The Erzincan valley crossed by the upper Euphrates was the location of the most important pre-Christian shrine in Armenia, dedicated to theArmenian goddess Anahit. The temple, whose site has not yet been identified, was in a settlement called Erez. The text of Agathangelos records that during the first year of his reign, King Trdat went to Erez and visited Anahit's temple to offer sacrifice. The king 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. After that conversion, during the Christianisation of Armenia, the temple at Erez was destroyed and its property and lands given to Gregory. It later became known for its extensive monasteries.
In 1071 Erzincan was absorbed into the Mengüçoğlu under the Seljuk Sulëiman Kutalmish. In 1243 it was destroyed in fighting between the Seljuks under Kaykhusraw II and the Mongols. However, by 1254 its population had recovered enough that William of Rubruck was able to say an earthquake had killed more than 10,000 people. During this period, the city reached a level of semi-independence under the rule of Armenian princes.
The city was completely destroyed by a major earthquake on December 27, 1939. The earthquake of seven violent shocks, the biggest one measuring 8.2 on the Richter scale, was the most powerful one to strike Turkey in recent history. The first stage of the earthquake killed about 8,000 people. The next day, it was reported that the death toll had risen to 20,000. An emergency relief operation began. By the end of the year, 32,962 had died due to more earthquakes and several floods. So extensive was the damage to Erzincan city that its old site was entirely abandoned and a new town was founded a little further to the north.