Adiabene (Greek: Αδιαβηνή, Classical Syriac: ܚܕܝܐܒ) was an ancient kingdom in northern Mesopotamia, corresponding to the northwestern part of ancient Assyria. The size of the kingdom varied over time; initially encompassing an area between the Zab Rivers, it eventually gained control of Nineveh and starting at least with the rule of Monobazos I (late 1st-century BCE), Gordyene became an Adiabenian dependency. It reached its zenith under Izates II, who was granted the district of Nisibis by the Parthian king Artabanus II (r. 12–40) as a reward for helping him regain his throne. Adiabene's eastern borders stopped at the Zagros Mountains, adjacent to the region of Media. Arbela served as the capital of Adiabene.
The formation of the kingdom is obscure. The first instance of a recorded Adiabenian ruler is in 69 BCE, when an unnamed king of Adiabene participated in the battle of Tigranocerta as an ally of the Armenian king Tigranes the Great (r. 95–55 BCE). However, coinage implies the establishment of a kingdom in Adiabene around 164 BCE, following the disintegration of Greek Seleucid rule in the Near East. Adiabene was conquered by the Parthian king Mithridates I (r. 171–132 BCE) between 145–141 BCE, and served at least from the reign of Mithridates II (r. 124–91 BCE) as an integral part of the Parthian realm.
