Erzincan is the capital of Erzincan Province in Eastern Turkey. The city is majority Sunni Turkish with a significant Alevi Kurdish minority.

Acilisene, the ancient city that is now Erzincan, was the site of the Peace of Acilisene by which in AD 387 Armenia was divided into two vassal states, a smaller one dependent on the Byzantine Empire and a larger one dependent on Persia. This is the name by which it is called by Strabo in his Geography. The etymological origin of the word is disputed, but it is agreed that the city was once called Erez. For a while it was called Justinianopolis in honour of Emperor Justinian. In more recent Greek it has been called as Keltzene and Kelezene.

In the Armenian language, the 5th-century Life of Mashtots called it Yekeghiats In the more recent past, it was known in Armenian as Yerznka.

In the settlement of Erez, at a yet unidentified site, there was a pre-Christian shrine dedicated to the Armenian goddess Anahit. A text of Agathangelos reports that during the first year of his reign, King Trdat of Armenia went to Erez and visited Anahit's temple to offer sacrifice. He ordered Gregory the Illuminator, who was secretly a Christian, to make an offering at its altar. When Gregory refused, he was taken captive and tortured, starting the events that would end with Trdat's conversion to Christianity some 14 years later.[10] After that conversion, during the Christianisation of Armenia, the temple at Erez was destroyed and its property and lands were given to Gregory. It later became known for its extensive monasteries.