." (Edicts of Ashoka, 13th Rock Edict, S. Dhammika).

Ashoka also claims that he encouraged the development of herbal medicine, for men and animals, in the territories of the Hellenistic kings: :"Everywhere within Beloved-of-the-Gods, King Piyadasi's [Ashoka's] domain, and among the people beyond the borders, the Cholas, the Pandyas, the Satiyaputras, the Keralaputras, as far as Tamraparni and where the Greek king Antiochos rules, and among the kings who are neighbors of Antiochos, everywhere has Beloved-of-the-Gods, King Piyadasi, made provision for two types of medical treatment: medical treatment for humans and medical treatment for animals. Wherever medical herbs suitable for humans or animals are not available, I have had them imported and grown. Wherever medical roots or fruits are not available I have had them imported and grown. Along roads I have had wells dug and trees planted for the benefit of humans and animals." Edicts of Ashoka, 2nd Rock Edict