Nusaybin (; ; ; ), historically known as Nisibis () or Nesbin, is a city and the seat of the Nusaybin District of the Mardin Province in Turkey. The city is populated by Kurds of different tribal affiliation and had a population of 84,445 in 2021. Nusaybin is separated from the larger Kurdish-majority city of Qamishli by the Syria–Turkey border. The city is at the foot of the Mount Izla escarpment at the southern edge of the Tur Abdin hills, standing on the banks of the Jaghjagh River (), the ancient Mygdonius (). The city existed in the Assyrian Empire and is recorded in Akkadian inscriptions as Naṣibīna. Having been part of the Achaemenid Empire, in the Hellenistic period the settlement was re-founded as a polis named "Antioch on the Mygdonius" by the Seleucid dynasty after the conquests of Alexander the Great. A part of first the Roman Republic and then the Roman Empire, the city (; ) was mainly Syriac-speaking, and control of it was contested between the Kingdom of Armenia, the Romans, and the Parthian Empire. After a peace treaty contracted between the Sasanian Empire and the Romans in 298 and enduring until 337, Nisibis was capital of Roman Mesopotamia and the seat of its governor (). Jacob of Nisibis, the city's first known bishop, constructed its first cathedral between 313 and 320. Nisibis was a focus of international trade, and according to the Greek history of Peter the Patrician, the primary point of contact between Roman and Persian empires. Nisibis was besieged three times by the Sasanian army under Shapur II () in the first half of the 4th century; each time, the city's fortifications held. The Syriac poet Ephrem the Syrian witnessed all three sieges, and praised Nisibis's successive bishops for their contributions to the defences in his , while the Roman caesar Julian () described the third siege in his panegyric to his senior co-emperor, the augustus Constantius II (). The Roman soldier and Latin historian Ammianus Marcellinus described Nisibis, fortified with walls, towers, and a citadel, as "the strongest bulwark of the Orient". After the defeat of the Romans in Julian's Persian War, Julian's successor Jovian () was forced to cede the five Transtigritine provinces to the Persians, including Nisibis. The city was evacuated and its citizens forced to migrate to Amida (Diyarbakır) – which was expanded to accommodate them – and to Edessa