Antiochus III the Great was a Greek Hellenistic king and the 6th ruler of the Seleucid Empire, reigning from 223 to 187 BC. He ruled over the region of Syria and large parts of the rest of western Asia towards the end of the 3rd century BC. Rising to the throne at the age of eighteen in April/June 223 BC, his early campaigns against the Ptolemaic Kingdom were unsuccessful, but in the following years Antiochus gained several military victories and substantially expanded the empire's territory. His traditional designation, the Great, reflects an epithet he assumed. He also assumed the title Basileus Megas, the traditional title of the Persian kings. A militarily active ruler, Antiochus restored much of the territory of the Seleucid Empire, before suffering a serious setback, towards the end of his reign, in his war against Rome.

The Seleucid Empire was a Greek power in West Asia during the Hellenistic period. It was founded in 312 BC by the Macedonian general Seleucus I Nicator, following the division of the Macedonian Empire founded by Alexander the Great, and ruled by the Seleucid dynasty until its annexation by the Roman Republic under Pompey in 63 BC.