Antioch on the Orontes (/ˈænti.ɒk/; Greek: Ἀντιόχεια ἡ ἐπὶ Ὀρόντου, Antiókheia hē epì Oróntou, .mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}pronounced [anti.ó.kʰeː.a])[note 1] was a Hellenistic Greek city[1][2] founded by Seleucus I Nicator in 300 BC.[3] It was one of the greatest and most important Greek cities of the Hellenistic period.[2] The city served as the capital of the Seleucid Empire and later as regional capital to both the Roman and Byzantine Empire. During the Crusades, Antioch served as the capital of the Principality of Antioch, one of four Crusader states that were founded in the Levant. Its inhabitants were known as Antiochenes. The modern city of Antakya, in Hatay Province of Turkey, was named after the ancient city, which lies in ruins on the Orontes River and did not overlap in habitation with the modern city.

Antioch was founded near the end of the fourth century BC by Seleucus I Nicator, one of Alexander the Great’s generals, as one of the tetrapoleis of Seleucis of Syria. Seleucus encouraged Greeks from all over the Mediterranean to settle in the city.[2] The city’s location offered geographical, military, and economic benefits to its occupants; Antioch was heavily involved in the spice trade and laid within close reach of the Silk Road and the Royal Road. The city was the capital of the Seleucid Empire from 240 BC until 63 BC, when the Romans took control, making it the capital of the province of Syria and later of Coele Syria. During the late Hellenistic and Roman Principate periods, Antioch’s population may have reached a peak of over 500,000 inhabitants (most generally estimate between 200,000 and 250,000),[4] making the city the third largest in the Roman Empire after Rome and Alexandria and one of the most important cities in the eastern Mediterranean. From the early fourth century, Antioch was the seat of the Count of the Orient, head of the Diocese of the East. The Romans provided the city with walls that encompassed almost 450 hectares (1,100 acres), of which one quarter was mountainous, leaving 300 ha (750 acres) – about one-fifth the area of Rome within the Aurelian Walls.