Achaemenid Persia in the context of "Odrysian"

The Odrysian kingdom (/oʊˈdrɪʒən/; Ancient Greek: Βασίλειον Ὀδρυσῶν), also known as Odrysia, was an ancient Thracian state that thrived between the early 5th century BC and the early 3rd / late 1st century BC. Located in present-day Bulgaria, southeastern Romania (Northern Dobruja), northern Greece and European Turkey, it was a tribal amalgam dominated by the Odrysians that was the first large political entity to develop in the eastern Balkans.

The Odrysian kingdom was founded by king Teres I, who was exploiting the collapse of the Persian presence in Europe due to the failed invasion of Greece in 480–79. Teres and his son Sitalces pursued a policy of expansion, making the kingdom one of the most powerful of its time. Throughout much of its early history it remained an ally of Athens and even joined the Peloponnesian War on its side. By 400 BC the state showed first signs of fatigue, although the skilled Cotys I initiated a brief renaissance that lasted until his murder in 360 BC.

The Canon of Kings was a dated list of kings used by ancient astronomers as a convenient means to date astronomical phenomena, such as eclipses. For a period, the Canon was preserved by the astronomer Claudius Ptolemy, and is thus known sometimes as Ptolemy's Canon. It is one of the most important bases for modern knowledge of ancient chronology.

The Canon derives originally from Babylonian sources. Thus, it lists Kings of Babylon from 747 BC until the conquest of Babylon by Achaemenid Persians in 539 BC, and then Persian kings from 538 to 332 BC. At this point, the Canon was continued by Greek astronomers in Alexandria, and lists the Macedonian kings from 331 to 305 BC, the Ptolemies from 304 BC to 30 BC, and the Roman and Byzantine Emperors, although they are not kings; in some manuscripts the list is continued down to the Fall of Constantinople in 1453.