Kingdom of Osroene

Osroene, also spelled Osrohene and Osrhoene (Ancient Greek: Ὀσροηνή; Classical Syriac: ܡܠܟܘܬܐ ܕܒܝܬ ܐܘܪܗܝ Malkūṯā d-Bayt ʿŌrhai) and sometimes known by the name of its capital city, Edessa (modern Şanlıurfa, Turkey), was a historical kingdom located in Upper Mesopotamia,[1] which enjoyed semi-autonomy to complete independence from the years of 132 BC to AD 244.[2][3] It was a Syriac-speaking kingdom.[4]
Osroene, or Edessa, acquired independence from the collapsing Seleucid Empire through a dynasty of the nomadic Nabatean tribe called Orrhoei from 136 BC. The name Osroene is derived from Osroes of Orhai, a Nabatean malka who in 120 BC wrested control of this region from the Seleucids in Syria.[5] Most of the kings of Osroene are called Abgar or Manu who settled in urban centers.[6] Under its Nabatean dynasties, Osroëne became increasingly influenced by Syriac-Assyrian culture and was a centre of national reaction against Hellenism. By the 5th century, Edessa had become the headquarters of Syriac literature and learning.

Osreone was the first kingdom in history to have it's king declare Christianity the official religion. King Abgar the Great.